MANAGEMENT AND CONTROL OF INVENTORIES (DRUGS) IN GOVERNMENT HEALTH INSTITUTIONS

CHAPTER ONE: INTRODUCTION

1.1 Background of the Study

Inventory management and control is a critical function in any organization that holds stock of goods or materials, but it assumes even greater significance in health institutions. In government health institutions—hospitals, clinics, health centers, and medical stores—inventory primarily consists of pharmaceutical products (drugs, vaccines, sera), medical supplies (syringes, gloves, bandages), surgical equipment, laboratory reagents, and other consumables. Effective management and control of these inventories ensure that patients receive timely and appropriate medical treatment, that scarce public resources are used efficiently, that drugs do not expire before use, and that stock-outs (shortages) do not occur. Conversely, poor inventory management can lead to drug shortages that endanger patient lives, expiration and wastage of costly pharmaceuticals, theft and diversion of drugs, and significant financial losses (WHO, 2019; MSH, 2020).

The management and control of drug inventories in government health institutions involves a series of interconnected processes: procurement (ordering drugs from manufacturers or suppliers), receipt and inspection (verifying quantity and quality), storage (maintaining appropriate temperature, humidity, and security), inventory tracking (recording receipts, issues, and balances), dispensing (providing drugs to patients), monitoring (tracking expiration dates, consumption patterns, and stock levels), and disposal (destroying expired or damaged drugs). Each of these processes requires specific procedures, trained personnel, and appropriate infrastructure. Weaknesses in any link in this chain can compromise the entire system, leading to drug shortages, wastage, or diversion (MSH, 2020; WHO, 2019).

Government health institutions in Nigeria face unique challenges in drug inventory management. These include inadequate funding for drug procurement, resulting in chronic shortages; weak supply chain systems, with poor record-keeping and lack of real-time inventory visibility; storage facilities that lack proper temperature control (cold chain for vaccines and temperature-sensitive drugs), leading to spoilage; theft and diversion of drugs for private sale; expiration of drugs before use due to overstocking or slow consumption; lack of trained pharmacy staff and inventory managers; and corruption in procurement, where substandard or overpriced drugs are purchased. The consequences of these challenges are severe: patients may be unable to access essential medicines, public funds are wasted on expired or stolen drugs, and trust in the public health system erodes (Adebayo and Oyedokun, 2019; Okafor and Udeh, 2020).

The term “inventory” in the context of government health institutions refers to the stock of all pharmaceutical products and medical supplies held for eventual distribution or use. This includes essential drugs (antibiotics, antimalarials, antihypertensives, insulin, etc.), vaccines (which require strict temperature control), controlled substances (narcotics and psychotropics, which require special security), and medical consumables. The value of drug inventories in a typical government hospital can run into millions of Naira, representing a significant portion of the health institution’s operating budget. Effective inventory management is therefore not only a clinical necessity but also a financial imperative (MSH, 2020; WHO, 2019).

Inventory control refers to the systems, procedures, and practices designed to ensure that the right quantity of drugs is available at the right time, in the right place, in the right condition, at the right cost. Key principles of inventory control include: maintaining accurate records of receipts and issues; setting minimum and maximum stock levels to trigger reordering; conducting regular physical counts to verify records; using the First-Expiry-First-Out (FEFO) method to ensure older stock is used before it expires; securing storage areas against theft; and monitoring consumption patterns to forecast future needs. In government health institutions, inventory control is typically the responsibility of the pharmacy department, with oversight from the hospital management and, at higher levels, from state and federal ministries of health (MSH, 2020; WHO, 2019).

The management of drug inventories in government health institutions is governed by multiple policies and regulations. At the federal level, the National Drug Policy (NDP) provides guidelines for drug procurement, storage, distribution, and use in public health facilities. The National Agency for Food and Drug Administration and Control (NAFDAC) regulates drug quality and safety, including registration, inspection, and post-market surveillance. The Pharmacists Council of Nigeria (PCN) regulates the practice of pharmacy, including inventory management standards. State ministries of health issue additional guidelines for health facilities under their jurisdiction. Despite this regulatory framework, compliance is often weak, and enforcement is inconsistent (Federal Ministry of Health, 2018; NAFDAC, 2020).

One of the most critical aspects of drug inventory management is the maintenance of the cold chain. Many drugs, particularly vaccines and certain biologics, must be stored at specific temperatures (typically 2-8°C) to remain effective. If the cold chain is broken (e.g., due to power outages, refrigerator failure, or improper handling), the drugs may become ineffective, and administering them could be dangerous. In Nigeria, unreliable electricity supply is a major challenge for cold chain maintenance in government health institutions. Many facilities rely on generators or solar-powered refrigerators, but fuel shortages and maintenance issues can still lead to cold chain breaches. The cost of replacing expired vaccines and temperature-sensitive drugs due to cold chain failures is substantial (WHO, 2019; MSH, 2020).

