Trihexyphenidyl is an antimuscarinic medication used to treat Parkinson's disease and extrapyramidal symptoms. Learn about its uses, side effects, precautions, and how to store and dispose of it. Trihexyphenidyl is a prescription drug for Parkinson's Disease and Drug-induced Extrapyramidal Symptoms. It has antiparkinson and anticholinergic effects, but also many side effects and interactions. Learn more about its uses, dosages, side effects, and warnings. Trihexyphenidyl oral tablet is a prescription medication used to treat all forms of parkinsonism, including Parkinson’s disease. It’s also used to treat severe movement side effects caused by ... Trihexy 2mg Tablet is also used to treat side effects like abnormal movements caused by antipsychotic drugs. It helps restore normal body posture as well as control over muscle movements in the body. This will enable you to lead a normal life and improve your ability to carry out daily activities.