A drug-in-adhesive transdermal patch for S-amlodipine free base: in vitro and in vivo characterization.

The objective of the present investigation was to develop and evaluate a drug-in-adhesive transdermal patch for S-amlodipine (S-AM) free base. Initial in vitro experiments were conducted to optimize the formulation parameters before transdermal delivery in rats. The effects of the type of adhesive and the content of permeation enhancers on S-AM free base transport across excised rat skin were evaluated. For in vivo studies, patches were administered transdermally to rats while orally administered S-AM in suspension and intravenously administered S-AM solution were used as controls. The plasma level of S-AM following transdermal application could be maintained for 72 h. After transdermal administration to rats, the absolute bioavailability was 88.8% for S-AM free base. After dose normalization, the areas under the plasma concentration-time curve (AUC) and mean residence times (MRT) were evidently increased and extended, respectively. This suggests that the transdermal application of S-AM in a drug-in-adhesive transdermal patch may be used for the treatment for hypertension.