From the Guidelines
Minoxidil overdose symptoms typically begin within minutes to hours after excessive exposure, with peak activity generally occurring within 2-4 hours after overdose. For topical minoxidil, symptoms may appear within 30-60 minutes of application, while oral minoxidil overdose effects can begin within 1-2 hours of ingestion 1. The primary concern with minoxidil overdose is severe hypotension (low blood pressure) due to its potent vasodilatory effects, which can lead to reflex tachycardia, dizziness, flushing, headache, and in severe cases, cardiovascular collapse.
Some key points to consider in the management of minoxidil overdose include:
- The use of minoxidil is associated with hirsutism and requires a loop diuretic, and it can also induce pericardial effusion 1
- Minoxidil is a direct vasodilator, and its overdose can lead to severe hypotension, which can be life-threatening if not managed promptly and properly
- The severity and duration of symptoms depend on the amount ingested or applied, the formulation (oral versus topical), and individual factors such as age and underlying health conditions
Given the potential for severe hypotension and other complications, it is essential to seek immediate medical attention if symptoms of minoxidil overdose occur, as treatment may require intensive monitoring, intravenous fluids, vasopressors, and possibly dialysis in severe cases 1.
From the Research
Minoxidil Overdose Onset of Action and Peak Activity
- The onset of action for minoxidil overdose can occur within 2 hours of ingestion, with symptoms including tachycardia, hypotension, and decreased systemic vascular resistance 2.
- In one case, a young girl who ingested 100 mg of topical minoxidil had no symptoms except for flush on the face and ears initially, but developed tachycardia and hypotension 4.5 hours after ingestion 3.
- The peak activity of minoxidil overdose can last for several hours to days, with one patient experiencing tachycardia for 40 hours 3 and another patient requiring dopamine for 2 days to maintain blood pressure 2.
- The severity and duration of toxicity can be profound, with patients requiring vasopressor support, intubation, and prolonged therapy with furosemide 4.
- Minoxidil's effect can be limited by an increase in pulse rate and/or sodium (and water) retention, which can be debilitating in some patients 5.
Symptoms and Treatment
- Symptoms of minoxidil overdose can include severe hypotension, tachycardia, and decreased systemic vascular resistance 6, 2, 4.
- Treatment for minoxidil overdose typically involves administration of crystalloid solution, dopamine, and/or phenylephrine to manage hypotension and tachycardia 6, 2, 4.
- Patients may also require prolonged medical supervision due to the product's very long action 3.