TRANCOPAL
Clinical safety rating
cautionComprehensive clinical and safety monograph for TRANCOPAL (TRANCOPAL).
Trancopal (chlormezanone) is a centrally acting muscle relaxant and anxiolytic. Its exact mechanism is not fully understood, but it is believed to act on the central nervous system by depressing polysynaptic reflexes and possibly through GABAergic modulation.
| Metabolism | Hepatic metabolism; primarily via oxidation and conjugation; exact enzymes not well characterized. |
| Excretion | Primarily renal: ~95% as metabolites (glucuronides, sulfate conjugates) with <1% unchanged. Fecal: <5%. |
| Half-life | Terminal elimination half-life: 20-30 hours in healthy adults. Prolonged in hepatic impairment (up to 60 hours). |
| Protein binding | ~99% bound primarily to albumin; minimal binding to α1-acid glycoprotein. |
| Volume of Distribution | 0.2-0.3 L/kg, indicating limited distribution primarily to extracellular fluid and well-perfused tissues. |
| Bioavailability | Oral bioavailability ~25% due to extensive first-pass hepatic metabolism (high extraction ratio). |
| Onset of Action | Oral: 30 minutes after single dose. Peak effect: 2-3 hours. |
| Duration of Action | 4-6 hours for analgesic effect; muscle relaxation persists up to 8 hours. Duration may be extended in elderly or hepatic dysfunction. |
| Molecular Weight | 410.31 |
200-400 mg orally every 6 hours as needed for acute musculoskeletal pain; maximum 1.6 g per day.
| Dosage form | TABLET |
| Renal impairment | GFR <30 mL/min: avoid use. GFR 30-50 mL/min: reduce dose by 50% or extend interval. Not studied in severe impairment. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated. |
| Pediatric use | Not recommended for use in children under 16 years due to lack of safety and efficacy data. |
| Geriatric use | Start at lower end of dosing range; 200 mg orally every 8-12 hours. Caution due to increased risk of sedation and falls. |
| 1st trimester | Avoid use during first trimester due to potential teratogenic effects; limited human data show possible association with congenital malformations. |
| 2nd trimester | Use only if clearly needed; no well-controlled studies, but animal studies have shown adverse effects. |
| 3rd trimester | Avoid use during third trimester, especially near term, as may cause neonatal respiratory depression and withdrawal symptoms. |
Clinical note
Comprehensive clinical and safety monograph for TRANCOPAL (TRANCOPAL).
| Placental transfer | Chlorzoxazone (active metabolite) crosses the placenta; limited data suggest transfer is moderate. |
| Breastfeeding | Excreted into breast milk in small amounts; unlikely to cause adverse effects in infant, but caution is advised; monitor infant for sedation and feeding difficulties. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Trancopal (chlormezanone) is a centrally acting muscle relaxant. Studies in animals have shown teratogenic effects. During the first trimester, there is a risk of congenital malformations, particularly neural tube defects, based on limited human data. In the second and third trimesters, potential risks include fetal growth restriction and altered fetal muscle tone. The drug should be avoided throughout pregnancy unless benefits clearly outweigh risks. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate regularly due to possible hypotensive effects. Fetal monitoring includes ultrasound assessment of growth and amniotic fluid volume during prolonged use. Assess neonatal muscle tone and respiratory status postpartum if drug used near delivery. Liver function tests may be warranted due to rare hepatotoxicity. |
| Fertility Effects | Limited data exist on human fertility. Animal studies have not shown significant effects on fertility. Theoretical concerns include hormonal interference at high doses. No specific impairment in male or female fertility has been documented. Consider alternative agents if planning pregnancy. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to chlorzoxazone or any componentConcurrent use with alcohol or other CNS depressantsSevere hepatic impairment
| Precautions | May cause drowsiness, dizziness, or blurred vision; caution in patients requiring mental alertness, Avoid concurrent use with alcohol or other CNS depressants, Use with caution in patients with hepatic or renal impairment, May be habit-forming; potential for dependence with prolonged use |
| Food/Dietary | No specific food interactions reported. However, avoid alcohol as it potentiates CNS depression. |
| Clinical Pearls | Trancopal (chlormezanone) is a centrally acting muscle relaxant and anxiolytic. Due to risk of severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome), it has been withdrawn in many countries. Not recommended for first-line use. Monitor for sedation and avoid combining with other CNS depressants. |
| Patient Advice | Avoid alcohol and other CNS depressants as they increase drowsiness and dizziness. · Do not drive or operate heavy machinery until you know how this medication affects you. · Seek immediate medical attention if you develop rash, blisters, or signs of an allergic reaction. · Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Do not stop abruptly; gradual taper may be needed to avoid withdrawal symptoms. |
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