WHO Essential Medicines List: Core Medications for Healthcare Systems
The WHO Essential Medicines List (EML) defines the minimum medicines necessary for a functioning healthcare system, currently including over 300 medications selected based on cost-effectiveness, safety, ready availability, and evidence-based efficacy for priority health conditions. 1
Definition and Core Purpose
The WHO Model List of Essential Medicines represents medications deemed necessary for a basic healthcare system to function effectively, addressing the most important healthcare needs of populations through cost-effective, safe, and readily available medications. 1 This concept, first introduced in 1977 with 186 drugs, has evolved into a comprehensive list exceeding 300 medications that is updated biennially. 2, 3
Major Categories of Essential Medicines
Antibiotics: The AWaRe Classification System
The 2023 AWaRe classification provides the most current framework for essential antibiotics, organizing 41 antibiotics across three strategic groups for over 30 clinical infections. 1
Access Group (First-Line Antibiotics):
- Includes narrow-spectrum antibiotics recommended as empiric first- or second-choice treatment for common clinical infections 4
- Core agents include amoxicillin-clavulanic acid, cloxacillin/dicloxacillin, cefalexin, clindamycin, and metronidazole 1
- These should be widely available in appropriate formulations, affordable, and of assured quality 4
Watch Group (Second-Line Antibiotics):
- Contains broader-spectrum antibiotics with greater resistance concerns and toxicity potential 4
- Key medications include ceftriaxone, piperacillin-tazobactam, vancomycin, levofloxacin, and ciprofloxacin 1
- These are targets for antimicrobial stewardship programs and include the highest priority agents on the List of Critically Important Antimicrobials 4
Reserve Group (Last-Resort Options):
- Reserved for highly specific patient populations with severe or life-threatening infections due to multidrug-resistant bacteria 4
- Includes carbapenems and polymyxins 1
- Should only be used when other alternatives have failed or would be inadequate 4
Cancer Therapeutics
The 22nd WHO EML expanded to include targeted and immune-modulating therapies for various cancers, including trastuzumab, imatinib, erlotinib, gefitinib, afatinib, nivolumab, and pembrolizumab. 1 This represents a significant evolution from the original concept, now incorporating high-priced medicines when they meet essential criteria. 3
Pain Management Medications
Non-Opioid Analgesics (WHO Level I):
- Acetaminophen (paracetamol): 500-1000 mg, maximum 4-6 grams daily 4
- Acetylsalicylic acid: 500-1000 mg, maximum 3 grams daily 4
- Ibuprofen: 200-600 mg, maximum 2400 mg daily 4
- Diclofenac, ketoprofen, naproxen for specific indications 4
Opioid Analgesics (WHO Level III):
- Morphine sulfate (oral and parenteral formulations) 4
- Oxycodone, hydromorphone, fentanyl (transdermal), buprenorphine, and methadone 4
Implementation Principles
Availability Requirements: Essential medicines must be available at all times to everyone within a functioning healthcare system, satisfying priority healthcare needs of populations. 1
National Adaptation: National essential medicines lists should be country-specific, considering local disease prevalence and antimicrobial resistance patterns, ensuring therapeutic choices are consistent and cost-effective, and enabling national pricing negotiations for generic medicines. 1 National lists include, on average, only 66% of antibiotics from the WHO EML, with many low- and middle-income countries lacking access to carbapenems, glycopeptides, and polymyxins. 4
Global Access Disparities
High-Income Countries: Essential medicines are almost always available at no cost or subsidized, with formulary inclusion rates exceeding 90% for most essential medicines. 1
Low- and Middle-Income Countries: Medicines are generally provided only at full out-of-pocket cost, with generic availability in the public sector ranging from 36.1% to 44.3%. 1 Financial barriers such as high medication costs and supply chain issues including inadequate stock and poor distribution hinder access. 1
Monitoring and Surveillance Requirements
Countries should systematically monitor patterns of antibiotic use, trends in antimicrobial resistance development, and proportions of patients without access to essential antibiotics. 1 The WHO Global Antimicrobial Resistance and Use Surveillance System (GLASS) provides standardized methodology, though only 14% of countries actively report consumption data. 1, 4
Selection Criteria Evolution
The process of defining essential medicines has evolved from experience-based to evidence-based, incorporating criteria such as public-health relevance, efficacy, safety, and cost-effectiveness. 3 The WHO Expert Committee updates the list biennially using the 5-level Anatomical Therapeutic Chemical (ATC) classification system. 5