Research challenges, new drug development, preclinical and clinical trials in the ageing population.

The aged are now viewed as a special population for the purposes of drug development. This has produced challenges for the investigator, in that separation of age- and disease-related changes in drug effect is only beginning to be defined. In addition, development of measurement tools for use in the elderly, particularly for central nervous system-active drugs, is an important ongoing process. As investigations proceed, we can look forward to an improved understanding of the physiology of normal ageing and the impact of disease processes and drugs on this physiological functioning. For the regulatory agency, evaluation of both efficacy and toxicity data in elderly patients for a drug-in-development is required; however, at present these data will be obtained in a 'young' elderly group, whereas much of the clinical use of the drug will be in the 'old' elderly. Extrapolation from one group to the other is required, although the relevance of this extrapolation is unknown. It is reassuring that, so far, few if any drug effects or toxicities have been identified which are truly unique to the elderly, though the magnitude of pharmacological or toxicological effects may differ.