Severe hepatocellular damage induced by chlormezanone overdose.

Chlormezanone is a widely prescribed muscle relaxant (1-3) whose pharmacology is well known (4-6), but the clinical effect of overdose still remains relatively obscure (1, 7, 8). We here report a recent case of a patient who had severe liver function impairment and other associated findings typical of chlormezanone overdose. The ingested dose (at least 12 g) is much larger than those of previous record (1, 2, 7, 8); thus, her critical presentation deserves to be reviewed.

Chlormezanone plasma and blood levels in patients after single and repeated oral doses and after suicidal drug overdose.

Chlormezanone plasma concentrations were determined in 5 volunteers (group 1) after a single oral dose of 200 mg of chlormezanone with high performance liquid chromatography. A plasma elimination half-life of 23 +/- 2.3 h was calculated. The mean peak chlormezanone plasma level was 1.86 +/- 0.2 micrograms/ml, 1 h after ingestion. Additionally, chlormezanone plasma levels were determined after repeated oral doses of chlormezanone recommended for treatment of muscular spasms due to degenerative skeletal disease. After 5 days of repeated daily doses of 3 x 200 mg (group 2; 12 patients) or 3 x 400 mg (group 3; 10 patients) of chlormezanone, mean predose chlormezanone plasma levels were 12.0 +/- 2.0 micrograms/ml (group 2) and 22.7 +/- 4.0 micrograms/ml (group 3), respectively. Comparable plasma concentrations were determined after 10 days of repeated doses of 3 x 200 mg or 3 x 400 mg of chlormezanone in 3 patients from each of these 2 groups. In 7 patients of group 3, chlormezanone had to be discontinued on the 5th day due to increasing muscular weakness, ataxia and exercise-inducible tachycardia. After a loading dose of 800 mg and repeated doses of 3 x 200 mg chlormezanone to 5 patients (group 4), plasma levels of 6.5 +/- 2.1 micrograms/ml, 8.9 +/- 2.2 micrograms/ml, 12.7 +/- 2.0 micrograms/ml, and 10.4 +/- 2.4 micrograms/ml were determined after 2, 8, 16, and 36 h, respectively. Trace amounts of a degradation product of the acid-labile chlormezanone could be detected in plasma besides the unchanged drug after administration of repeated oral doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Central anticholinergic syndrome after ofloxacin overdose and therapeutic doses of diphenhydramine and chlormezanone.

A 14-year-old female with no history of psychiatric disease ingested an unknown amount of ofloxacin, diphenhydramine and chlormezanone after an argument with her patients. Approximately 12 hours after ingestion, the patient was admitted to the hospital in a delirious state with extreme mydriasis and warm and dry skin. Analytical data on admission were consistent with ofloxacin overdose and ingestion of therapeutic doses of diphenhydramine and chlormezanone. The patient received activated charcoal and forced diuresis was instituted. Psychosis and anticholinergic symptoms lasted in the next 2 days. On day 3, the psychotic and anticholinergic symptoms were nearly completely reversed by 2 mg physostigmine salicylate, given IV x 2. Since anticholinergic symptoms have not been observed after ofloxacin overdose or after therapeutic doses of diphenhydramine or chlormezanone, this case suggests a potentiation of the anticholinergic effects of diphenhydramine and chlormezanone by ofloxacin overdose.