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minoxidil (Loniten, Rogaine)
Tradename: Loniten.
Indications:
1) management of severe hypertension
a) symptomatic hypertension
b) associated end-organ damage
2) used with loop diuretic to prevent fluid retention
3) prevention & reversal of male pattern baldness
Contraindications: pheochromocytoma
Caution:
1) coronary artery disease
2) recent myocardial infarction
3) pulmonary hypertension
4) renal insufficiency
5) congestive heart failure
Dosage:
1) start 5 mg PO QD
2) increase every 3 days
3) average effective dose: 10-40 mg/day
4) max: 100 mg/day
5) androgenetic alopecia: 2.5 mg/day
Tabs: 2.5 mg, 10 mg.
Topical agent: Tradename Rogaine.
1 mL to dry scalp BID.
Packaging: solution 2%.
Pharmacokinetics:
1) oral bioavailability is 90%
2) onset of hypotensive effect (oral): 30 minutes
3) peak hypotensive effect (oral): within 2-8 hours
4) duration of action: up to 2-5 days
5) an average of 7 days for maximum effect
6) plasma protein binding is negligible
7) metabolized by liver to glucuronide derivative
8) excreted in the urine
Adverse effects:
1) common (> 10%)
- hypertrichosis*, transient EKG T-wave changes, reflex tachycardia, palpitations, congestive heart failure, edema 2 less common (1-10%)
- fluid & electrolyte imbalance (Na+ retention & H2O retention resulting in edema)
3) uncommon (< 1%)
- rash, thrombocytopenia, leukopenia, breast tenderness, angina, pericardial effusion#, pericardial tamponade, dizziness, headache, coarsening of facial features, Stevens-Johnson syndrome, sunburn, weight gain
* hypertrichosis commonly occurs within 1-2 months of therapy
# increased risk of pericardial effusion with renal insufficiency
Drug interactions:
- guanethidine in combination may result in profound orthostatic hypotension; discontinue guanethidine 1-3 weeks prior to starting minoxidil or initiate therapy in hospital
Mechanism of action:
1) potent vasodilator
2) reduces peripheral vascular resistance (decreases afterload)
- reflex tachycardia may occur
3) lowers blood pressure
4) greater effect on arterioles than veins
Interactions
drug interactions
drug adverse effects of antihypertensive agents
General
vasodilator agent
Properties
MISC-INFO: elimination route KIDNEY
pregnancy-category C
safety in lactation -
Database Correlations
PUBCHEM cid=4201
References
- The Pharmacological Basis of Therapeutics, 9th ed.
Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- Drug Information & Medication Formulary, Veterans Affairs,
Central California Health Care System, 1st ed., Ravnan et al
eds, 1998
- Kaiser Permanente Northern California Regional Drug
Formulary, 1998
Component-of
biotin/minoxidil