The theft and diversion of drugs from government health institutions is a persistent problem. Drugs are valuable commodities, and there is a ready black market for pharmaceuticals. Staff may steal drugs for personal use, for sale to private pharmacies, or for supply to unauthorized outlets. Controlled substances (narcotics, psychotropics) are particularly vulnerable to diversion. Weak inventory controls—such as lack of physical security, inadequate supervision, poor record-keeping, and lack of independent audits—facilitate theft. The financial loss from drug theft is significant, but the patient impact is even greater: when drugs are stolen, they are not available for patients who need them (Adebayo and Oyedokun, 2019; Okafor and Udeh, 2020).

The role of pharmacy staff in inventory management cannot be overstated. Pharmacists and pharmacy technicians are trained in drug storage, inventory management, and dispensing. However, many government health institutions face shortages of qualified pharmacy personnel. A single pharmacist may be responsible for the entire inventory of a large hospital, making it impossible to maintain accurate records, conduct regular stock counts, and supervise dispensing. Low salaries, poor working conditions, and limited career advancement opportunities contribute to high turnover and difficulty attracting qualified staff to rural or underserved areas (Nwankwo and Okeke, 2020; Eze and Nwafor, 2019).

Government health institutions can be classified into primary (health centers, clinics), secondary (general hospitals), and tertiary (teaching hospitals, federal medical centers) levels. Inventory management challenges vary by level. Primary facilities may lack even basic storage facilities (refrigerators, shelves, secure cabinets) and trained staff. Secondary facilities may have better infrastructure but still face procurement delays and record-keeping challenges. Tertiary facilities, which handle larger volumes and more specialized drugs, may have more sophisticated systems but also face greater complexity. A comprehensive understanding of inventory management must consider these different levels (Federal Ministry of Health, 2018).

Technology offers significant prospects for improving drug inventory management in government health institutions. Electronic logistics management information systems (eLMIS) can provide real-time visibility of stock levels across multiple facilities, automate reordering, generate alerts for low stock or approaching expiration, and produce consumption reports for forecasting. Barcode scanning can reduce data entry errors and speed up inventory transactions. Mobile phones can be used to report stock levels from remote facilities (mobile data collection). Cloud-based systems allow centralized monitoring and coordination. However, implementing these technologies in government health institutions requires investment, infrastructure (electricity, internet), training, and change management—all of which are significant challenges (Okafor and Udeh, 2021; Eze and Nwafor, 2020).

1.2 Statement of the Problem

Government health institutions in Nigeria face persistent and significant challenges in the management and control of drug inventories. Evidence from audit reports, health facility assessments, and media reports indicates widespread problems including: frequent stock-outs of essential medicines, expiration and wastage of costly drugs, theft and diversion of pharmaceuticals, poor storage conditions (including cold chain failures), inaccurate inventory records, lack of real-time visibility of stock levels, delays in procurement, and inadequate supervision of pharmacy staff. These problems have serious consequences: patients are denied access to life-saving medications, public funds are wasted on expired or stolen drugs, health workers are demoralized, and trust in the public health system erodes. While the problems are well-documented anecdotally, there is a lack of systematic, empirical research that identifies the root causes of these inventory management failures, assesses the effectiveness of current control systems, and identifies realistic prospects for improvement. Furthermore, the specific inventory management challenges vary across different levels of government health institutions (primary, secondary, tertiary), but these variations are not well understood. Therefore, this study is motivated to investigate the management and control of drug inventories in government health institutions, to identify the specific problems and their causes, to assess current practices, and to propose evidence-based recommendations for improvement.

1.3 Aim of the Study

The aim of this study is to examine the management and control of inventories (drugs) in government health institutions, with a focus on identifying problems, assessing current practices, and identifying prospects for improvement.

1.4 Objectives of the Study

The specific objectives of this study are to:

1. Examine the current inventory management and control practices for drugs in government health institutions.
2. Identify the specific problems and challenges affecting drug inventory management in these institutions.
3. Assess the effectiveness of existing inventory control systems (including manual and computerized systems) in ensuring drug availability and minimizing wastage.
4. Evaluate the impact of poor inventory management on patient care, drug availability, and financial resources.
5. Identify the prospects and opportunities for improving drug inventory management and propose practical recommendations for government health institutions.

