Transdermal absorption of L-dopa from hydrogel in rats

To improve compliance in administration of L-dopa, transdermal absorption o f the agent was investigated in rats in vitro employing two-chamber diffusi on cells in which the excised rat abdominal skin was mounted, and in vivo u sing an alcoholic hydrogel containing L-menthol. The in vitro study reveale d that in presence of L-menthol (2%, W/W), ethanol (20 and 40%, V/V) accele rated transdermal penetration of L-dopa with an increase of its percentages . The in vivo study showed that when the L-dopa-hydrogel containing 2% L-me nthol and 40% ethanol was attached on the skin, plasma levels of L-dopa and norepinephrine increased with the time elapsed; the level of dopamine incr eased and reached a plateau thereafter; and the level of epinephrine was un changed. These in vitro and in vivo findings indicated that the hydrogel fo rmulation of L-dopa provides new direction in treating Parkinson's disease. (C) 1998 Elsevier Science B.V. All rights reserved.