Delivery of a medicinal product directly to the target organ, for instance, the lung, offers many advantages to the patient but presents special difficulties in assessment of quality and bioequivalence, since conventional measurements are not always appropriate.
This paper reviews, from a regulatory perspective, the standards set for determining the clinical equivalence of inhaled dosage forms, in particular, metered-dose inhalers (MDI), which are used in the management of asthma. This is particularly pertinent given the urgent need to reformulate products which contain chlorofluorocarbon (CFC) propellants.
Generic MDI products have been approved and regulatory standards published in Canada, Australia, and New Zealand. Generic MDI products have been registered in Europe but there are no published standards. The United States Food and Drug Administration (FDA) has spent many years debating these issues and has released many draft and interim guidelines but as yet has not approved any generic MDIs. There is a good opportunity for international harmonization of standards for MDIs with the development and introduction of non-CFC formulations.
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