Your dad wanted to make this holiday season extra special, so he decided to paint the house in candy-cane pattern. The intermittent red and white stripes were so disorienting, that he mistook his paint thinner for his nalgene, and took a big swig of water. Oops! He arrives in your ED covered in red and white paint, looking to be in bad shape. He doesn’t even recognize you! What’s going on, why, and what do we do to save dad?!
Paint thinner, along with anti-freeze, windshield wiper fluid, shellac, copy machine fluids, canned heating sources, fuel additives (octane boosters), and varnish contain methanol. After ingestion, methanol is quickly metabolized to formaldehyde and subsequently oxidized to formic acid (see flow chart below). Thus, even though methanol itself is non-toxic, its metabolite, formic acid is, and causes severe anion-gap metabolic acidosis, optic neuropathy and putaminal hemorrhage/necrosis. The latter is often described as a “snowy” field of vision – no wonder dad doesn’t recognize you! Is a swig pf paint thinner enough to cause toxicity? In fact, it is. As little as 4 mLs of methanol can cause ocular findings, including blindness and and as little as 30 to 60 mLs can be lethal. A more common lethal dose would be 70 to 100 mLs.
Treatment is either PO or (if cannot take PO) IV ethanol or fomepizole, both of which block degradation of methanol into its toxic metabolites (see chart). Mom, however, does not like the idea of giving dad a fifth of vodka, so you opt for IV fomepizole, which you give as a loading dose of 15 mg/kg, followed by doses of 10 mg/kg every 12 hours for 4 doses, then 15 mg/kg every 12 hours thereafter until toxin levels have been reduced <20 mg/dL and dad is asymptomatic with normal pH.
In order to break down the already formed formic acid, you need to administer folinic acid, an essential co-factor for the metabolism of formic acid.
Goldfrank LR, ed. Goldfrank’s Toxicologic Emergencies . 9th ed. New York, NY: McGraw Hill; 2011.
White SR. Toxic Alcohols, in Marx JA, Hockberger RS, Walls RM, et al (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, ed 8. St. Louis, Mosby, Inc., 2013, (Ch) 155: p 2007-2015
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