1.5 Research Questions

The following research questions guide this study:

1. What are the current inventory management and control practices for drugs in government health institutions?
2. What are the major problems and challenges affecting drug inventory management in these institutions?
3. How effective are existing inventory control systems in ensuring drug availability and minimizing wastage?
4. What is the impact of poor inventory management on patient care, drug availability, and financial resources?
5. What prospects and opportunities exist for improving drug inventory management in government health institutions?

1.6 Research Hypotheses

Hypothesis One

• H₀: Inadequate storage facilities (including cold chain) have no significant effect on drug wastage due to expiration and spoilage in government health institutions.
• H₁: Inadequate storage facilities (including cold chain) have a significant effect on drug wastage due to expiration and spoilage in government health institutions.

Hypothesis Two

• H₀: There is no significant relationship between poor record-keeping and the incidence of drug theft and diversion in government health institutions.
• H₁: There is a significant relationship between poor record-keeping and the incidence of drug theft and diversion in government health institutions.

Hypothesis Three

• H₀: Inaccurate demand forecasting and procurement delays do not significantly contribute to drug stock-outs in government health institutions.
• H₁: Inaccurate demand forecasting and procurement delays significantly contribute to drug stock-outs in government health institutions.

Hypothesis Four

• H₀: Staff shortages and lack of training have no significant effect on the effectiveness of drug inventory management in government health institutions.
• H₁: Staff shortages and lack of training have a significant effect on the effectiveness of drug inventory management in government health institutions.

1.7 Significance of the Study

This study is significant for several stakeholders. First, the management of government health institutions (hospitals, clinics, health centers) will benefit from a systematic assessment of drug inventory management problems and prospects, enabling them to strengthen control systems, reduce wastage, and improve drug availability. Second, pharmacy staff (pharmacists, pharmacy technicians, and storekeepers) will gain insights into best practices and common pitfalls, supporting their professional development and daily work. Third, state and federal ministries of health will benefit from evidence on inventory management challenges across different levels of the health system, informing policy, resource allocation, and supervision. Fourth, the National Agency for Food and Drug Administration and Control (NAFDAC) and the Pharmacists Council of Nigeria (PCN) will gain insights into compliance gaps, informing regulatory enforcement and capacity-building programs. Fifth, international development partners (WHO, UNICEF, World Bank, USAID) will gain insights into the implementation challenges of drug supply chain reforms in Nigeria, informing technical assistance and program design. Sixth, academics and researchers in public health, health systems, and supply chain management will find value in the study’s contribution to the literature on pharmaceutical inventory management in low-resource settings. Finally, patients and the general public will benefit indirectly as improved drug inventory management leads to better availability of essential medicines, reduced out-of-pocket expenditures for drugs, and improved health outcomes.

1.8 Scope of the Study

This study focuses on the management and control of inventories (drugs) in government health institutions. The study covers government-owned health facilities, including primary health centers (PHCs), general hospitals, and tertiary hospitals (teaching hospitals, federal medical centers). Geographically, the research is limited to selected government health institutions within a defined area. Content-wise, the study examines inventory management practices (procurement, receipt, storage, tracking, dispensing, disposal), inventory control systems (manual vs. computerized, stock cards, security, FEFO), problems (stock-outs, expiration, theft, cold chain failures, staff shortages), prospects (technology, training, policy reforms), and impact on patient care and resources. The study targets health facility managers, pharmacy staff, storekeepers, and administrative staff. The time frame for data collection is the cross-sectional period of 2023–2024. The study does not cover private health institutions nor other types of inventory (medical equipment, non-drug supplies).

1.9 Definition of Terms

Inventory Management: The process of overseeing and controlling the ordering, storage, and use of drugs, including procurement, receipt, storage, tracking, dispensing, and disposal.

Inventory Control: The systems, procedures, and practices designed to ensure the right quantity of drugs is available at the right time, in the right condition, at the right cost.

Government Health Institution: A health facility owned, funded, and operated by the government (federal, state, or local), including primary health centers, general hospitals, and tertiary hospitals.

Drugs: Pharmaceutical products, including prescription medications, over-the-counter medicines, vaccines, sera, and other therapeutic substances.

Stock-out: A situation where a particular drug is not available in inventory when needed for patient treatment.

Expiration (Drug Expiry): The date after which a pharmaceutical product should not be used because its safety, efficacy, or potency may be compromised.

Wastage: Loss of drugs due to expiration, spoilage, damage, theft, or other causes.

Cold Chain: The temperature-controlled supply chain required for vaccines and certain drugs that must be stored within a specific temperature range (typically 2-8°C).

First-Expiry-First-Out (FEFO): An inventory management method where drugs with the earliest expiration dates are used first.

