pharmacopeia
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/api/v1/drug/trihexyphenidyl

Mechanism of action

Sourced from openFDA

Mechanism-of-action class: Unknown Cellular or Molecular Interaction.

Indications

Sourced from openFDA
  • Trihexyphenidyl is indicated as an adjunct in the treatment of all forms of parkinsonism (postencephalitic, arteriosclerotic, and idiopathic). It is often useful as adjuvant therapy when treating these forms of parkinsonism with levodopa.

Contraindications

Sourced from openFDA
  • Trihexyphenidyl is contraindicated in patients with hypersensitivity to trihexyphenidyl or to any of the other ingredients. Trihexyphenidyl is also contraindicated in patients with narrow angle glaucoma.contraindicated

Dosage & administration

Sourced from openFDA

Dosage should be individualized. The initial dose should be low and then increased gradually, especially in patients over 60 years of age.Whether trihexyphenidyl may best be given before or after meals should be determined by the way the patient reacts. Postencephalitic patients, who are usually more prone to excessive salivation, may prefer to take it after meals and may, in addition, require small amounts of atropine which, under such circumstances, is sometimes an effective adjuvant. If trihexyphenidyl tends to dry the mouth excessively, it may be better to take it before meals, unless it causes nausea. If taken after meals, the thirst sometimes induced can be allayed by mint candies, chewing gum or water. Abrupt withdrawal of treatment for parkinsonism may result in acute exacerbation of parkinsonism symptoms; therefore, abrupt withdrawal should be avoided. Abrupt withdrawal of treatment may result in neuroleptic malignant syndrome (NMS) (See WARNINGS ). Idiopathic Parkinsonism As initial therapy for parkinsonism, 1 mg of trihexyphenidyl hydrochloride may be administered the first day. The dose may then be increased by 2 mg increments at intervals of three to five days, until a total of 6 to 10 mg is given daily. The total daily dose will depend upon what is found to be the optimal level. Many patients derive maximum benefit from this daily total of 6 to 10 mg, but some patients, chiefly those in the postencephalitic group, may require a total daily dose of 12 to 15 mg.

Warnings & precautions

Sourced from openFDA

Patients to be treated with trihexyphenidyl should have a gonioscope evaluation prior to initiation of therapy and close monitoring of intraocular pressures. The use of anticholinergic drugs may precipitate angle closure with an increase in intraocular pressure. If blurring of vision occurs during therapy, the possibility of narrow angle glaucoma should be considered. Blindness has been reported due to aggravation of narrow angle glaucoma. (See CONTRAINDICATIONS and ADVERSE REACTIONS ). Trihexyphenidyl should be administered with caution in hot weather, especially when given concomitantly with other atropine-like drugs to the chronically ill, alcoholics, those who have central nervous system disease, or those who do manual labor in a hot environment. Anhidrosis may occur more readily when some disturbance of sweating already exists. If there is evidence of anhidrosis, the possibility of hyperthermia should be considered. Dosage should be decreased so that the ability to maintain body heat equilibrium via perspiration is not impaired. Severe anhidrosis and fatal hyperthermia have occurred with the use of anticholinergics under the conditions described above. Neuroleptic Malignant Syndrome A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with dose reduction or discontinuation of trihexyphenidyl.

Adverse reactions

Sourced from openFDA

Minor side effects, such as dryness of the mouth, blurred vision, dizziness, mild nausea or nervousness, will be experienced by 30 to 50 percent of all patients. These sensations, however, are much less troublesome with trihexyphenidyl than with belladonna alkaloids and are usually less disturbing than unalleviated parkinsonism. Such reactions tend to become less pronounced, and even to disappear, as treatment continues. Even before these reactions have remitted spontaneously, they may often be controlled by careful adjustment of dosage form, amount of drug, or interval between doses. Isolated instances of suppurative parotitis secondary to excessive dryness of the mouth, skin rashes, dilatation of the colon, paralytic ileus, and certain psychiatric manifestations such as delusions, hallucinations, and paranoia, all of which may occur with any of the atropine-like drugs, have been reported rarely with trihexyphenidyl. Potential side effects associated with the use of any atropine-like drugs, including trihexyphenidyl, include cognitive dysfunctions, including confusion and memory impairment; constipation, drowsiness, urinary hesitancy or retention, tachycardia, dilation of the pupil, increased intraocular pressure, choreiform movements, weakness, vomiting, and headache. Exacerbation of parkinsonism with abrupt treatment withdrawal has been reported. Neuroleptic malignant syndrome with abrupt treatment withdrawal has been reported (See WARNINGS, Neuroleptic Malignant Syndrome ).

