Rationale for rate-controlled drug delivery of cardiovascular drugs by the transdermal route.

If the therapeutic effects of a drug are to be maximized and maintained while the side effects are minimized, an optimal concentration of drug in blood plasma must be sustained continuously. Conventional dosage forms such as tablets, capsules, or elixirs describe a peak-and-valley curve when their dosage intervals are charted, demonstrating great fluctuations in the safety and effectiveness of a drug during the dosage interval. The need for certain drugs to be delivered at a constant, or zero-order, rate has led to the development of rate-controlled drug delivery systems, which by definition deliver drug in precise quantities over time. One such system uses the transdermal route, which is discussed here in terms of convenience, compliance, reliability, and potential as a vehicle for cardiovascular agents.