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close this bookThe Use of Essential Drugs: Eight report of the WHO Expert Committee (WHO - OMS, 1998, 84 p.)
View the document(introduction...)
View the documentWHO Expert Committee on the Use of Essential Drugs - Geneva, 1-5 December 1997
View the document1. Introduction
View the document2. Guidelines for establishing a national programme for essential drugs
View the document3. Criteria for the selection of essential drugs
View the document4. Guidelines for the selection of pharmaceutical dosage forms
Open this folder and view contents5. Quality assurance
Open this folder and view contents6. Reserve anti-infective agents and monitoring of resistance
View the document7. Applications of the essential drugs concept
Open this folder and view contents8. Essential drugs and primary health care
View the document9. Drug donations
View the document10. Post-registration drug studies
Open this folder and view contents11. Research and development
View the document12. Nomenclature
View the document13. Drug information and educational activities
View the document14. Selection and updating of lists of essential drugs
View the document15. Model List of Essential Drugs (tenth list)
View the document16. Considerations and changes made in revising the model list
View the document17. Glossary of terms used in the report
View the documentAcknowledgement
View the documentReferences
View the documentAnnex 1. Application form for inclusion in the Model List of Essential Drugs1
View the documentSelected WHO publications of related interest
View the documentBack Cover

4. Guidelines for the selection of pharmaceutical dosage forms

The purpose of selecting dosage forms and strengths for the drugs in the model list is to provide guidance to countries wishing to standardize or minimize the number of preparations in their own drug lists. As a general rule, pharmaceutical forms are selected on the basis of their general utility and their wide availability internationally. In many instances, a choice of preparations is provided, particularly in relation to solid dosage forms. Tablets are usually less expensive than capsules, but, while cost should be taken into account, the selection should also be based on a consideration of pharmacokinetics, bioavailability, stability under ambient climatic conditions, availability of excipients, and established local preference.

In a few instances where there is no uniformity of tablet strength, for example acetylsalicylic acid and paracetamol, a dosage range is provided from within which suitable tablet strengths should be selected on the basis of local availability and need. When precise dosage is not mandatory, the use of scored tablets is recommended as a simple method of making dosage more flexible if so required and, in some instances, to provide a convenient paediatric dose. Specific paediatric dosages and formulations are included in the list only when indicated by special circumstances. In many instances, dosage is specified in terms of a selected salt or ester, but in others - for example chloroquine - it is calculated, in accordance with common practice, in terms of the active moiety.

For certain drugs with short half-lives that are rapidly metabolized, such as carbamazepine, calcium-channel blockers and theophylline, conventional-release dosage forms must often be taken three or four times a day to maintain drug levels in the required narrow range. Sustained-release dosage forms can reduce the frequency of drug administration, thereby improving compliance and, often, the therapeutic effectiveness of the drug by maintaining a more constant drug level than can be obtained using traditional dosage forms. Because the preparation of sustained-release products is difficult and requires special expertise, a proposal to include such a product in a national list of essential drugs should be justified by adequate documentation.