Orphenadrine


Full Prescribing Info
Dosage/Direction for Use

Oral
Muscle spasms
Adult: As orphenadrine citrate: 100 mg twice daily.

Oral

Parkinsonism
Adult: As orphenadrine HCl: Initially, 150 mg daily in divided doses, increased by 50 mg every 2-3 days according to response. Usual maintenance dose: 150-300 mg daily. Max: 400 mg daily in divided doses.

Parenteral

Muscle spasms
Adult: As orphenadrine citrate: 60 mg every 12 hr by IM or slow IV inj.
Administration
May be taken with or without food. May be taken w/ meals if GI upset occurs.
Contraindications
Prostatic hypertrophy, tardive dyskinesia, porphyria, urinary retention, paralytic ileus, pyloric stenosis, glaucoma, risk of developing hyperpyrexia, cardiospasm, and myasthenia gravis.
Special Precautions
Patient w/ conditions characterized by tachycardia (e.g heart failure, thyrotoxicosis); cardiac arrhythmias, HTN, cardiac impairment, coronary insufficiency, micturition difficulties, history of drug abuse, acute alcoholism. Avoid abrupt withdrawal. Renal and hepatic impairment. Pregnancy and lactation. Patient Counselling This drug may cause dizziness, drowsiness, slight euphoria or blurred vision, if affected, do not drive or operate machineries.
Adverse Reactions
Significant: CNS depression, tachycardia, euphoria, potential for abuse, increased intraocular pressure, GI obstruction, skeletal muscle pain/spasm. Nervous: Dizziness, drowsiness, restlessness, sedation, confusion, nervousness, hallucinations, convulsions, insomnia, coordination disturbances, light-headedness, headache, agitation, tremor, weakness. CV: Palpitation. GI: Dry mouth, nausea, vomiting, GI disturbances, constipation, gastric irritation. Resp: Nasal congestion. Genitourinary: Urinary retention/hesitancy. Ophthalmologic: Accommodation disorders, blurred vision, nystagmus, dilatation of pupils. Dermatologic: Pruritus, urticaria.
Overdosage
Symptoms: Nausea, vomiting, flushing, dilated pupils, dry mouth and tongue, hot dry skin, fever, sinus tachycardia, HTN, ataxia, nystagmus, drowsiness, delirium, agitation and visual hallucinations. Management: Supportive treatment. Administer activated charcoal or gastric lavage w/in 1 hr of ingestion. Establish patent airway and provide oxygen or ventilation to correct hypoxia or hypercapnoea. Monitor body temp. Convulsions or delirium can be treated w/diazepam. Maintain BP, may give intravascular vol expanders, adrenaline, dopamine, dobutamine if necessary. Administer Na bicarbonate for cardiac dysrhythmias.
Drug Interactions
Increased anti-muscarinic effects (e.g. risk of severe constipation, ileus, atropine-like psychoses and heat stroke) w/ anticholinergic drugs, antihistamines, antispasmodics, tricyclic antidepressants, phenothiazines, dopaminergic anti-parkinsonian drugs (e.g. amantadine) and anti-arrhythmics (e.g. disopyramide). May cause confusion, anxiety and tremors w/ propoxyphene. May cause skeletal muscle spasms/pain w/ analgesics.
Action
Orphenadrine is a tertiary amine antimuscarinic which exerts antiparkinsonian action by inhibiting excess central cholinergic effects that occur due to dopamine deficiency. It reduces muscle spasms possibly by its atropine-like effect on the medulla or on cerebral motor centers.
Onset: 2-4 hr (oral).
Duration: Reduction of muscle spasms: 4-6 hr.
Absorption: Readily absorbed from the GI tract.
Distribution: Plasma protein binding: 20%.
Metabolism: Almost completely metabolised in the liver into at least 8 metabolites.
Excretion: Via urine (as metabolites, 8% as unchanged drug). Elimination half-life: 14-16 hr.
Storage
Oral: Store between 20-25°C. Parenteral: Store between 20-25°C.
Disclaimer: This information is independently developed by CIMS based on orphenadrine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to CIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, CIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 CIMS. All rights reserved. Powered by CIMSAsia.com
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