What side effects may I notice from receiving Trihexyphenidyl?

Side effects that you should report to your doctor or health care professional as soon as possible:
-allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
-changes in vision
-fast or irregular heartbeat
-hallucinations
-vomiting

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):
-anxiety or nervousness
-dizziness
-drowsiness
-nausea

This list may not describe all possible side effects for Trihexyphenidyl. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.