To the Editor:
We would like to comment on the recently published case report by Lin and colleagues entitled “Myoclonic jerks due to acute bromovalerylurea intoxication.”Citation1 The authors describe a patient who had ingested an acutely toxic dose of the bromide-containing hypnotic-sedative bromovalerylurea and presented at the Emergency Department with myoclonic jerks. Blood bromide levels were remarkably low, reported to be 81.0 mg/L. As the author correctly stated, blood bromism generally occurs when patients have blood bromine levels in excess of 500 mg/L. Commenting on their patient's low halide concentration, Lin and colleagues suggest acute bromism may differ from chronic toxicity and cite papers associated with methyl bromide intoxication resulting in similarly elevated bromide blood levels to what was reported for the bromovalerylurea overdose patient.
Unfortunately, these authors have confused bromism with methyl bromide intoxication, they are two separate and distinct toxodromes. The intact methyl bromide molecule acts directly as an alkylating agent on amino acids and bioactive proteins that contain sulfhydryl groups, leading to a permanent cytotoxic effect.Citation2 In contrast, bromide ions temporarily displace chlorine ions in neuronal cells that can lead to impaired neurotransmission.Citation3 Furthermore, blood bromide levels cannot be correlated with severity of methyl bromide symptoms. Deaths have occurred with patients with blood bromide levels as low as 83 mg/L,Citation4 whereas others suffered only dizziness at 125 mg/L.Citation5 Comparing bromism with methyl bromide toxicity is therefore not valid and an alternate hypothesis must be considered to explain the anomaly between low bromide levels and reported neurological symptoms.
References
- Lin JN, Lin HL, Huang CK, Lai CH, Chung HC, Liang SH, Lin HH. Myoclonic jerks due to acute bromovalerylurea intoxication. Clin Toxicol 2008; 46:861–863.
- Nishimura M, Umeda M, Ishizu S, Sato M. Cytotoxicity of methyl bromide: effect of methyl bromide on cultured mammalian cells. J Toxicol Sci 1980; 5:321–330.
- James LP, Farrar HC, Griebel ML, Bates SR. Bromism: intoxication from a rare anticonvulsant therapy. Pediatr Emerg Care 1997; 13:268–270.
- Clarke CA, Roworth CG, Holling HE. Methyl bromide poisoning – an account of 4 recent cases met within 1 of HM ships. Br J Ind Med 1945; 2:17–23.
- Benatt AJ, Courtney TRB. Uraemia in methyl bromide poisoning – a case report. Br J Ind Med 1948; 5:21–25.