Chlorzoxazone overdose
1
Reactions 718 - 12 Sep 1998 S Chlorzoxazone overdose Coma: case report Coma occurred in a 57-year-old man on 2 separate occasions after he took overdoses of chlorzoxazone [‘Parafon Forte’]. The man’s medications included disulfiram, oxazepam, phenobarbital and chlorzoxazone. On the first occasion, he was found in a somnolent state with slurred speech. On arrival at an emergency department, he became comatose for 12 hours and required intubation and mechanical ventilation. He was extubated after 24 hours and recovered uneventfully. On admission, his phenobarbital concentration was sub- therapeutic and his nordiazepam concentration was low. He reported taking 7 chlorzoxazone tablets (3.5g) over a 2-hour period for back spasms. On the second occasion, the man was found in a somnolent, confused state and, when paramedics arrived, he was comatose. Treatment with naloxone was unsuccessful. Following treatment with IV flumazenil, he awoke in a confused state, and then became comatose again. Following a second dose of the agent, he awoke, and was conversant. He reported taking a ‘handful’ of chlorzoxazone pills approximately 4 hours before admission; his chlorzoxazone concentration was 39 µg/ml. Author comment: Despite the possibility of synergistic depressant effects from the other drugs involved, the subtherapeutic phenobarbital and low-therapeutic benzodiazepine concentrations at the first admission suggest that chlorzoxazone was the major depressive agent. Chlorzoxazone should not be given with concomitant disulfiram because inhibition of the specific metabolic catalyst for chlorzoxazone can lead to increased serum levels and toxicity. ‘Flumazenil may be a useful antidote for CZX [chlorzoxazone] toxicity, but further experience will be required to more clearly delineate its ultimate role.’ Roberge RJ, et al. Two chlorzoxazone (Parafon Forte) overdoses and coma in one patient: reveral with flumazenil. American Journal of Emergency Medicine 16: 393-395, Jul 1998 - USA 800693457 1 Reactions 12 Sep 1998 No. 718 0114-9954/10/0718-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved
Transcript of Chlorzoxazone overdose
Reactions 718 - 12 Sep 1998
SChlorzoxazone overdose
Coma: case reportComa occurred in a 57-year-old man on 2 separate
occasions after he took overdoses of chlorzoxazone [‘ParafonForte’].
The man’s medications included disulfiram, oxazepam,phenobarbital and chlorzoxazone. On the first occasion, hewas found in a somnolent state with slurred speech. On arrivalat an emergency department, he became comatose for 12hours and required intubation and mechanical ventilation. Hewas extubated after 24 hours and recovered uneventfully. Onadmission, his phenobarbital concentration was sub-therapeutic and his nordiazepam concentration was low. Hereported taking 7 chlorzoxazone tablets (3.5g) over a 2-hourperiod for back spasms.
On the second occasion, the man was found in a somnolent,confused state and, when paramedics arrived, he wascomatose. Treatment with naloxone was unsuccessful.Following treatment with IV flumazenil, he awoke in aconfused state, and then became comatose again. Following asecond dose of the agent, he awoke, and was conversant. Hereported taking a ‘handful’ of chlorzoxazone pillsapproximately 4 hours before admission; his chlorzoxazoneconcentration was 39 µg/ml.
Author comment: Despite the possibility of synergisticdepressant effects from the other drugs involved, thesubtherapeutic phenobarbital and low-therapeuticbenzodiazepine concentrations at the first admission suggestthat chlorzoxazone was the major depressive agent.Chlorzoxazone should not be given with concomitantdisulfiram because inhibition of the specific metabolic catalystfor chlorzoxazone can lead to increased serum levels andtoxicity. ‘Flumazenil may be a useful antidote for CZX[chlorzoxazone] toxicity, but further experience will berequired to more clearly delineate its ultimate role.’Roberge RJ, et al. Two chlorzoxazone (Parafon Forte) overdoses and coma in onepatient: reveral with flumazenil. American Journal of Emergency Medicine 16:393-395, Jul 1998 - USA 800693457
1
Reactions 12 Sep 1998 No. 7180114-9954/10/0718-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved
