How to Accurately Estimate, Order, and Stock Drugs

Running out of essential medications during a health emergency or finding expired drugs piling up in storage-both scenarios can be dangerous and costly. For nurses and healthcare professionals working in clinical settings, understanding how to estimate, order, and stock drugs efficiently is a fundamental skill. It ensures patients receive the right medications at the right time while minimizing wastage and financial losses.

Why accurate drug estimation matters 🔗

Drug estimation forms the backbone of any effective pharmaceutical supply system. According to the World Health Organization, essential medicines should be available, affordable, and of assured quality at all times. When estimation is done poorly, healthcare facilities face either stockouts-where critical medications become unavailable-or overstocking, which leads to drugs expiring before use.

The consequences of poor estimation extend beyond finances. Patients may receive substandard treatment or no treatment at all when life-saving drugs are unavailable. On the other hand, expired medications represent wasted resources that could have been used elsewhere. A systematic approach to drug requirement estimation helps prevent these problems and ensures the smooth functioning of healthcare services.

How to calculate drug requirements 🔗

The estimation process involves a straightforward calculation: multiply the total dose needed for an average treatment course by the number of patients expected to be treated within your purchasing interval. This method, known as morbidity-based estimation, uses disease patterns and treatment protocols to predict drug needs.

Understanding the calculation formula 🔗

To estimate requirements for any medication, you need three pieces of information: the standard treatment dose, the duration of treatment, and the expected number of patients. For instance, if treating 100 patients with a condition requiring 500 mg of a drug twice daily for 7 days, the total requirement would be 100 patients × 500 mg × 2 doses × 7 days = 700,000 mg or 700 grams of that medication.

Médecins Sans Frontières recommends calculating average monthly consumption (AMC) from outgoing stock records by adding the quantities dispensed over several months and dividing by the number of months considered. This consumption data becomes the foundation for future orders.

Factors affecting drug requirements 🔗

Several variables influence how much of each drug a facility needs. Seasonal disease patterns can significantly impact requirements-flu season increases demand for antivirals and antibiotics, while summer may see higher usage of allergy medications. Changes in patient volume, new treatment protocols, and disease outbreaks all affect consumption patterns. Regular evaluation of needs and consumption helps verify whether prescription schemes are being followed correctly and prevents potential stock shortages.

Ordering drugs effectively 🔗

Once you have estimated your requirements, the ordering process requires careful consideration of several factors to maximize value and ensure timely delivery.

Choosing generic over brand-name drugs 🔗

Ordering generic (non-brand-name) drugs instead of branded equivalents can substantially reduce costs without compromising quality. The WHO Model List of Essential Medicines, which guides national drug policies in over 150 countries, designates medications by their International Nonproprietary Name (INN) rather than brand names. Using the INN in orders and prescriptions avoids confusion since the same drug may be sold under multiple brand names by different manufacturers.

Specifying quantities and dosage forms 🔗

Orders should clearly specify the exact quantities needed, dosage forms (tablets, capsules, injections, suspensions), and strength of each medication. Avoiding multiple strengths or forms of the same drug simplifies management-in most cases, one adult formulation and one pediatric formulation are sufficient.

Making cost estimates 🔗

Before placing orders, prepare cost estimates to ensure your budget can accommodate the required quantities. This involves checking current prices from suppliers and wholesalers, accounting for shipping costs, and building in a contingency for price fluctuations. Some facilities maintain relationships with multiple suppliers to compare prices and ensure supply continuity if one source faces shortages.

Calculating order quantities 🔗

The MSF pharmaceutical management guidelines outline a formula for determining order quantities: Order = (running stock + buffer stock + probable consumption during delivery delay) – (inventory + orders not yet delivered). Running stock represents consumption between deliveries, while buffer stock compensates for possible delays or unexpected increases in consumption.

Stocking drugs properly 🔗

Proper storage ensures medications remain effective until their expiry date. Poor storage conditions can cause drugs to deteriorate, reducing their therapeutic value or making them potentially harmful.

