Symptoms
Symptoms of overdose with antimuscarinic agents include flushing and dryness of the skin, dilated pupils, dry mouth and tongue, tachycardia, rapid respiration, hyperpyrexia, hypertension, nausea, vomiting. A rash may appear on the face or upper trunk. Symptoms of CNS stimulation include restlessness, confusion, hallucinations, paranoid and psychotic reactions, incoordination, delirium and occasionally convulsions. In severe overdose, CNS depression may occur with coma, circulatory and respiratory failure and death.
Treatment
Treatment should always be supportive. An adequate airway should be maintained. Diazepam may be administered to control excitement and convulsions but the risk of central nervous system depression should be considered. Hypoxia and acidosis should be corrected. Antiarrhythmic drugs are not recommended if dysrhythmias occur.
24 months
None known
Monohydrate citric acid, sodium benzoate, propylene glycol, glycerol, ethanol, blackcurrant flavour, sucrose and purified water.
A blackcurrant scented and flavoured colourless syrup.
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.
Worsening of myasthenia gravis may occur.
Eye disorders: Dilatation of the pupils with loss of accommodation and photophobia, raised intraocular pressure.
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. Healthcare professional are asked to report any suspected adverse reactions via Yellow Card Scheme at www.mhra.gov.uk/yellowcard
No formal preclinical studies have been undertaken with Trihexyphenidyl Syrup, as its active ingredient is a well established pharmaceutical.
Parkinsonism and drug induced extrapyramidal syndrome.
Pharmacotherapeutic group: anti-cholinergic agents
ATC code: NO4A A 01
Trihexyphenidyl is a tertiary amine antimuscarinic. It also has a direct antispasmodic action on smooth muscle.
Trihexyphenidyl is well absorbed from the gastro-intestinal tract.
01 March 2017
Trihexyphenidyl Hydrochloride 5mg/5ml Syrup
Rosemont Pharmaceuticals Ltd
Rosemont House
Yorkdale Industrial Park
Braithwaite Street
Leeds
LS11 9XE
UK
Do not store above 25°C. Do not refrigerate or freeze. Store in the original package.
200ml pack size in amber glass bottle with child resistant cap.
PL00427/0222
Pregnancy
There is inadequate information regarding the use of trihexyphenidyl in pregnancy. Animal studies are insufficient with regard to effects on pregnancy, embryonal/foetal development, parturition and postnatal development. The potential risk for humans is unknown. Trihexyphenidyl should not be used during pregnancy unless clearly necessary.
Breastfeeding
It is unknown whether trihexyphenidyl is excreted in human breast milk. The excretion of trihexyphenidyl in milk has not been studied in animals. Infants may be very sensitive to the effects of antimuscarinic medications. Trihexyphenidyl should not be used during breast feeding.
Each 5ml contains 5mg trihexyphenidyl hydrochloride
Excipients with known effect:
Sucrose: 2.6mg/5ml
Ethanol: less than 100mg/5ml
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.
Anticholinergic medications, including trihexyphenidyl, should not be withdrawn abruptly in patients on long-term therapy, to avoid recurrence of the original symptoms and possible anticholinergic rebound. Prescribers should be aware that trihexyphenidyl may be the subject of abuse due to its euphoric or hallucinogenic properties.
Since atropine-like drugs may cause psychiatric symptoms such as confusion, delusion and hallucinations, trihexyphenidyl should be used with extreme caution in elderly patients.
Incipient glaucoma may be precipitated by para-sympatholytic drugs such as trihexyphenidyl.
Hypertension, cardiac, liver or kidney disorders are not contraindicated, 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 myasthenia gravis.
Patients with arteriosclerosis or those with history of idiosyncrasy to other drugs may be more likely to develop severe mental reactions to trihexyphenidyl.
Excipient Warnings:
This product contains -
- Sucrose - 2.6g per 5ml. Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-maltase insufficiency should not take this medicine.
- Ethanol - This medicinal product contain small amounts of ethanol (alcohol), less than 100mg per 5ml.
Patients should be warned of the potential hazards of driving or operating machinery if they experience blurred vision or a reduction in alertness.
Posology
Adults and Elderly:
Initial dose 2mg. Subsequent doses up to 20mg as recommended by a physician.
Children:
Not recommended.
Method of administration
For oral administration
No special requirements for disposal.
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
07 November 2011
Concurrent use of trihexyphenidyl hydrochloride with drugs possessing antimuscarinic effects increases the side-effects such as blurred vision, dry mouth, urine retention and constipation; concomitant use can also lead to confusion in the elderly.
Concurrent use of trihexyphenidyl hydrochloride with nefopam increases antimuscarinic effects.
Concurrent use of tricyclic anti-depressants and monoamine oxidase inhibitors with trihexyphenidyl hydrochloride increases the antimuscarinic side-effects.
Concurrent use of trihexyphenidyl hydrochloride with ketoconazole reduces the absorption of the latter.
Concurrent use of trihexyphenidyl with anti-histamine increases the antimuscarinic side-effects.
Concurrent use of trihexyphenidyl hydrochloride with disopyramide increases the antimuscarinic effects.
Concurrent use of trihexyphenidyl with phenothiazines increases the antimuscarinic effect (but reduces plasma concentrations).
Increased antimuscarinic side-effects are observed with amantadine and absorption of levodopa is possibly reduced.
Concurrent use of trihexyphenidyl hydrochloride with metoclopramide and domperidone antagonises the gastro-intestinal effects.
Antimuscarinics reduce the effects of sublingual nitrates due to failure to dissolve under the tongue owing to dry mouth
Parasympathomimetics antagonise the effects of antimuscarinics.
