Adult: Initially, 2.5 mg tid, increased gradually by 2.5-5 mg every 2-3 days if required or by 2.5 mg daily for drug-induced extrapyramidal symptoms. Maintenance: 10-30 mg daily in 3-4 divided doses. Up to 60 mg daily may be required in some cases. Elderly: Lower doses are required.
This drug may cause blurred vision, dizziness, confusion or disorientation, if affected, do not drive or operate machinery.
Monitor symptoms of extrapyramydal syndrome or Parkinson's disease, pulse, anticholinergic effects (e.g. CNS, bowel and bladder function).
Symptoms: Stimulant effects (e.g. agitation, restlessness, confusion, sleeplessness lasting up to ≥24 hr; euphoria, anxiety, aggressive behaviour; dilated pupils that are nonreactive to light; disorientation (lasting for 1-4 days); CNS depression (e.g. somnolence, reduced consciousness, and occasionally coma); tachycardia. Management: Use activated charcoal to reduce absorption w/in 1-2 hr of ingestion (or possibly longer in view of its likely effects on gastric motility). Consider gastric lavage only if clinically appropriate. May give diazepam inj if convulsions occur.
Increased plasma concentrations w/ paroxetine. Enhanced anticholinergic action w/ MAOIs and other anticholinergic drugs. Reduced therapeutic effect w/ cholinergic drugs. May antagonise the effect of parasympathomimetic agents. May reduce the absorption and therapeutic effect of sublingual or buccal nitrate tab. May reduce the efficacy of levodopa. May antagonise the GI effects of cisapride, domperidone and metoclopramide. May potentiate the vagolytic effects of quinidine. May reduce the absorption of ketoconazole.
Alcohol may potentiate the CNS effects of procyclidine.
Description: Procyclidine is postulated to act by blocking excess acetylcholine at the muscarinic receptor; many of its effects are due to its pharmacologic similarities w/ atropine. Onset: W/in 5-20 min (IV). Duration: Up to 4 hr (IV). Pharmacokinetics: Absorption: Adequately absorbed from the GI tract. Bioavailability: 75% (oral). Time to peak plasma concentration: Approx 1 hr. Distribution: Disappears rapidly from the tissues. Volume of distribution: 1 L/kg. Metabolism: Undergoes hepatic metabolism (approx one-fifth of oral dose) by CYP450 isoenzymes, then conjugated w/ glucuronic acid. Excretion: Via urine as unchanged drug (small amounts). Plasma elimination half-life: Approx 12 hr (oral/IV).