Trihexyphenidyl: Uses, Side Effects, Dosage - Drugvu

ℹ️ Compiled from public regulatory records · Last regulator revision: May 15, 2026🚩 Report this page

Trihexyphenidyl

Tertiary Amines

GB MHRACA Health Canada

Drug class: Tertiary Amines
Availability: See label
Routes: Oral
Markets covered: 2
Products on record: 15

Overview

Trihexyphenidyl is an active pharmaceutical ingredient in the Tertiary Amines group (N04AA). The information below is compiled per regulator from the product labels on record, with direct links to the original documents.

Regulatory status by market

Market	Regulator	Products	Last revision
GB United Kingdom	MHRA	13	May 15, 2026
CA Canada	Health Canada	2	February 16, 2026

GBUnited Kingdom· MHRA

13 products

Uses

GBOfficial regulatory label· revised July 25, 2025[1]

1. Treatment of parkinsonism 2. Prevention and control of drug-induced extrapyramidal symptoms (excluding tardive dyskinesia)

How to take

CACanada· Health Canada

2 products

2 products on record with this regulator. Detailed label text (uses, dosage, side effects) is being ingested — the original document is linked under Sources [2].

Drug interactions

Known interactions involving Trihexyphenidyl. Select one for details. This list is informational and not a complete interaction checker.

Potassium Chloride Potassium Citrate Topiramate Zonisamide Acebutolol Acetylcholine Aclidinium Acrivastine Alfentanil Alprazolam Amantadine Ambenonium Amitriptyline Amobarbital Amoxapine Apomorphine Apraclonidine Arbutamine Aripiprazole Asenapine Atenolol Atropine Azatadine Baclofen Benzhydrocodone Betaxolol Bethanechol Biperiden Bisoprolol Botulinum Toxin Type A Botulinum Toxin Type B Brexanolone Brexpiprazole Brimonidine Brivaracetam Bromocriptine Brompheniramine Buprenorphine Buspirone Butabarbital Butalbital Butorphanol Cannabidiol Carbamazepine Carbamoylcholine Carbinoxamine Cariprazine Carisoprodol Carteolol Carvedilol Cenobamate Cetirizine Cevimeline Chlorcyclizine Chlordiazepoxide Chlormezanone Chlorphenesin Chlorpheniramine Chlorpromazine Chlorzoxazone Citalopram Clemastine Clidinium Clobazam Clomipramine Clonazepam Clonidine Clorazepate Clozapine Codeine Cyclizine Cyclobenzaprine Cyproheptadine Dantrolene Darifenacin Demecarium Desipramine Desvenlafaxine Deutetrabenazine Dexbrompheniramine Dexmedetomidine Dextromethorphan Dezocine Diazepam Dicyclomine Dihydrocodeine Dimenhydrinate Diphenhydramine Disopyramide Donepezil Doxepin Doxylamine Dronabinol Droperidol Duloxetine Edrophonium Eluxadoline Escitalopram Esketamine Eslicarbazepine Estazolam Eszopiclone Ethanol Ethchlorvynol Ethosuximide Ethotoin Ezogabine Fentanyl Fesoterodine Flavoxate Flibanserin Fluoxetine Fluphenazine Flurazepam Fluvoxamine Fosphenytoin Gabapentin Galantamine Glycopyrronium Guanidine Halazepam Haloperidol Homatropine Hydrocodone Hydromorphone Hydroxyzine Hyoscyamine Iloperidone Imipramine Ipratropium Isoflurophate Ketamine Ketoconazole Labetalol Lamotrigine Lasmiditan Lemborexant Levetiracetam Levocetirizine Levodopa Levorphanol Lofexidine Loperamide Lorazepam Loxapine Lumateperone Lurasidone Magnesium Hydroxide Maprotiline Meclizine Memantine Mepenzolate Meperidine Mephenytoin Mephobarbital Meprobamate Mesoridazine Metaxalone Methadone Methdilazine Methocarbamol Methohexital Methotrimeprazine Methscopolamine Methsuximide Metoclopramide Metoprolol Metyrosine Midazolam Mirtazapine Molindone Morphine Nabilone Nadolol Nalbuphine Nebivolol Nefazodone Neostigmine Nortriptyline Olanzapine Oliceridine Olopatadine Opicapone Opium Orphenadrine Oxazepam Oxcarbazepine Oxybutynin Oxycodone Oxymorphone Paliperidone Paraldehyde Paroxetine Penbutolol Pentazocine Pentobarbital Perampanel Pergolide Perphenazine Phenindamine Phenobarbital Phensuximide Phenylephrine Phenyltoloxamine Phenytoin Physostigmine Pilocarpine Pimozide Pindolol Pramlintide Pregabalin Primidone Prochlorperazine Procyclidine Promazine Promethazine Propantheline Propiomazine Propoxyphene Propranolol Protriptyline Prucalopride Pyridostigmine Pyrilamine Quazepam Quetiapine Ramelteon Rasagiline Remifentanil Remimazolam Revefenacin Risperidone Rivastigmine Rotigotine Rufinamide Scopolamine Secobarbital Sertraline Solifenacin Sotalol

Showing 240 of 356. Type above to find a specific drug.

Interaction data compiled from DDInter (academic, CC-BY). Severity classification only - this is not a complete interaction checker and not medical advice.

