There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the FDA Drug Label
Experience with doxazosin overdosage is limited. Two adolescents, who each intentionally ingested 40 mg doxazosin with diclofenac or acetaminophen, were treated with gastric lavage with activated charcoal and made full recoveries A two-year-old child who accidently ingested 4 mg doxazosin 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 and was reported to have been drowsy A 32-year-old female with chronic renal failure, epilepsy, and depression intentionally ingested 60 mg doxazosin (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, alcohol, and Dalmane ® (flurazepam) developed hypotension which responded to fluid therapy. The oral LD 50 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.
The effects of an overdose of doxazosin may include:
- Hypotension: the most likely manifestation of overdosage
- Drowsiness: reported in a six-month-old child who accidentally received a crushed 1 mg tablet of doxazosin
- Grand mal seizure: attributed to hypotension in a 32-year-old female who intentionally ingested 60 mg doxazosin 1 Treatment for overdosage would likely involve intravenous infusion of fluid to manage hypotension.
From the Research
Effects of Doxazosin Overdose
- The effects of an overdose of doxazosin are not extensively documented in the provided studies, but one case report is mentioned in the study published in 2005 2.
- According to this study, a patient who overdosed on doxazosin was given supportive treatment and discharged 48 hours after admission to the emergency department 2.
- The other studies provided focus on the antihypertensive effects, pharmacokinetics, and therapeutic applications of doxazosin in hypertension and benign prostatic hyperplasia, but do not discuss overdose effects in detail 3, 4, 5, 6.
- The study published in 1988 4 reports on the antihypertensive effects and steady-state pharmacokinetics of doxazosin, but does not mention overdose.
- The studies published in 2008 3 and 1995 5 discuss the clinical pharmacology and therapeutic applications of doxazosin, but do not provide information on overdose effects.
- The study published in 1988 6 reviews the pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy of doxazosin in mild or moderate hypertension, but does not mention overdose.