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 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 this condition.
Since certain psychiatric manifestations such as confusion, delusions and hallucinations, all of which may occur with any of the atropine-like drugs, have been reported rarely with trihexyphenidyl, it should be used with extreme caution in elderly patients (see section 4.2).
Warnings: Trihexyphenidyl may be the subject of abuse (on the basis of hallucinogenic and euphoriant properties, common to all anti-cholinergic drugs) if given in sufficient amounts.
Excipient Warnings:
This product contains –
• Sucrose – 2.6g per 5ml. Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
• Ethanol – this medicine contains 0.817 mg of alcohol (ethanol) in each 5ml, which is equivalent to 0.1634 mg/ml. The amount in 5ml of this medicine is equivalent to less than 1 ml beer or 1 ml wine. The small amount of alcohol in this medicine will not have any noticeable effects.
• Propylene glycol – this medicine contains 19.27mg per 5ml. Co-administration with any substrate for alcohol dehydrogenase such as ethanol may induce adverse effects in children less than 5 years old.
While propylene glycol has not been shown to cause reproductive or developmental toxicity in animals or humans, it may reach the foetus and was found in milk. As a consequence, administration of propylene glycol to pregnant or lactating patients should be considered on a case by case basis.
Medical monitoring is required in patients with impaired renal or hepatic functions because various adverse events attributed to propylene glycol have been reported such as renal dysfunction (acute tubular necrosis), acute renal failure and liver dysfunction.
• Sodium benzoate – this medicine contains 5.9 mg sodium benzoate in each 5ml, which is equivalent to 1.18 mg/ml.
• Sodium – this medicine contains less than 1mmol sodium (23 mg) per 5ml, that is to say essentially 'sodium-free'.