Sources & citations

[1]MHRA (UK) · PL401470080 · revised July 25, 2025
[2]Health Canada (DPD) · 00545058 · revised February 16, 2026

Information on this page is compiled from public regulatory records. Drugvu is not affiliated with any regulator or pharmaceutical manufacturer. This is not medical advice. Always consult a qualified healthcare professional.

Posology Adults only:
Optimal dosage should always be determined empirically, usually by initiating therapy at a relatively low level and by subsequent graduated increments. The usual dosage for Parkinsonism is 6 - 10 mg per day although some patients chiefly in the post-encephalitic group may require an average total dose of 12 - 15 mg daily.
It should be given orally either three or four times a day at mealtimes. Normal dosage for drug-induced Parkinsonism is usually between 5 mg and 15 mg per day, although some cases have been controlled by 1 mg daily. In all cases, trihexyphenidyl dosage should be increased or decreased only by small increments over a period of several days.
In initial therapy the dose should be 1mg the first day, 2mg the second day with further increases of 2mg per day at three to five-day intervals until the optimum dose is reached. If patients are already being treated with other parasympathetic inhibitors, trihexyphenidyl should be substituted as part of the therapy.
When trihexyphenidyl is used concomitantly with levodopa the usual dose of each may need to be reduced. Careful adjustment is necessary, depending on side effects and the degree of symptom control. Trihexyphenidyl dosage of 3-6mg daily in divided doses, is usually adequate.
Trihexyphenidyl may be taken before or after meals according to the way the patient reacts. 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, induced thirst can be allayed by peppermint, chewing gum or water.
Treatment of drug-induced extrapyramidal disorder:
The size and frequency of dose of trihexyphenidyl needed to control extrapyramidal reactions to commonly employed tranquillisers, notably the phenothiazines, thioxanthenes, and butyrophenones must be determined empirically. The total daily dosage usually ranges between 5 and 15mg, although in some cases, these reactions have been controlled by as little as 1mg daily.
Satisfactory control may sometimes be more rapidly achieved by temporarily reducing the dosage of both drugs until the desired ataractic effect is retained without concomitant extrapyramidal reactions. It is sometimes possible to maintain the patient on reduced trihexyphenidyl dosage after the reactions have remained under control for several days.
Since these reactions may remain in remission for long periods after discontinuation of trihexyphenidyl therapy, such therapy should be of minimal duration and discontinued after symptoms have subsided for a reasonable period of time.
Elderly:
Patients over 65 years of age tend to be relatively more sensitive and require smaller amounts of the drug.
Paediatric population:
Not recommended. Method of administration For oral use.

Side effects & warnings

GBOfficial regulatory label· Adverse reactions· revised July 25, 2025[1]

Modern clinical data required to determine the frequency of undesirable effects are lacking for trihexyphenidyl. Minor side effects such as dryness of mouth, constipation, blurring of vision, dizziness, mild nausea or nervousness will be experienced by 30-50% of all patients.
These reactions tend to become less pronounced as treatment continues. Patients should be allowed to develop a tolerance using the smaller initial dose until an effective level is reached.
Immune system disorders:
Hypersensitivity.
Psychiatric disorders:
Nervousness, restlessness, confusional states, agitation, delusions, hallucinations, insomnia, especially in the elderly and patients with arteriosclerosis. The development of psychiatric disturbances may necessitate discontinuation of treatment.
Euphoria may occur. There have been reports of abuse of trihexyphenidyl due to its euphoric and hallucinogenic properties.
Nervous system disorders:
Dizziness. Impairment of immediate and short-term memory function has been reported. 4). 4).
Cardiac disorders:
Tachycardia.
Respiratory, thoracic and mediastinal disorders:
Decreased bronchial secretions.
Gastrointestinal disorders:
Dry mouth with difficulty swallowing, constipation, nausea, vomiting.
Skin and subcutaneous tissue disorders:
Flushing and dryness of skin, skin rashes.
Renal and urinary disorders:
Urinary retention, difficulty in micturition.
General disorders:
Thirst, pyrexia. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.
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GBOfficial regulatory label· Warnings and precautions· revised July 25, 2025[1]

Precautions:
Since the use of trihexyphenidyl may, in some cases, continue indefinitely, the patient should be under careful observation over the long term. It should be administered with care to avoid allergic or other untoward reactions. Except in the case of vital complications, abrupt discontinuation of the drug should be avoided.
Incipient glaucoma may be precipitated by para-sympatholytic drugs such as trihexyphenidyl. Hypertension, cardiac, liver or kidney disorders are not contra-indicated, but such patients should be followed closely. As trihexyphenidyl may provoke or exacerbate tardive dyskinesia, it is not recommended for use in patients with this condition.
Trihexyphenidyl should be used with caution in patients with glaucoma, obstructive disease of the gastro-intestinal or genito-urinary tracts, and in elderly males with possible prostatic hypertrophy. Since trihexyphenidyl has been associated with clinical worsening of myasthenia gravis, the drug should be avoided or used with great caution in patients with this condition.
2).
Warnings:
Trihexyphenidyl may be the subject of abuse (on the basis of hallucinogenic or euphoriant properties, common to all anti-cholinergic drugs) if given in sufficient amounts. Patients with rare hereditary problems of galactose intolerance, total lactase deficiency or glucose-galactose malabsorption should not take this medicine.

This is not medical advice. Consult a qualified healthcare professional.