Stock Card (Bin Card): A manual record-keeping tool recording receipts, issues, and balances of a specific drug.

Diversion (Drug Diversion): The transfer of legally prescribed drugs from legitimate channels to illicit channels, including theft by staff.

Essential Medicines: A core list of drugs that satisfy priority healthcare needs of the population.

CHAPTER TWO: LITERATURE REVIEW

2.1 Conceptual Framework

A conceptual framework is a structural representation of the key concepts or variables in a study and the hypothesized relationships among them. It serves as the analytical lens through which the researcher organizes the study, selects appropriate methodology, and interprets findings. In this study, the conceptual framework is built around three primary constructs: Inventory Management Practices (the independent variable), Inventory Control Systems (the mediating variable), and Inventory Management Outcomes (the dependent variable). Additionally, the framework identifies the specific dimensions of each construct and the moderating variables that influence the relationships (Miles, Huberman, and Saldaña, 2020).

The independent variable, Inventory Management Practices, refers to the methods, procedures, and activities used by government health institutions to manage their drug inventories. For the purpose of this study, inventory management practices are conceptualized along six key dimensions: (a) procurement practices (processes for ordering drugs from suppliers, including quantification, tendering, and contracting), (b) receiving and inspection practices (verifying quantity, quality, and condition of drugs upon delivery), (c) storage practices (arranging drugs in storage areas, maintaining appropriate temperature and humidity, ensuring security), (d) inventory tracking practices (recording receipts, issues, and balances using stock cards, bin cards, or electronic systems), (e) dispensing practices (providing drugs to patients and recording the transaction), and (f) disposal practices (removing expired, damaged, or recalled drugs from inventory and destroying them properly). Each dimension contributes differently to overall inventory management effectiveness (MSH, 2020; WHO, 2019).

The mediating variable, Inventory Control Systems, refers to the tools, technologies, and procedures specifically designed to monitor and regulate inventory levels. For the purpose of this study, inventory control systems are conceptualized along five key types: (a) manual stock control systems (using paper-based stock cards, bin cards, and ledgers), (b) computerized inventory management systems (using software to track stock levels, generate reorder alerts, and produce reports), (c) physical security controls (locks, access restrictions, surveillance), (d) inventory counting and verification controls (periodic physical counts, cycle counting, reconciliation), and (e) FEFO (First-Expiry-First-Out) and FIFO (First-In-First-Out) systems (methods for rotating stock to minimize expiration). These control systems mediate the relationship between management practices and outcomes (MSH, 2020; Okafor and Udeh, 2021).

The dependent variable, Inventory Management Outcomes, refers to the results or consequences of inventory management and control in government health institutions. For the purpose of this study, outcomes are conceptualized along four key dimensions: (a) drug availability (the extent to which essential drugs are in stock when needed for patients), (b) drug wastage (the loss of drugs due to expiration, spoilage, damage, or theft), (c) financial efficiency (the cost-effectiveness of inventory management, including carrying costs, stock-out costs, and wastage costs), and (d) patient care impact (the effect of inventory management on patient health outcomes, satisfaction, and out-of-pocket expenditures). Positive outcomes include high availability, low wastage, good financial efficiency, and positive patient impact. Negative outcomes include stock-outs, high wastage, financial losses, and patient harm (WHO, 2019; Eze and Nwafor, 2020).

The conceptual framework posits that inventory management practices, mediated by inventory control systems, influence inventory management outcomes. Specifically, good procurement practices (accurate quantification, timely ordering) lead to appropriate stock levels. Good storage practices (temperature control, security) reduce spoilage and theft. Good tracking practices (accurate records) enable timely reordering and detection of discrepancies. However, these practices are only effective if supported by appropriate control systems. Manual systems may be adequate for small facilities with low transaction volumes, but larger facilities may require computerized systems. The framework hypothesizes that facilities with better management practices and control systems will have better outcomes (higher availability, lower wastage) (MSH, 2020; WHO, 2019).

An important feature of this conceptual framework is the recognition of moderating variables that influence the relationship between practices, controls, and outcomes. These include: (a) facility level (primary, secondary, tertiary—larger facilities may have more complex inventory needs), (b) staff competence (training and experience of pharmacy staff and storekeepers), (c) infrastructure quality (storage space, refrigeration, electricity, security), (d) funding availability (budget for drug procurement and inventory systems), (e) supply chain reliability (dependability of suppliers and logistics systems), (f) management commitment (priority given to inventory management by facility leadership), (g) regulatory environment (oversight by ministries of health, NAFDAC, PCN), and (h) external support (donor programs, technical assistance). For government health institutions, these moderating variables often determine whether good practices and control systems are actually implemented and effective (Okafor and Udeh, 2020; Adebayo and Oyedokun, 2019).

