[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Direct vasodilators](https://durgical.com/en/pharmacology/classes/direct-vasodilators/) › Minoxidil

[Pharmacology](https://durgical.com/en/pharmacology/) · [Direct vasodilators](https://durgical.com/en/pharmacology/classes/direct-vasodilators/)

# Minoxidil

A powerful oral vasodilator kept for severe, resistant hypertension. It is given with a beta blocker and a diuretic, and it makes body hair grow.

Updated 2026-11-01

- Class: [Direct vasodilators](https://durgical.com/en/pharmacology/classes/direct-vasodilators/)
- Ion channel: ATP-sensitive potassium channel of vascular smooth muscle (SUR2 subunit)
- ATC code: C02DC01

## Mechanism of action

Minoxidil is a prodrug: its sulfate metabolite opens ATP-sensitive potassium channels in arteriolar smooth muscle. Potassium leaves the cell, the membrane hyperpolarises, calcium entry falls and the arterioles relax; veins are hardly affected. The large fall in resistance triggers reflex tachycardia, higher cardiac output and strong salt and water retention.

- Minoxidil is sulfated to its active form
- Minoxidil sulfate opens ATP-sensitive potassium channels
- Arteriolar muscle hyperpolarises and relaxes
- Reflex tachycardia and fluid retention follow

## Pharmacokinetics

**Absorption**
At least 90 percent absorbed from the gut (label)

**Metabolism**
Mostly metabolised, mainly by glucuronidation; the active form is minoxidil sulfate

**Elimination**
Metabolites leave mainly in urine; removed by haemodialysis

**Half-life**
Plasma half-life about 4.2 hours (label); the effect lasts much longer

## Indications

- Severe hypertension that is symptomatic or damages organs and is not controlled by a diuretic plus two other antihypertensives [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/)
- Other form: topical minoxidil for androgenetic alopecia

## Adverse effects

### Common

- Hypertrichosis: longer, thicker, darker body hair
- Tachycardia
- Salt and water retention with oedema and weight gain
- Headache and sweating

### Serious (rare, important)

- Pericardial effusion, sometimes progressing to tamponade
- Worsening or new angina
- Heart failure from fluid retention

## Contraindications

- Pheochromocytoma
- Hypersensitivity to minoxidil

## Key interactions

**Guanethidine**
Profound orthostatic hypotension

**Beta blockers**
Used together on purpose to prevent tachycardia and extra myocardial work

**Diuretics**
Needed to prevent fluid retention and heart failure

## What is monitored

- Blood pressure and heart rate
- Body weight and oedema
- Signs of pericardial effusion: breathlessness, chest pain, muffled heart sounds
- Angina

## Nursing care

- Weigh the patient regularly; report a rapid weight gain or new swelling.
- Check the pulse; report a resting heart rate that rises clearly above the usual value.
- Report shortness of breath, chest pain or dizziness, which can signal pericardial effusion.
- Explain that hair growth on the face and body is an expected effect.

## Pregnancy and breastfeeding

Animal studies showed more fetal resorption in rabbits; it is used in pregnancy only if the benefit clearly justifies the risk.

## Memory aid

MINOXidil: MANY hairs, Oedema, eXtra heartbeats; always with a beta blocker and a diuretic.

## Test yourself

Think of the answer, then tap the question to see it.

## How does minoxidil relax arterioles?

Its sulfate metabolite opens ATP-sensitive potassium channels; the membrane hyperpolarises, calcium entry falls and the muscle relaxes.

## Why is minoxidil given with a beta blocker and a loop or thiazide diuretic?

To counter the reflex tachycardia and the marked salt and water retention caused by the fall in resistance.

## Which serious cardiac effusion can minoxidil cause?

Pericardial effusion, which can progress to cardiac tamponade.

## Which adverse effect led to the topical use of minoxidil?

Hypertrichosis: growth of body hair, used topically to treat androgenetic alopecia.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/minoxidil/)

## Related drugs

- [Hydralazine](https://durgical.com/en/pharmacology/hydralazine/)
- [Propranolol](https://durgical.com/en/pharmacology/propranolol/)

## Related conditions

- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)

[← Back to the class: Direct vasodilators](https://durgical.com/en/pharmacology/classes/direct-vasodilators/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - MINOXIDIL tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0354a7f5-5917-44dc-9963-411104008cb5) (DailyMed (U.S. National Library of Medicine), 2026); [Minoxidil: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682608.html) (MedlinePlus (U.S. National Library of Medicine), 2018); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C02DC01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Farmacología básica y clínica (Katzung), cap. 11 (McGraw Hill, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/minoxidil/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/minoxidil/