RESUMEN
BACKGROUND: Relying on a treatment threshold for methanol poisoning of 20 mg/dL (6.2 mmol/L) as a stand-alone criterion may lead to unnecessary and invasive treatment because it is likely too conservative, especially for patients with repeated, intentional methanol exposures. OBJECTIVE: We investigated how often patients with recurrent intentional methanol exposures above this threshold developed biochemical or overt clinical toxicity despite not being treated with either an alcohol dehydrogenase inhibitor (ADHi) or hemodialysis. METHODS: We identified patients with ≥3 methanol-related emergency visits from 2002 to 2015 and selected every visit in which neither ADHi nor hemodialysis were administered despite serum methanol >20 mg/dL but neither metabolic acidosis nor end organ toxicity at presentation. The primary outcome was the incidence of visual deterioration or death. RESULTS: Four patients accounted for the 17 visits that met inclusion criteria. All exposures were intentional substance misuse, and 7 of 17 were via inhalation (i.e., huffing). Initial methanol concentrations ranged from 22 mg/dL to 35 mg/dL (7-11 mmol/L). Four of these 17 visits had undetectable initial ethanol concentrations at presentation, including 1 with an initial methanol concentration of 35 mg/dL. No patients developed visual deterioration, and all were known to have survived the exposure. CONCLUSION: Following recurrent, intentional methanol exposure, isolated serum methanol concentrations as high as 35 mg/dL (11 mmol/L) appear to be well-tolerated without treatment in the absence of metabolic acidosis or end-organ toxicity. To better define the methanol treatment threshold, prospective studies are warranted in which patients are followed closely while fomepizole is withheld.