Experience with doxazosin mesylate overdosage is limited. Two adolescents who each intentionally ingested 40 mg doxazosin mesylate with diclofenac or acetaminophen, were treated with gastric lavage with activated charcoal and made full recoveries. A two-year-old child who accidentally ingested 4 mg doxazosin mesylate was treated with gastric lavage and remained normotensive during the five-hour emergency room observation period. A six-month-old child accidentally received a crushed 1 mg tablet of doxazosin mesylate and was reported to have been drowsy. A 32-year-old female with chronic renal failure, epilepsy and depression intentionally ingested 60 mg doxazosin mesylate (blood level 0.9 mcg/ml; normal values in hypertensives=0.02 mcg/ml); death was attributed to a grand mal seizure resulting from hypotension. A 39-year-old female who ingested 70 mg doxazosin mesylate, alcohol and Dalmane (flurazepam) developed hypotension which responded to fluid therapy.

The oral LD₅₀ of doxazosin is greater than 1000 mg/kg in mice and rats. The most likely manifestation of overdosage would be hypotension, for which the usual treatment would be intravenous infusion of fluid. As doxazosin is highly protein bound, dialysis would not be indicated.

Doxazosin mesylate is contraindicated in patients with a known sensitivity to quinazolines (e.g., prazosin, terazosin) or any of the inert ingredients.

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