Paracetamol, orphenadrine citrate.
White to off-white round tablet, biconvex, plain on both sides.
Each tablet contains: Paracetamol 450 mg, Orphenadrine Citrate 35 mg.
Pharmacology: Pharmacodynamics: Paracetamol, a para-aminophenol derivative, is a peripherally acting analgesic with antipyretic and weak anti-inflammatory activity. Orphenadrine, an analog of diphenhydramine, is a skeletal muscle relaxant and is postulated to act on cerebral motor center or on the medulla through an atropine-like central action. It has anticholinergic, local anaesthetic effects and some antihistaminic effects.
Orphenadrine is used either as the hydrochloride or the citrate and doses are expressed in terms of the relevant salt.
Pharmacokinetics: Absorption: Paracetamol: Absorbed readily from GI tract; time to peak plasma concentrations: 10-60 minutes.
Orphenadrine: Absorbed readily from GI tract and after IM injection.
Distribution: Paracetamol: Distributed into most body tissues including breast milk, crosses the placenta; plasma-protein binding: negligible (but dose dependent).
Orphenadrine: May cross placenta.
Metabolism: Paracetamol: Undergoes hepatic metabolism; a minor metabolite, produced in minute amounts by cytochrome P450 isoenzymes in the liver and kidney, is usually removed by conjugation with glutathione, but may accumulate and cause tissue damage in paracetamol overdosage.
Orphenadrine: Metabolised to ≥8 metabolites.
Excretion: Paracetamol: Excreted in the urine mainly as the glucuronide and sulfate conjugates with <5% excreted unchanged; elimination half-life: 1-3 hrs.
Orphenadrine: Excreted mainly in urine and unchanged drug (small amounts); half-life: 14 hrs.
It is used for acute or chronic painful muscular conditions, non-articular rheumatism, whiplash injury, acute torticollis, tension headache, dysmenorrhea.
1-2 tablets 3 times a day or as directed. May be taken with meals if GI upset occurs.
Paracetamol: Symptoms: Paleness, nausea, vomiting, anorexia, abdominal pain, metabolic acidosis and glucose metabolism disturbances. Liver damage may surface 12-48 hrs. after overdose. In severe cases, encephalopathy, haemorrhage, hypoglycaemia, cerebral oedema, acute renal failure and death.
Management: Immediate medical treatment even if there are no symptoms. If presented within 1 hr of poisoning, administration of activated charcoal. If needed, administration of N-acetylcysteine or oral methionine.
Orphenadrine: Symptoms: Vomiting, gastric irritation, dilated pupils, pruritus, urinary retention, tachycardia, hyperpyrexia, euphoria, hallucinations, agitation, paranoid reactions, tremor, excitement, confusion, delirium, circulatory and respiratory failure, coma and convulsions.
Management: Treatment is symptomatic and supportive.
Contraindications result from the parasympatholytic action of Orphenadrine. Should not be given to patients with glaucoma, prostatic hypertrophy, obstruction at the bladder, neck or myasthenia gravis. Should be used with caution in patients with tachycardia.
Impaired kidney or liver function, or in patients with cardiac failure, coronary insufficiency, cardiac arrhythmias and tachycardia. Alcohol dependence. Pregnancy and lactation. In prolonged therapy, monitor blood, urine, and LFTs periodically. May affect ability to drive or operate machinery.
Use in Pregnancy: Not recommended for use during pregnancy.
Use in Lactation: Should not be taken during lactation as paracetamol and orphenadrine are excreted into breast milk.
Dry mouth, nausea, blurring of vision, dizziness and restlessness may occur in some patients susceptible to the parasympatholytic action of Orphenadrine. These symptoms disappear rapidly following reduction of dosage or withdrawal of treatment.
Increased paracetamol absorption with metoclopramide and domperidone. Decreased paracetamol absorption with cholestyramine. May increase risk of bleeding with warfarin and coumarins. Increased anticholinergic side effects with other anticholinergic drugs. Additive CNS effects with propoxyphene. Increased bupropion levels with concurrent use.
May antagonise actions of centrally acting anticholinesterases e.g. donepezil, galantamine, rivastigmine, tacrine. May decrease levodopa absorption with concurrent use.
Potentially Fatal: Increased risk of liver damage with alcohol.
Store at temperatures not exceeding 30°C.
M03BC51 - orphenadrine, combinations ; Belongs to the class of ethers. Used as centrally-acting muscle relaxants.
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