Trihexyphenidyl may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
drowsiness
dizziness or blurred vision
dry mouth
upset stomach
vomiting
diarrhea
constipation
increased eye sensitivity to light
difficulty urinating
If you experience any of the following symptoms, call your doctor immediately:
skin rash
fast, irregular, or pounding heartbeat
fever
confusion
depression
delusions or hallucinations
eye pain