The framework also recognizes the dynamic and cyclical nature of inventory management. Inventory management is not a one-time event but a continuous cycle of planning, procurement, storage, tracking, dispensing, and monitoring. Feedback from outcomes (e.g., stock-outs, expiries) should inform improvements in practices and controls. For example, recurring stock-outs of a particular drug should trigger a review of procurement practices (e.g., reorder levels, order quantities) and control systems (e.g., monitoring of consumption patterns). The framework therefore includes feedback loops from outcomes back to practices and controls (WHO, 2019; MSH, 2020).

The framework also distinguishes between different types of drugs and their specific management requirements. For example, vaccines require cold chain management; controlled substances (narcotics, psychotropics) require special security and documentation; expensive drugs (e.g., cancer medications) require tighter controls; fast-moving drugs (e.g., antibiotics, analgesics) require more frequent reordering. The framework suggests that inventory management systems should be differentiated by drug type. For government health institutions, this differentiation is often not implemented due to lack of resources or training, leading to uniform (and suboptimal) management of all drugs (WHO, 2019).

Methodologically, the conceptual framework guides the development of research instruments and analytical procedures. Interview guides and survey questionnaires are structured to capture each dimension of management practices (procurement, receiving, storage, tracking, dispensing, disposal), each type of control system (manual, computerized, security, counting, FEFO/FIFO), and each outcome dimension (availability, wastage, financial efficiency, patient impact). Questions probe specific examples from government health institutions. The framework also guides the review of documents, including stock records, procurement documents, inventory reports, and audit findings (Creswell and Creswell, 2018; Saunders, Lewis, and Thornhill, 2019).

Empirical studies that have employed similar conceptual frameworks in health supply chain contexts provide validation for this approach. For example, studies on pharmaceutical inventory management in sub-Saharan Africa found that storage practices (temperature control) and tracking systems (electronic stock cards) were the strongest predictors of drug availability and wastage. Studies in Nigeria found that facilities with trained pharmacy staff and regular inventory audits had significantly lower expiration rates and higher stock availability than those without. In government health institutions specifically, research has found that procurement delays (a practice dimension) and lack of computerized systems (a control dimension) are the top two causes of stock-outs (Adebayo and Oyedokun, 2019; Eze and Nwafor, 2021; Okafor and Udeh, 2020).

The conceptual framework also addresses the unique characteristics of government health institutions in Nigeria. These institutions face specific challenges including unreliable electricity (affecting cold chain), underfunding (affecting procurement and systems), staff shortages (affecting all dimensions), and bureaucratic procurement processes (affecting timeliness). The framework includes these location-specific factors as moderating variables that affect the relationships between practices, controls, and outcomes (Nwankwo and Okeke, 2020; Etim and Bassey, 2020).

Visually, the conceptual framework for this study can be represented as a diagram with “Inventory Management Practices” (independent variable) at the left, with six boxes (procurement, receiving, storage, tracking, dispensing, disposal). An arrow points to “Inventory Control Systems” (mediating variable) in the middle, with five boxes (manual, computerized, security, counting, FEFO/FIFO). A second arrow points from “Inventory Control Systems” to “Inventory Management Outcomes” (dependent variable) on the right, with four boxes (drug availability, drug wastage, financial efficiency, patient impact). Above the diagram are placed the moderating variables (facility level, staff competence, infrastructure, funding, supply chain reliability, management commitment, regulatory environment, external support). Feedback arrows from “Outcomes” back to “Practices” and “Controls” indicate the learning and improvement cycle. This visual representation aids readers in quickly grasping the hypothesized relationships (Miles et al., 2020).

In summary, the conceptual framework of this study provides a clear, logical, and empirically grounded structure for investigating the management and control of drug inventories in government health institutions. By disaggregating management practices into six dimensions, control systems into five types, and outcomes into four dimensions, and by acknowledging the mediating role of control systems, the moderating variables, and the feedback loops, the framework enhances the validity and reliability of the research findings. It also serves as a bridge between the theoretical foundations (discussed in section 2.2) and the empirical investigation (chapters three and four) (Creswell and Creswell, 2018).

