Prolonged hypotension induced by ingesting a topical minoxidil solution: analysis of minoxidil and its metabolites.

CASE

A 47-year-old man ingested 60 mL of a topical solution (3,000 mg minoxidil) and presented with prolonged hypotension. Treatment with dopamine hydrochloride and noradrenaline provided blood pressure control. Serum unchanged minoxidil concentrations at 4 and 16 h after ingestion were 4,994 and 33.9 ng/mL, respectively. Urine concentrations of unchanged minoxidil, minoxidil--glucuronide, and minoxidil---sulfate at 16 h after ingestion were 360.4, 1,953, and 104.5 ng/mL, respectively.

OUTCOME

The serum unchanged minoxidil concentration rapidly decreased over a short interval. However, the patient needed to receive vasopressor support for the first 4 days after being admitted to the hospital. The urine minoxidil--glucuronide concentration was higher than the concentrations of unchanged minoxidil and minoxidil---sulfate.

CONCLUSION

Although the serum concentration of unchanged minoxidil rapidly decreased, ingesting large amounts of a topical minoxidil solution can have serious and prolonged cardiovascular effects. Analyzing the minoxidil--glucuronide concentration in urine is useful for diagnosing minoxidil poisoning.