chlorzoxazone (Parafon, Parafon-Forte)

Introduction

Tradenames: Parafon, Forte.

Indications

muscle relaxant

Dosage

250-500 mg PO TID/QID, max 750 mg QID

Tabs: 250 & 500 mg.

Pharmacokinetics

• effects last 3-4 hours
• < 1% of drug is excreted unchanged in the urine

elimination via liver

elimination via kidney

Adverse effects

(drug well tolerated by most patients)

• nausea
• dyspepsia
• dizziness
• drowsiness
• discoloration of urine
• hepatotoxicity: discontinue use
• rash or itching: discontinue use

Laboratory

• chlorzoxazone in serum/plasma
• chlorzoxazone in urine

Mechanism of action

• centrally-acting muscle relaxant
• acts primarily at the spinal cord & subcortical areas of brain
• inhibits multisynaptic reflex arcs involved in producing & maintaining skeletal muscle spasm
• does not directly relax tense skeletal muscles

More general terms

• skeletal muscle relaxant (tranquilizer)

Component of

• acetaminophen/chlorzoxazone

Database

• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=2733