Which of the following antipsychotic medications is an antidepressant available in a transdermal patch?

The antipsychotic medication that is available in a transdermal patch is selegiline. This medication is primarily used in the treatment of Parkinson's disease and major depressive disorder. The transdermal patch formulation allows for continuous absorption of the drug through the skin, which can result in more stable blood levels and can enhance patient compliance compared to oral administration.

Selegiline works as a selective inhibitor of monoamine oxidase B (MAO-B), and at higher doses, it also inhibits monoamine oxidase A (MAO-A), which contributes to its antidepressant effects. This dual mechanism helps increase the availability of neurotransmitters like dopamine and norepinephrine in the brain, thereby alleviating symptoms of depression.

The other options listed are all monoamine oxidase inhibitors as well, but they do not have a transdermal patch formulation available. Tranylcypromine and phenelzine are both oral medications, while quazepam is a benzodiazepine and not classified under antidepressants. Thus, selegiline stands out as the only option that fits the criterion of being an antidepressant available in a transdermal patch.