Use in specific populations

Sourced from openFDA

Pregnancy Teratogenic Effects Pregnancy Category C Animal reproduction studies to evaluate teratogenic and embryotoxic potential have not been conducted with trihexyphenidyl. It is also not known whether trihexyphenidyl can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Trihexyphenidyl should be given to a pregnant woman only if clearly needed.

Overdosage

Sourced from openFDA

The mean oral LD 50 of trihexyphenidyl has been reported to be 365 mg/kg (range, 325 to 410 mg/kg) in mice and 1660 mg/kg (1420 to 1940 mg/kg) in rats. At a dose of 40 mg/kg, dogs have exhibited emesis, restlessness followed by drowsiness, equilibrium disturbances, and mydriasis. In humans, doses up to 300 mg (5 mg/kg) have been ingested without fatalities or sequelae. However, rare cases of death associated with trihexyphenidyl overdosages taken in conjunction with other CNS-depressant agents have been reported or in patients with a compromised respiratory condition. Trihexyphenidyl blood concentrations associated with the fatalities ranged from 0.03 to 0.80 mg/l. Signs and Symptoms Overdosage with trihexyphenidyl produces typical central symptoms of atropine intoxication (the central anticholinergic syndrome). Correct diagnosis depends upon recognition of the peripheral signs of parasympathetic blockade, including dilated and sluggish pupils; warm, dry skin; facial flushing; decreased secretions of the mouth, pharynx, nose, and bronchi; foul-smelling breath; elevated temperature; tachycardia, cardiac arrhythmias; decreased bowel sounds; and urinary retention.

Approval history

Sourced from openFDA
  • Nov 26, 1974ANDAANDA084363Watson Labs
  • Dec 6, 1974ANDAANDA084364Watson Labs
  • Apr 17, 1997ANDAANDA040177Pharm Assoc
  • Dec 24, 1998ANDAANDA040254Novitium Pharma
  • Sep 27, 1999ANDAANDA040251Chartwell Rx
  • Nov 17, 2010ANDAANDA091630Natco Pharma Ltd

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
941 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Off Label Use707.4%
  2. 2Drug Interaction596.3%
  3. 3Nausea525.5%
  4. 4Coma505.3%
  5. 5Ischaemic Stroke424.5%
  6. 6Respiratory Distress414.4%
  7. 7Respiratory Failure373.9%
  8. 8Somnolence353.7%
  9. 9Fall343.6%
  10. 10Areflexia333.5%
  11. 11Cerebrovascular Accident333.5%
  12. 12Pneumonia Aspiration333.5%
  13. 13Tremor333.5%
  14. 14Brain Scan Abnormal323.4%
  15. 15Drug Abuse323.4%

Literature

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Recent PubMed references pinned to Trihexyphenidyl as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 8 most recently updated of 8 ClinicalTrials.gov registrations naming Trihexyphenidyl as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Trihexyphenidyl work?
Mechanism-of-action class: Unknown Cellular or Molecular Interaction.
What is Trihexyphenidyl used for?
According to FDA labeling, Trihexyphenidyl carries indications including: Trihexyphenidyl is indicated as an adjunct in the treatment of all forms of parkinsonism (postencephalitic, arteriosclerotic, and idiopathic). It is often useful as adjuvant therapy when treating these forms of parkinsonism with levodopa.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Trihexyphenidyl?
Trihexyphenidyl is classified as Tertiary amines, Unknown Cellular or Molecular Interaction, Decreased Parasympathetic Acetylcholine Activity, Decreased Striated Muscle Contraction, Smooth Muscle Tone Alteration.
What are the contraindications for Trihexyphenidyl?
Trihexyphenidyl labeling lists contraindications including: Trihexyphenidyl is contraindicated in patients with hypersensitivity to trihexyphenidyl or to any of the other ingredients. Trihexyphenidyl is also contraindicated in patients with narrow angle glaucoma.. Always consult the full prescribing information and a clinician.
Note. Data for trihexyphenidyl is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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