METABOLISM OF PROPRANOLOL DURING PERCUTANEOUS-ABSORPTION IN HUMAN SKIN

This in vitro study evaluated the extent of the absorption and metabol ism of propranolol in human skin from four sources. Between 10.4 +/- 3 .1 and 36.6 +/- 2.6% of the applied dose was absorbed; however, only a small portion (between 4.1 +/- 0.9 and 16.1 +/- 1.3%) of the dose per meated through the skin. Naphthoxyacetic acid formed during percutaneo us absorption was located in the skin supernate. 4'-Hydroxypropranol w as formed during percutaneous absorption and by skin microsomes. In ad dition, the microsomes biotransformed propranolol to norpropranolol. T he retention of some of the absorbed drug and metabolites in the skin could explain the low plasma concentration and irritation observed fol lowing topical application of propranolol.