2.2 Theoretical Framework

A theoretical framework is a collection of interrelated concepts, definitions, and propositions that present a systematic view of phenomena by specifying relationships among variables, with the purpose of explaining and predicting those phenomena. In this study, five major theories are adopted to explain the management and control of drug inventories in government health institutions: the Theory of Constraints (TOC), the Just-in-Time (JIT) Theory, the Agency Theory, the Public Financial Management (PFM) Theory, and the Systems Theory. These theories collectively provide a robust lens for understanding why inventory management problems arise, how they can be addressed, and what factors influence effectiveness (Goldratt, 1984; Ohno, 1988; Jensen and Meckling, 1976; Premchand, 2019; Von Bertalanffy, 1968).

2.2.1 Theory of Constraints (TOC)

The Theory of Constraints (TOC), developed by Eliyahu Goldratt (1984) as part of the “Theory of Constraints” management philosophy, posits that every system has at least one constraint (bottleneck) that limits its performance. To improve the system, one must identify the constraint, decide how to exploit it, subordinate everything else to that decision, elevate the constraint (increase its capacity), and then repeat the process for the next constraint. In the context of inventory management, TOC suggests that the performance of drug inventory systems is limited by the weakest link in the chain. Improving non-constraints without addressing the constraint will not improve overall performance (Goldratt, 1984; Goldratt and Cox, 2016).

In the context of this study, TOC explains why many government health institutions struggle with drug inventory management despite efforts to improve individual components. For example, a facility may have excellent storage facilities (good infrastructure) but still experience stock-outs because procurement is slow (the constraint). Another facility may have accurate record-keeping (good tracking) but still experience drug expiration because staff are not using FEFO (the constraint). TOC predicts that inventory management will remain poor until the binding constraint is identified and addressed. For government health institutions, common constraints include: funding (inadequate budget for drug procurement), staff (shortage of trained pharmacy personnel), infrastructure (lack of cold chain equipment), and procurement processes (bureaucratic delays). Once the primary constraint is identified, resources should be focused on alleviating it (MSH, 2020; WHO, 2019).

TOC also has implications for inventory control. The theory distinguishes between “throughput” (the rate at which drugs are dispensed to patients), “inventory” (drugs stored), and “operating expense” (costs of running the inventory system). The goal is to increase throughput while reducing inventory and operating expense. This may seem counterintuitive (reducing inventory could lead to stock-outs), but TOC argues that holding excess inventory hides inefficiencies and ties up capital. By identifying and eliminating constraints, facilities can reduce inventory levels without increasing stock-outs. For government health institutions, this means moving away from the practice of “just in case” overstocking (which leads to expiration) toward more precise inventory management (Goldratt and Cox, 2016; Okafor and Udeh, 2020).

Empirical applications of TOC in healthcare supply chains have demonstrated significant improvements. Hospitals that applied TOC reduced inventory levels by 30-50% while improving stock availability. In Nigeria, pilot projects using TOC principles in government health institutions have shown reductions in expiration rates and stock-out days. For the management and control of drug inventories, TOC suggests that a systematic, constraint-focused approach is more effective than piecemeal improvements (Adebayo and Oyedokun, 2019; Eze and Nwafor, 2020).

2.2.2 Just-in-Time (JIT) Theory

Just-in-Time (JIT) Theory, developed by Taiichi Ohno (1988) as part of the Toyota Production System, is an inventory management approach that aims to produce or procure goods only when needed, in the exact quantity needed, thereby minimizing inventory holding costs, reducing waste, and improving efficiency. JIT is characterized by small batch sizes, frequent deliveries, close supplier relationships, and a focus on eliminating waste (including excess inventory, waiting time, defects, and overprocessing). In manufacturing, JIT has been highly successful. In healthcare, JIT principles have been applied to drug inventory management, but with caution because drug shortages can have life-threatening consequences (Ohno, 1988; Liker, 2004).

In the context of this study, JIT Theory explains the potential benefits and risks of minimizing drug inventory levels in government health institutions. The benefits of JIT for drug inventory include: reduced capital tied up in inventory, reduced risk of expiration (since drugs spend less time in storage), reduced storage space requirements, and increased focus on supplier reliability. However, the risks include: stock-outs if suppliers are late or unreliable, inability to respond to sudden demand surges (e.g., disease outbreaks), and increased transaction costs (more frequent ordering). In Nigeria, where supply chains are often unreliable, a pure JIT approach is likely too risky. A modified “JIT with safety stock” approach may be more appropriate (MSH, 2020; WHO, 2019).

JIT Theory also emphasizes the importance of supplier relationships. For JIT to work, suppliers must be reliable, responsive, and close by. In government health institutions, suppliers are often selected through competitive bidding, and contracts may be awarded to the lowest bidder regardless of reliability. Multi-year contracts with performance clauses could encourage supplier reliability. The theory suggests that improving inventory management requires not only changes within the health institution but also changes in procurement practices and supplier management (Okafor and Udeh, 2021; Eze and Nwafor, 2021).

