BLACK BOX WARNING
- pericarditis/pericardial effusion
- can exacerbate angina; use with beta-blocker
- requires concurrent diuretic therapy
minoxidil
Brand: Loniten (oral), Rogaine (topical)
⚠ BBW Prototype: hydralazine
Drug Class: direct vasodilator / potassium channel activator
Drug Family: antihypertensive
Subclass: arteriolar dilator
Organ Systems: cardiovascular
Mechanism of Action
Opens ATP-sensitive K+ channels in vascular smooth muscle causing hyperpolarization and profound arteriolar vasodilation; minoxidil sulfate is active metabolite.
ATP-sensitive potassium channels (smooth muscle)
Indications
- severe/resistant hypertension (oral)
- alopecia (topical)
Contraindications
- pheochromocytoma
- pulmonary hypertension from mitral stenosis
Adverse Effects
Common
- reflex tachycardia
- fluid retention (require loop diuretic)
- hypertrichosis (>80% of patients)
- pericardial effusion
Serious
- pericardial effusion/tamponade
- pulmonary hypertension
- angina worsening
Pharmacokinetics (ADME)
| Absorption | 90% oral bioavailability |
| Distribution | wide |
| Metabolism | hepatic sulfation to active minoxidil sulfate |
| Excretion | renal |
| Half-life | 4.2 hours |
| Onset | 30 min |
| Peak | 2-3 hours |
| Duration | 2-5 days (prolonged effect despite short half-life) |
| Protein Binding | <3% |
| Vd | large |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| guanethidine | profound orthostatic hypotension | major |
Nursing Considerations
- Must always be used with a loop diuretic AND a beta-blocker (prevents severe fluid retention and reflex tachycardia)
- Monitor for pericardial effusion — echocardiogram if suspected
- Warn about hypertrichosis (fine body hair growth) — common, cosmetically distressing
- Reserved for resistant hypertension unresponsive to three agents
Clinical Pearls
- Reserved for severe resistant hypertension — third/fourth line only
- Three-drug rule: minoxidil requires concurrent beta-blocker + loop diuretic
- Hypertrichosis (mechanism of Rogaine topical)
Safety Profile
Pregnancy avoid
Lactation avoid
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
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