Dosing and uses of Parafon Forte DSC, Lorzone (chlorzoxazone)
Adult dosage forms and strengths
tablet
- 375mg
- 500mg
- 750mg
Musculoskeletal Conditions
250-750 mg PO q6-8hr
Pediatric dosage forms and strengths
tablet
- 375mg
- 500mg
- 750mg
Muscle Spasms
20 mg/kg/day PO divided q6-8hr or 600 mg/m²/day PO divided q6-8hr
Geriatric dosage forms and strengths
Musculoskeletal Conditions
250 mg PO q6-12hr; increase PRN to 750 mg PO q6-8hr
Parafon Forte DSC, Lorzone (chlorzoxazone) adverse (side) effects
1-10%
Lightheadedness
Dizziness
Drowsiness
Excitement, ParadoxicaL
Somnolence
Malaise
Rash
Angioneurotic edema
<1%
Gastrointestinal hemorrhage (rare)
Hepatotoxicity (rare)
Anaphylaxis (rare)
Warnings
Contraindications
Hypersensitivity
Impaired liver function
Cautions
May cause drowsiness/dizziness
May take with food to avoid stomach upset
Poor tolerance by the elderly
Pregnancy and lactation
Pregnancy category: C
Lactation: not known if excreted in breast milk
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Parafon Forte DSC, Lorzone (chlorzoxazone)
Mechanism of action
Blocks interneuronal conduction in spinal cord and subcortical brain areas by depressing polysynaptic reflexes
Pharmacokinetics
Half-life: 66 min
Onset: 1 hr
Duration: 6-12 hr
Peak Plasma Time: 1-4 hr
Peak Plasm Concentration: 9-20 mcg/mL
Metabolism: Rapid hepatic glucuronidation
Metabolites: 6-hydroxychlorzoxazone (inactive; rapidly excreted in urine)
Excretion: Urine (primarily)