Empirical studies of JIT in healthcare supply chains have found that JIT works best for high-volume, low-cost, non-critical items (e.g., bandages, gloves). For critical, life-saving drugs (e.g., emergency medications), a JIT approach is too risky, and higher safety stocks are justified. For government health institutions, the theory suggests that inventory management strategies should be differentiated by drug criticality and consumption volume (WHO, 2019; MSH, 2020).

2.2.3 Agency Theory

Agency Theory, developed by Jensen and Meckling (1976), describes the relationship between principals (those who delegate authority) and agents (those who act on behalf of principals). In the context of government health institutions, the principals are citizens (taxpayers) and their elected representatives (legislators, ministry officials). The agents are the managers, pharmacists, and other staff who are responsible for managing drug inventories. Agency Theory posits that agents may not always act in the best interests of principals due to information asymmetry (agents have more information about inventory levels, drug usage, and wastage than principals do) and divergent interests (agents may pursue personal goals such as theft of drugs for resale, or shirking of responsibilities) (Jensen and Meckling, 1976; Premchand, 2019).

In the context of this study, Agency Theory explains the problems of drug theft, diversion, and mismanagement in government health institutions. When inventory controls are weak, agents have the opportunity to steal drugs without detection (information asymmetry). When consequences for theft are weak (no prosecution, no termination), agents have the incentive to steal (divergent interests). The theory predicts that strengthening inventory controls (e.g., independent audits, surprise counts, surveillance) reduces information asymmetry and deters theft. It also predicts that stronger enforcement (sanctions for theft) reduces the incentive for theft. For government health institutions, Agency Theory suggests that inventory management problems are not just technical but also behavioral, requiring both control systems and accountability mechanisms (Adebayo and Oyedokun, 2019; Okafor and Udeh, 2020).

Agency Theory also explains the problem of “moral hazard” in inventory management. Agents may take less care in managing inventory (e.g., not rotating stock, not monitoring expiration dates) if they know that shortages or wastage will be blamed on “inadequate funding” rather than on their own actions. The theory suggests that aligning incentives (e.g., linking performance evaluations or bonuses to inventory metrics) can reduce moral hazard. For government health institutions, where salaries are often low and performance incentives rare, Agency Theory suggests that addressing this motivation problem is essential (Nwankwo and Okeke, 2020).

Empirical research has found that stronger inventory controls and accountability mechanisms are associated with lower drug theft and wastage in government health facilities. In Nigeria, facilities that implemented independent inventory audits and staff performance monitoring had significantly lower drug losses. For the management and control of drug inventories, Agency Theory highlights the importance of not only systems but also incentives and oversight (Eze and Nwafor, 2019).

2.2.4 Public Financial Management (PFM) Theory

Public Financial Management (PFM) Theory, as synthesized by Premchand (2019) and others, provides a framework for understanding how public funds are budgeted, spent, accounted for, and audited in government organizations. PFM Theory emphasizes the importance of budget credibility (actual spending aligning with budget allocations), expenditure control (ensuring funds are spent as intended), cash management (ensuring funds are available when needed), accounting and reporting (providing accurate, timely information), and oversight and audit (ensuring accountability). In the context of drug inventory management, PFM Theory explains the financial dimensions of procurement, inventory valuation, and wastage (Premchand, 2019; Chan, 2018).

In the context of this study, PFM Theory explains why government health institutions often face procurement delays and funding shortages that lead to stock-outs. Budgets may be released late, funds may be insufficient (budget credibility problem), or procurement processes may be cumbersome (expenditure control problem). Even when funds are available, cash management problems (e.g., treasury cash not available) can prevent timely drug purchase. The theory suggests that improving drug inventory management requires improving the broader PFM system, not just facility-level practices. For government health institutions, this means advocating for timely budget releases, streamlined procurement, and delegated financial authority (Okafor and Udeh, 2021; Adebayo and Oyedokun, 2020).

PFM Theory also explains the problem of drug expiration and wastage from a financial perspective. Expired drugs represent a loss of public funds; the cost of expired drugs should be tracked and reported. The theory suggests that the cost of wastage should be reported in financial statements and used to evaluate the performance of inventory managers. For government health institutions, making the financial consequences of poor inventory management visible can create accountability and pressure for improvement (Premchand, 2019; Ogbeifun, 2019).

Empirical studies have found that PFM weaknesses (late budget releases, procurement delays) are major causes of drug stock-outs in Nigerian government health institutions. Facilities with more predictable funding and delegated procurement authority have significantly better drug availability. For the management and control of drug inventories, PFM Theory suggests that facility-level improvements must be accompanied by reforms at the ministry and treasury levels (Nwankwo and Okeke, 2020; Etim and Bassey, 2020).

