In many countries, for reasons of economy, drugs destined for use in the public sector are purchased on open tender. This favours the use of generic products, and the practice in some countries is for tenders to be issued, bids examined, and contracts offered by the procurement authority without reference to the drug regulatory authority.
The licensing of generic products poses a challenge to all regulatory authorities, particularly when the product to be supplied is not registered in the country of origin. The need for expert assessment is accentuated because not all drug-exporting countries submit drugs intended exclusively for export to the same rigorous controls as drugs intended for the domestic market. Nominally equivalent generic products should contain the same amount of the same therapeutically active ingredients in the same dosage form and they should meet required pharmacopoeial standards. However, they are not necessarily identical and in some instances their clinical interchangeability may be in question. Differences in colour, shape and flavour, while obvious and sometimes disconcerting to the patient, are often inconsequential to the performance of the product, but differences in sensitizing potential due to the use of different excipients and differences in stability and bioavailability have obvious clinical implications. Regulatory authorities consequently need to consider not only the quality, efficacy and safety of such products, but also their interchangeability one with another and with the original innovative product. This concept of interchangeability applies not only to the dosage form but also to the instructions for use and even to the packaging specifications, when these are critical to stability and shelf-life.
Some highly evolved authorities require that every generic product must satisfy three sets of criteria of therapeutic equivalence. These relate to:
(a) manufacturing and quality control;
(b) product characteristics and labelling; and
Others adopt a more pragmatic approach to the need for experimental demonstration of bioequivalence. Study of the bioavailability of a dosage form is a costly undertaking that is demanding of human resources. It is clearly not a cost-effective requirement for highly water-soluble substances, when neither precise dosage nor consistency of response is a critical consideration. In developing countries the in vivo bioavailability testing of all domestically manufactured products would be impracticably costly. The regulatory authority should be in a position to help local manufacturers by advising them on drugs that pose potential bioavailability problems.
In the case of imported products, assurance should be obtained through the WHO Certification Scheme on the Quality of Pharmaceutical Products Moving in International Commerce that the product has been produced in accordance with WHO’s standards of good manufacturing practices and that, in the light of a full assessment, it has been authorized to be placed on the market in the country of origin.