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Antimuscarinic (Parkinsonian) Pregnancy: SPC section 4.6, verbatim: 'There is inadequate evidence of safety in human pregnancy, and, although it has been widely used for many years without apparent ill consequence, if considered necessary orphenadrine should be used with caution during pregnancy. Animal studies have not revealed any hazard.' Breast-feeding, verbatim: 'It is probably excreted in milk during lactation. Although the quantity is unlikely to be significant at normal therapeutic doses, if considered necessary orphenadrine should be used with caution during breast feeding.' Section 4.4 additionally advises caution in pregnancy and breastfeeding.

Orphenadrine hydrochloride

Brand names: Disipal, Biorphen

Orphenadrine hydrochloride is an antimuscarinic agent used to relieve the symptoms of Parkinson's disease, particularly tremor and rigidity, and drug-induced parkinsonism.

Adult dose

Dose: Parkinsonism (this page's primary indication) in adults and the elderly: initially 150 mg daily in divided doses, increasing by 50 mg every two or three days until maximum benefit is obtained. Optimal dosage is usually 250 mg to 300 mg daily in divided doses in idiopathic and post-encephalitic parkinsonism; 100 mg to 150 mg daily in divided doses in arteriosclerotic parkinsonism; and 150 mg to 300 mg daily in divided doses in 'the neuroleptic syndrome' (the SPC's own wording for the third indication - confirm the intended indication against the current SmPC before applying it).
Route: Oral. The product quoted is Orphenadrine Hydrochloride 50 mg/5 ml Oral Solution; the SPC expresses every figure above in mg of orphenadrine hydrochloride, not in millilitres or tablets.
Frequency: Daily total given in divided doses, titrated upwards by 50 mg every two or three days until maximum benefit is obtained. The SPC does not specify how many divided doses per day.
Max: 400 mg daily in divided doses. SPC section 4.2, verbatim: 'Maximal dosage is 400mg daily in divided doses.' This is the ceiling for the same indication, route and population as the dose above.
Section 4.2 is complete in this bundle (it ends with the paediatric statement); the truncation marker in this bundle falls inside section 4.4/4.5, not inside the posology. ELDERLY, verbatim: 'The elderly may be more susceptible to side effects at doses which are clinically optimal.' The SPC gives no separate elderly dose - the adult regimen above is stated for 'Adults and the elderly'. STOPPING: section 4.4 advises 'Avoid abrupt discontinuation of treatment.'

Paediatric dose

Dose: Not recommended. SPC section 4.2 states in full: 'Children: Not recommended for use in children.'
Route: Not applicable - the SPC gives no paediatric route, regimen or age band.
No paediatric figure exists in this source and none has been derived from the adult dose. If treatment of a child is being considered, verify against a children's formulary and specialist advice.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to orphenadrine or to any of the excipients (section 4.3)
  • Prostatic hypertrophy (section 4.3)
  • Tardive dyskinesia (section 4.3). Section 4.4 adds: 'Anti-muscarinic agents such as orphenadrine are not effective in the treatment of tardive dyskinesia which may be made worse and should not be used in patients with this condition.'
  • Porphyria (section 4.3)
  • Urinary retention (section 4.3)
  • Paralytic ileus or pyloric stenosis - 'where use may lead to obstruction' (section 4.3)
  • Glaucoma, or too narrow an angle between iris and cornea - 'as it may raise intra-ocular pressure' (section 4.3)
  • Patients at risk of developing hyperpyrexia - 'Not indicated for use in patients at risk of developing hyperpyrexia.' (section 4.3)
  • Section 4.3 also directs that orphenadrine 'must also be used with caution in elderly men'

Side effects

  • Immune system: hypersensitivity
  • Nervous system: dizziness, restlessness, sedation, confusion, nervousness, hallucinations, convulsions, insomnia, euphoria, co-ordination disturbances, light-headedness, memory disturbances
  • Eye: accommodation disorders
  • Cardiac: tachycardia
  • Gastrointestinal: dry mouth, nausea, gastrointestinal disturbances, constipation
  • Renal and urinary: urinary retention
  • Section 4.8 presents these in a frequency table (common / uncommon / rare); the fetched text flattens the table columns, so no frequency band has been assigned to any individual reaction here.

Interactions

  • 'Effects may be enhanced by concomitant administration of anticholinergic drugs.' (section 4.5)
  • 'May be provocation of dextropropoxyphene side effects during concurrent administration.' (section 4.5)
  • Anti-muscarinic effects may be enhanced by other medicines with anti-muscarinic properties - antihistamines, antispasmodics, tricyclic antidepressants, phenothiazines, dopaminergic anti-parkinsonian drugs including amantadine, and anti-arrhythmics (section 4.5)
  • INCOMPLETE LIST: section 4.5 is cut off at the source-fetch limit in this bundle, so the three items above are not the whole interaction section. Check the current SmPC.

Monitoring

  • Heart rate - 'Anti-muscarinic agents, such as orphenadrine, should be used with caution in patients with pre-existing tachycardia (e.g. in heart failure, thyrotoxicosis) as they may cause further acceleration of the heart rate.' (section 4.4)
  • Anticholinergic side effects in older people - 'The elderly may be more susceptible to side effects at doses which are clinically optimal' (section 4.2); use with caution in the elderly (section 4.4) and in elderly men (section 4.3)
  • Micturition difficulties and urinary retention (section 4.4)
  • Concomitant hypertension, cardiac, renal or hepatic dysfunction - 'Care should be taken when using in patients with concomitant hypertension, cardiac, renal or hepatic dysfunction.' (section 4.4)
  • Do not stop abruptly - 'Avoid abrupt discontinuation of treatment.' (section 4.4)
  • Misuse potential - 'For some patients orphenadrine may be a drug of abuse.' (section 4.4)

Clinical monograph

How it works

It blocks central muscarinic acetylcholine receptors, helping to restore the dopamine-acetylcholine balance within the basal ganglia.

Prescribing in practice

  • Marked antimuscarinic effects make it hazardous in older adults and in those with glaucoma, prostatic enlargement or urinary retention, and abrupt withdrawal should be avoided.
  • Use cautiously alongside other anticholinergic, sedating, or serotonergic drugs because of additive adverse effects.
  • It can impair cognition and worsen confusion, so it is generally avoided where dementia or significant cognitive impairment is present.

Monitoring

Monitor for antimuscarinic effects such as dry mouth, blurred vision, constipation, urinary retention and confusion, especially in older patients.

Counselling the patient

  • This medicine may cause dry mouth, blurred vision, constipation or difficulty passing urine.
  • It can affect alertness, so take care with driving and avoid stopping it suddenly without advice.

Evidence & guidelines

Antimuscarinics like orphenadrine are long-established for parkinsonian tremor; NICE advises caution given limited evidence and a poor tolerability profile in older people.

Reference: NICE NG71; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Pathways