TOXICOLOGY■ Folate:Improves the metabolism of formic acid.
■ Urinary alkalinization: Improves renal clearance of formic acid.
■ Considerhemodialysisin cases of severe acidosis, visual changes or a
serum level >50 mg/dL; effectively removes both the parent compound
and formic acid.
COMPLICATIONS
■ Permanent visual losses and parkinsonian motor dysfunction may occur.
Ethylene Glycol
Ethylene glycol is mostly available in engine coolants (antifreeze). It is
ingested under similar circumstances as methanol.
MECHANISM/TOXICITY
■ Ethylene glycol itself has minimal toxicity: It causes mild intoxication.
■ Metabolized by ADH to a toxic metabolite, oxalic acid
■ Oxalic acid accumulation →anion gap metabolic acidosis and direct
renal toxicity.
SYMPTOMS/EXAM
■ Intoxication, headache, CNS depression, cranial neuropathy (delayed)
■ Abdominal pain, N/V
■ Acute renal failure
DIAGNOSIS
■ Gold standard is direct serum measurement.
■ Suspect ethylene glycol ingestion if patient has an osmolal gap, anion gap
metabolic acidosis and acute renal failure.
■ Presence of oxalate crystals in the urine(suggestive of diagnosis, but is
not sensitive or specific)
■ Some brands of antifreeze contain fluorescent dyes to aid in the identifica-
tion of coolant leaks and will fluoresce under Woods lamp (UV light);
however, the practice of examining a patient’s urine under UV light is
highly unreliable and should not be used to confirm or rule out ingestion.
TREATMENT
■ Antidote = fomepizoleorethanol.
■ Blocks ADH, preventing production of formic acid
■ Thiamineandpyridoxine(vitamin B 6 ) may help convert oxalic acid to
nontoxic metabolites.
■ Considerhemodialysisin cases of severe acidosis (pH <7.3), renal failure
or a serum level >50 mg/dL.
COMPLICATIONS
■ Renal damage may be irreversible in severe poisonings.
Isopropanol (Isopropyl Alcohol)
Isopropanol is found in rubbing alcohol and some hand sanitizers. It is most
often ingested as an ethanol substitute. Intoxication due to isopropanol is
more severe than that due to an equivalent amount of ethanol.
Urinary alkalinization is used
to increase renal clearance of
formic acid.Intoxicated patient with
osmolal gap, anion gap
metabolic acidosis, and acute
renal failure = ethylene glycol.Antidote to methanol and
ethylene glycol poisoning =
fomepizole or ethanol.