A composition for transdermal delivery of a progestin for progestin hormone therapy is disclosed. Also disclosed is a transdermal delivery device comprising the composition. For progestin-only hormone therapy, the composition contains an anti-oxidant and does not contain an estrogen. For therapy involving a progestin and an estrogen, the composition contains the progestin, the estrogen and an additional anti-oxidant. Methods of improving the stability of progestin-containing compositions comprising oxidative agents are also disclosed. The methods comprise including one or more anti-oxidants in the compositions.