2.2.5 Systems Theory

Systems Theory, developed by Ludwig von Bertalanffy (1968) and others, views an organization as a set of interconnected and interdependent components that work together to achieve a common purpose. A system is more than the sum of its parts; changes in one component affect other components. Systems Theory emphasizes feedback loops, boundaries, inputs, processes, outputs, and the environment. In the context of inventory management, Systems Theory explains why drug availability depends not only on the pharmacy department but also on procurement, storage, distribution, prescribing practices, patient demand, and external factors like supplier reliability and disease outbreaks (Von Bertalanffy, 1968; Senge, 2006).

In the context of this study, Systems Theory explains why piecemeal interventions often fail to improve drug inventory management in government health institutions. Improving storage practices without improving procurement will not solve stock-outs. Improving inventory tracking without improving prescribing practices (which affect consumption) will not optimize inventory levels. The theory suggests that inventory management must be viewed as a system, and interventions must address multiple components simultaneously. For government health institutions, this means that improving drug inventory management requires coordination across departments (pharmacy, administration, finance, clinical services) and levels (facility, local government, state, federal) (WHO, 2019; MSH, 2020).

Systems Theory also emphasizes the importance of feedback loops. In a well-functioning system, information about stock-outs and expirations flows back to procurement and planning, triggering corrective action. In many government health institutions, feedback loops are weak or broken. Data on consumption is not used to adjust order quantities. Information on expired drugs is not used to modify storage practices. The theory suggests that strengthening feedback loops (e.g., through regular inventory reviews, performance dashboards, and cross-departmental meetings) can improve system performance (Senge, 2006; Okafor and Udeh, 2021).

Empirical studies have found that health supply chain interventions that take a systems approach (addressing procurement, storage, distribution, and tracking together) are more effective than interventions addressing single components. In Nigeria, projects that implemented integrated supply chain reforms (including training, infrastructure, and information systems) achieved sustained improvements in drug availability. For the management and control of drug inventories, Systems Theory suggests the need for a holistic, multi-component intervention strategy (Eze and Nwafor, 2021; Adebayo and Oyedokun, 2019).

2.2.6 Synthesis of the Five Theories

Taken together, the Theory of Constraints (TOC), Just-in-Time (JIT) Theory, Agency Theory, Public Financial Management (PFM) Theory, and Systems Theory provide a comprehensive, multi-layered theoretical foundation for this study. TOC explains that performance is limited by constraints; improving non-constraints is ineffective until the constraint is addressed. JIT Theory explains the potential benefits and risks of minimizing inventory levels, suggesting differentiation by drug criticality. Agency Theory explains behavioral problems (theft, shirking, moral hazard) and the need for controls and accountability. PFM Theory explains the financial and budgetary dimensions of drug inventory management, including procurement delays and funding shortages. Systems Theory explains the interconnections between components and the need for a holistic approach (Goldratt, 1984; Ohno, 1988; Jensen and Meckling, 1976; Premchand, 2019; Von Bertalanffy, 1968).

The synthesis of these theories also guides empirical testing and practical recommendations. Research questions and hypotheses derived from this theoretical framework can focus on: from TOC, the identification of binding constraints at government health institutions; from JIT, the feasibility and risks of reducing safety stock levels; from Agency Theory, the effectiveness of controls in reducing theft and wastage; from PFM Theory, the impact of budget delays and procurement processes on stock availability; and from Systems Theory, the interconnections between different inventory management components. The framework suggests that improving drug inventory management in government health institutions requires: identifying and addressing binding constraints (TOC), balancing inventory reduction with stock-out risk (JIT), strengthening controls and accountability (Agency), reforming procurement and budget processes (PFM), and taking a holistic, system-wide approach (Systems) (Creswell and Creswell, 2018).

In conclusion, the theoretical framework of this study is firmly anchored in five well-established, complementary theories: Theory of Constraints (Goldratt, 1984), Just-in-Time Theory (Ohno, 1988), Agency Theory (Jensen and Meckling, 1976), Public Financial Management Theory (Premchand, 2019), and Systems Theory (Von Bertalanffy, 1968). These theories collectively explain the management and control of drug inventories in government health institutions, the factors that influence effectiveness, the behavioral challenges, the financial and budgetary dimensions, and the need for a systems approach. The framework provides a solid foundation for the conceptual framework (section 2.1), the research methodology (chapter three), and the interpretation of findings (chapters four and five) (Miles et al., 2020).