<p>Cannabinoids, barbiturates, opiates, and alcohol may have additive effects with Trihexyphenidyl, and thus, an abuse potential exists. Concurrent use of alcohol or other CNS depressants with Trihexyphenidyl may cause increased sedative effects. It may be contraindicated in patients taking monoamine oxidase inhibitors &amp; tricycllic antidepressants.</p>