Dosing and uses of Loniten, Minodyl (minoxidil)
Adult dosage forms and strengths
tablet
- 2.5mg
- 10mg
Severe or Refractory Hypertension (HTN)
Initial: 5mg PO qDay, increase every 3 days PRn
Maintenance: 2.5-80 mg/day qDay or q12hr; not to exceed 100 mg/day
Pediatric dosage forms and strengths
tablet
- 2.5mg
- 10mg
Severe or Refractory Hypertension (HTN)
< 12 years
- Initial: 0.1-0.2 mg/kg; not to exceed 5 mg/day PO; titrate to response every 3 days
- 0.25-1 mg/kg/day PO qDay or q12hr; not to exceed 50 mg/day
> 12 years
- Initial: 5mg PO qDay, increase every 3 days PRN
- Maintenance: 2.5-80 mg/day qDay or q12hr; not to exceed 100 mg/day
Geriatric dosage forms and strengths
Hypertension
2.5 mg PO qDay; titrate to response gradually
Loniten, Minodyl (minoxidil) adverse (side) effects
>10%
Hypertrichosis (80%)
Abnormal ECG (60%)
1-10%
Pericardial effusion (3%)
Frequency not defined
Angina
Cardiac tamponade
Fluid and sodium retention
Hypotension
Pericarditis
Tachyarrhythmia
Stevens-Johnson syndrome (rare )
Hirsutism
Leukopenia (rare)
Thrombocytopenia (rare)
Toxic epidermal necrolysis
Warnings
Black box warnings
Can precipitate effusion, occasionally progressing to tamponade
May exacerbate angina pectoris
Reserve for patients who do not respond adequately to maximum therapeutic doses of a diuretic and 2 other antihypertensives
In experimental animals, minoxidil caused several kinds of myocardial lesions as well as other adverse cardiac effects
Must be administered under close supervision, usually concomitantly with therapeutic doses of a beta-adrenergic blocking agent to prevent tachycardia and increased myocardial workload
Usually given with a diuretic (typically loop diuretic) to prevent serious fluid accumulation
Patients with malignant hypertension and those already receiving guanethidine should be hospitalized when minoxidil first administered (monitoring required because risk for rapid/large decrease in BP)
Contraindications
Hypersensitivity to minoxidiL
Pheochromocytoma
Cautions
Use with B-blocker or centrally-acting drug and a diuretic
Reserve for severe hypertension refractory to other drugs
Pericarditis and pericardial effusion with tamponade reported; observe patients closely for any suggestion of cardiac disorder; perform echocardiographic studies if cardiac disorder suspected; may treat with diureticsdialysis, pericardiocentesis or surgery; discontinue therapy if effusion persists
In patients with severe blood pressure elevation, too rapid control of blood pressure, especially with intravenous agents, can precipitate syncope, cerebrovascular accidents, myocardial infarction and ischemia of special sense organs with resulting decrease or loss of vision or hearing; patients with compromised circulation or cryoglobulinemia may also suffer ischemic episodes of affected organs
Patients with malignant hypertension should have initial treatment with minoxidil carried out in a hospital setting, both to assure that blood pressure is falling and to assure that it is not falling more rapidly than intended
Tablets have not been used in patients who have had a myocardial infarction within preceding month; use caution
Neonatal hypertrichosis reported following exposure to minoxidil during pregnancy
May exacerbate heart failure
Pregnancy and lactation
Pregnancy category: C
Lactation: controversial; excreted in breast milk, not recommended for long term use if breastfeeding
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Loniten, Minodyl (minoxidil)
Mechanism of action
Direct vasodilator; dilate arterioles with little effect on vein, decreases systemic resistance, which subsequently decreases blood pressure.
Pharmacokinetics
Half-Life: 4 hr
Excretion: Urine (12% as unchanged drug)
Duration: 2-5 Days
Peak Plasma Time: PO (HTN): 1 hr
Bioavailability: PO (HTN): 90%
Protein Bound: Negligible
Metabolism: liver, 88% via glucuronidation
Metabolite: minoxidil-0-glucuronide (active)
Onset
- Initial effect: PO (HTN): 30-60 min
- Max effect: PO (HTN): 4-8 hr
