Pharmacokinetics of nitroglycerin and clonidine delivered by the transdermal route

This article describes in vitro and in vivo performance of two transdermal drug delivery systems. Transderm -Nitro delivers nitroglycerin for the treatment and prevention of angina for 24 hours following a single application. In a three-way crossover study comparing Transderm -Nitro with two other transdermal nitroglycerin products, mean plasma levels of drug were similar 0.5 and 6 hours after application; however, with Transderm -Nitro the area under the plasma concentration curve was highest and the coefficient of variation was least. A transdermal therapeutic system for delivering clonidine ( Catapres -TTS) is used for the treatment of hypertension. In a two-way crossover study comparing Catapres -TTS and oral Catapres , plasma levels of clonidine with use of the transdermal system reached a steady-state value in 2 to 3 days and remained steady for the duration of the wearing period; plasma levels with oral Catapres , however, fluctuated markedly. The ratio of maximum to minimum plasma levels during a dosing interval was 2 for oral Catapres and approximately 1 for Catapres -TTS. The potential use of intact skin as a route of entry for controlled delivery of drugs to the systemic circulation is promising.