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trihexyphenidyl (trye-heks-ee-fen-i-dil)

Apo-Trihex, Artane,

PMS-Trihexyphenidyl, Trihexane, Trihexy


Therapeutic: antiparkinson agents

Pharmacologic: anticholinergics


Adjunct in the management of parkinsonian syndrome of many causes, including drug-induced parkinsonism.


Inhibits the action of acetylcholine, resulting in Decreased sweating and salivation, Mydriasis (pupillary dilation), Increased heart rate. Also has spasmolytic action on smooth muscle. Inhibits cerebral motor centers and blocks efferent impulses. Therapeutic Effects: Diminished signs and symptoms of parkinsonian syndrome (tremors, rigidity).

Adverse Reactions/Side Effects

CNS: dizziness, nervousness, confusion, drowsiness, headache, psychoses, weakness. EENT: blurred vision, mydriasis. CV: orthostatic hypotension, tachycardia. GI: dry mouth, nausea, constipation, vomiting. GU: urinary hesitancy, urinary retention. Derm: decreased sweating.


Examination and Evaluation

  • Assess patient's gait and motor function to help document antiparkinson effects, especially when starting drug therapy or during dosing changes or addition of other antiparkinson drugs. Motor function should be assessed at different times of the day, such as when drugs are reaching therapeutic levels (i.e., 2–3 hr after oral dose), as well as when drug effects are minimal (just before the next dose).

  • Assess heart rate, ECG, and heart sounds, especially during exercise (See Appendices G, H). Report fast heart rate (tachycardia) or signs of other arrhythmias, including palpitations, chest discomfort, shortness of breath, fainting, and fatigue/weakness.

  • Assess blood pressure (BP) when patient assumes a more upright position (lying to standing, sitting to standing, lying to sitting). Document orthostatic hypotension and contact the physician when systolic BP falls >20 mm Hg, or diastolic BP falls >10 mm Hg.

  • Report confusion, nervousness, psychosis, and other psychologic problems. Repeated or excessive symptoms may require change in dose or medication.

  • Assess dizziness and drowsiness that might affect gait, balance, and other functional activities (See Appendix C). Report balance problems and functional limitations to the physician, and caution the patient and family/caregivers to guard against falls and trauma.


  • Implement therapeutic exercises (coordination exercises, gait training, cardiovascular conditioning) to complement the effects of drug therapy and help achieve optimal function.

  • Because of the risk of arrhythmias and abnormal BP responses, use caution during aerobic exercise and other forms of therapeutic exercise. Assess exercise tolerance frequently (BP, heart rate, fatigue levels), and terminate exercise immediately if any untoward responses occur (See Appendix L).

  • Guard against falls and trauma (hip fractures, head injury, and so forth). Implement fall- prevention strategies (See Appendix E), especially if patient exhibits Parkinson's symptoms (postural instability, rigidity) combined with drug side effects (dizziness, blurred vision, weakness).

  • To minimize orthostatic hypotension, patient should move slowly when assuming a more upright position.

Patient/Client-Related Instruction

  • Instruct patient ...

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