Class: Anticholinergic Agents
VA Class: AU350
CAS Number: 52-49-3
Medically reviewed by Drugs.com. Last updated on Sep 21, 2020.
Introduction
Antimuscarinic antiparkinsonian agent.a b
Uses for Trihexyphenidyl
Parkinsonian Syndrome
Adjunctive treatment of all forms of parkinsonian syndrome.a b
May reduce the frequency and duration of oculogyric crises, salivation, spastic contractions, and dyskinesia, and relieve mental inertia and depression characteristic of all forms of parkinsonian syndrome.b
Drug-Induced Extrapyramidal Reactions
Control of extrapyramidal reactions induced by antipsychotic agents (e.g., phenothiazines, thioxanthenes).a b
Trihexyphenidyl Dosage and Administration
Administration
Oral Administration
Administer orally before or after meals, depending on patient reaction.a b Administer before meals in patients with excessive xerostomia.a Administer after meals if nausea occurs.a
May be administered 3 times daily; if a fourth dose is required, administer at bedtime.b
Mint candies, chewing gum, water, or administration of a saliva substitute (e.g., Xero-lube) may relieve xerostomia that may accompany administration after meals.a b
Dosage
Available as trihexyphenidyl hydrochloride; dosage expressed in terms of the salt.a
Adjust dosage carefully according to individual requirements and response.b
Adults
Parkinsonian Syndrome
Oral
Initially, 1 mg on first day.a Dosages may be increased in 2-mg increments at 3- to 5-day intervals up to a maximum of 6–10 mg daily.a b
Postencephalitic patients: 12–15 mg daily may be required.a b
When trihexylphenidyl is used as an adjunct to levodopa, consider reducing levodopa and trihexyphenidyl dosages.a Generally, 3–6 mg daily of trihexyphenidyl hydrochloride is adequate.a
If trihexyphenidyl is replacing another antiparkisonian agent, increase trihexyphenidyl dose as needed while decreasing other drug dose until complete replacement is achieved.b
Drug-Induced Extrapyramidal Reactions
Oral
Usual dosage: 5–15 mg total daily dosage.a b
Initially, 1 mg; if extrapyramidal reactions are not controlled within a few hours, progressively increase dosage until control is achieved. a b
Alternatively, to achieve a more rapid control, reduce dosage of the drug causing the reaction, then adjust the dosage of both drugs to attain the desired drug effect without extrapyramidal symptoms.b Once control of extrapyramidal reactions has been maintained for several days, dosage of trihexyphenidyl may be reduced or discontinued.b
Prescribing Limits
Adults
Parkinsonian Syndrome
Oral
Maximum of 6–10 mg daily in most patients; postencephalitic patients may require 12–15 mg daily.a b
Special Populations
Hepatic Impairment
No specific dosage recommendations at this time.a
Renal Impairment
No specific dosage recommendations at this time.a
Geriatric Patients
Patients ≥60 years of age: Initiate with low dosage; titrate dosage gradually.a
Cautions for Trihexyphenidyl
Contraindications
-
Known hypersensitivity to trihexylphenidyl or any ingredient in the formulation.c
Warnings/Precautions
Warnings
Ophthalmic Effects
Possible increased ocular tension.a Possible precipitation of glaucoma in patients receiving prolonged therapy.a c
Use with caution in patients with glaucoma.a c
Periodic gonioscopic evaluation and intraocular pressure monitoring recommended.a b
General Precautions
Tardive Dyskinesia
Antiparkinsonian agents do not alleviate symptoms of tardive dyskinesia and may aggravate these symptoms.a
Cardiovascular Effects
Possible tachycardia;a use with caution and carefully monitor patients with cardiac disease or hypertension.a c
GU Effects
Possible urinary hesitancy and retention;a c use with caution and carefully monitor patients with prostatic hypertrophy or obstructive disease of the GU tract.a c
CNS Effects
Possible mental confusion, disorientation, agitation, hallucinations, and psychotic-like symptoms.a
GI Effects
Possible decreased intestinal mobility and paralytic ileus; use with caution in patients with obstructive diseases of the GI tract.a
Specific Populations
Pregnancy
Category C.d
Geriatric Use
Possibility exists of greater sensitivity to the drug in some geriatric individuals.a
Hepatic Impairment
Use with caution; careful monitoring recommended.a
Renal Impairment
Use with caution; careful monitoring recommended.a
Common Adverse Effects
Dry mouth, blurred vision, dizziness, nausea, nervousness.a
Interactions for Trihexyphenidyl
Specific Drugs
Drug |
Interaction |
|
---|---|---|
Anticholinergic agents |
Increased risk of adverse anticholinergic effectsc |
Trihexyphenidyl Pharmacokinetics
Absorption
Rapidly absorbed from the GI tract following oral administration.b
Onset
Following oral adminstration, onset of action occurs within 1 hour.b
Duration
6–12 hours.b
Elimination
Elimination Route
Excreted principally in urine, probably as unchanged drug.b
Stability
Storage
Oral
Elixir
Tablets
20–25°C.a
Actions
-
Exhibits atropine-like action and exerts antispasmodic effects on parasympathetic-innervated peripheral structures, including smooth muscle.a b
-
Exact mechanism of action in parkinsonian syndrome not understood; may result from blockade of efferent impulses and from central inhibition of cerebral motor centers.b
-
Competitively inhibits acetylcholine or other cholinergic stimuli at autonomic effectors innervated by postganglionic nerves.c
-
Exhibits weak mydriatic, antisialagogue, and cardiovagal blocking effects.b
Advice to Patients
-
Potential for drug to impair mental alertness or physical coordination; use caution when driving or operating machinery until effects on individual are known.a
-
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as concomitant illnesses.a
-
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.a
-
Importance of informing patients of other important precautionary information.a (See Cautions.)
Preparations
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.
* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name
Routes |
Dosage Forms |
Strengths |
Brand Names |
Manufacturer |
---|---|---|---|---|
Oral |
Elixir |
2 mg/5 mL* |
Trihexyphenidyl Hydrochloride Elixir |
Mikart, Pharmaceutical Associates, Pharmaceutical Ventures |
Tablets |
2 mg* |
Trihexyphenidyl Hydrochloride Tablets |
URL, Vintage, Watson, West-Ward |
|
5 mg* |
Trihexyphenidyl Hydrochloride Tablets |
URL, Vintage, Watson, West-Ward |
AHFS DI Essentials™. © Copyright 2021, Selected Revisions October 1, 2007. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.
References
a. Watson Laboratories Inc. trihexyphenidyl hydrochloride tablets, USP. prescribing information. Corona, CA; 2005 May.
b. AHFS drug information 2006. McEvoy GK, ed. Trihexyphenidyl. Bethesda, MD: American Society of Health-System Pharmacists; 2006:1256.
c. AHFS drug information 2006. McEvoy GK, ed. Antimuscarinics/Antispasmodics General Statement. Bethesda, MD: American Society of Health-System Pharmacists; 2006:1257-64].
d. Briggs GG, Freeman RK, Yaffe SJ. Drugs in pregnancy and lactation, 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005:1628
e. Pharmaceutical Associates, Inc. Trihexyphenidyl HCl elixir prescribing information. Greenville, SC; 2002 May.
More about trihexyphenidyl
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- Drug class: anticholinergic antiparkinson agents
Consumer resources
Professional resources
- Trihexyphenidyl (Professional Patient Advice)
- Trihexyphenidyl (FDA)
- Trihexyphenidyl Elixir (FDA)
- Trihexyphenidyl Oral Solution (FDA)