This course forms a bridge between PHPH9101 (Principles of Drug Action) and PHPH9120 (Clinical Development of Medicines]. The pharmacodynamic and pharmacokinetic principles introduced in PHPH9101 will be extended by a review of the major classes of pharmacological substances including those acting on the central and peripheral nervous systems and the major organ systems such as cardiovascular, pulmonary, renal, etc. Clinical uses and limitations of the drugs will be summarized and examples given showing the application of pharmacodynamic and pharmacokinetic principles to clinical situations. Laboratory and clinical methods will be reviewed to show how drug efficacy and safety are assessed in laboratory and then clinical settings. Systematic safety assessment will then be reviewed. This will cover: (a) aims and definitions of safety assessment programmes; (b) design and execution of toxicological studies; (c) special studies such as carcinogenicity, mutagenicity and reproductive studies; (d) toxicokinetics; and (e) design and interpretation of toxicological studies. The second half of this course covers an introduction to epidemiology and statistics with emphasis of the use of statistical concepts in clinical study design. The various forms of clinical study including observational and experimental will be covered. This provides essential background for the third course in this programme, namely Clinical Development of Medicines (PHPH9120).