Maintaining stock records 🔗

A stock ledger or card system is the primary instrument for stock control. A bin card is maintained for each item in stock, recording quantities received, quantities issued, and the current balance after each transaction. This system enables quick identification of stock levels and helps prevent both shortages and overstocking.

Stock cards should include the drug name (INN), form and strength, all movements (incoming, outgoing, origin, destination), dates, expiry dates, and inventory counts. Recording quantities in units (tablets, ampoules) rather than boxes ensures accuracy. Each transaction should be entered on a separate line, even if multiple transactions occur on the same day.

Storage conditions 🔗

Drug stability depends on environmental factors including temperature, humidity, and light exposure. Most medications should be stored in cool, dry conditions away from direct sunlight. The storage area should have good ventilation, and temperatures ideally should not exceed 25°C. A ceiling underneath the roof helps reduce ambient temperature, and windows should be shaded.

Protection from dampness is critical-humidity can cause tablets to deteriorate, labels to peel, and packaging to degrade. Products should never be stored directly on the floor but on pallets that allow air circulation. Refrigerated medications require constant temperature monitoring between 2-8°C, with backup systems in place for power failures.

Light protection is equally important. Drugs should not be exposed to direct sunlight during storage as this can impair their effectiveness. Original packaging often provides some protection, but medications should still be stored in north-facing rooms or areas not affected by direct sunlight.

Marking expiry dates and FIFO principle 🔗

Healthcare facilities should follow the FIFO (First In, First Out) or FEFO (First Expired, First Out) principle to prevent medications from expiring on shelves. Products with the earliest expiry dates should be placed at the front and dispensed first, while newer stock with longer shelf life goes behind.

Clearly marking expiry dates on all packages with a large marker makes it easy to identify which items need to be used first. Some facilities use color-coded stickers to highlight short-dated products. This systematic approach ensures older stock is used before newer arrivals and minimizes losses from expired medications.

Monitoring stock levels 🔗

Regular monitoring of stock levels, particularly for life-saving drugs, ensures their constant availability and helps identify discrepancies in drug usage. Physical inventory counts should be conducted before each order and compared against theoretical stock levels shown on cards.

Setting minimum and maximum levels 🔗

Each medication should have established minimum (buffer) and maximum stock levels. The minimum level triggers a reorder, while the maximum prevents over-purchasing. Buffer stock quantities are typically calculated as half the consumption during the period between deliveries, though this may vary based on delivery reliability and consumption variability.

Identifying discrepancies 🔗

Differences between physical stock counts and recorded balances may indicate recording errors, theft, or waste. These discrepancies should be investigated and clarified promptly. Regular audits help maintain accuracy and accountability in the pharmaceutical supply system.

Ensuring quality through proper management 🔗

Good pharmaceutical management extends beyond numbers and storage conditions. The NCBI notes that ensuring needed essential medicines are available is critical for any disease control program. Careful selection, procurement from reliable suppliers, proper storage and distribution, and rational use are all interconnected components of an effective drug supply system.

Security of stocks requires solid doors and locks, with controlled access to storage areas. Controlled substances like narcotics require additional safeguards including locked storage and separate registers documenting all movements. Only authorized personnel should have access to the pharmacy, and the person in charge should maintain sole possession of keys.

What do you think? How does your healthcare facility currently manage drug estimation and stock control? What challenges have you encountered in maintaining adequate supplies of essential medications while avoiding wastage?

References

1. https://www.who.int/news-room/fact-sheets/detail/essential-medicines
2. https://medicalguidelines.msf.org/en/viewport/EssDr/english/organization-and-management-of-a-pharmacy-16688159.html
3. https://www.who.int/groups/expert-committee-on-selection-and-use-of-essential-medicines/essential-medicines-lists
4. https://ceopedia.org/index.php/Bin_card
5. https://medicalguidelines.msf.org/en/viewport/EssDr/english/drug-quality-and-storage-16688167.html
6. https://www.swisslog-healthcare.com/en-gb/products/pharmacy-automation/boxpicker/storage-of-medicines-in-hospitals
7. https://medcitynews.com/2020/10/7-best-practices-for-pharmacies-managing-short-dated-inventory/
8. https://www.ncbi.nlm.nih.gov/books/NBK11723/