Noxidil: Each tablet contains Minoxidil 5 mg.
Noxidil Forte: Each tablet contains Minoxidil 10 mg.
Pharmacology: Pharmacodynamics: Minoxidil is a direct-acting peripheral vasodilator. It does not interfere with vasomotor reflexes; therefore, it does not produce orthostatic hypotension. The drug does not affect CNS function.
Because it causes peripheral vasodilation, minoxidil elicits a reduction of peripheral arteriolar resistance. This action, with the associated fall in blood pressure, triggers sympathetic, vagal inhibitory, and renal homeostatic mechanisms, including an increase in renin secretion, which leads to increased cardiac rate and output, and salt and water retention. These adverse effects can usually be minimized by coadministration of a diuretic and a beta-adrenergic-blocking agent or other sympathetic nervous system suppressant.
Antihypertensive effects: Minoxidil reduces elevated systolic and diastolic blood pressure by decreasing peripheral vascular resistance. The blood pressure response to minoxidil is dose-related and proportional to the extent of hypertension. In humans, forearm and renal vascular resistance decline; forearm blood flow increases while renal blood flow and glomerular filtration rate (GFR) are preserved.
Pharmacokinetics: Absorption/Distribution: Minoxidil is not protein bound and is at least 90% absorbed from the GI tract. Plasma levels of the parent drug reach a maximum within the first hour and decline rapidly thereafter.
Metabolism/Elimination: Predominantly by conjugation with glucuronic acid, 90% is metabolized. Metabolites exert much less pharmacologic effect than minoxidil itself; all are excreted principally in the urine. Renal clearance corresponds to the GFR. Minoxidil and its metabolites are hemodialyzable. Average plasma half-life is 4.2 hours.
Treatment of severe hypertension.
Adults and children over 12 years: Initially 5 mg as a single dose. The dose may be increased gradually to 10, 20, 40 mg daily in single or divided doses if necessary. The maximum recommended dose is 100 mg per day.
Children under 12 years: Initially 0.2 mg/kg body weight as single dose, and may be increased if necessary. The maximum recommended dose is 50 mg per day.
Intervals between dosage adjustments should be at least 3 days or use as directed by the physician.
Special patient populations: Renal impairment: There are no specific dosage recommendations provided; however, patients with renal failure and/or receiving dialysis may require a dosage reduction.
Hepatic impairment: There are no dosage adjustments. Use in patients with severe hepatic impairment is contraindicated.
Mode of Administration: Minoxidil is administered orally.
Symptoms: Limited information is available on the acute toxicity of minoxidil. Severe hypotension after ingestion of minoxidil is most likely to occur in patients with residual sympathetic nervous system blockade from previous therapy with guanethidine or α-adrenergic blockers.
Treatment: In these patients, IV administration of 0.9% sodium chloride injection helps maintain blood pressure and facilitates urine formation. Norepinephrine and epinephrine should be avoided, and vasopressors such as phenylephrine, vasopressin, and dopamine should be used only if a vital organ is underperfused.
Hypersensitivity to any component of the product.
Pheochromocytoma (because the drug may stimulate secretion of catecholamines from the tumor through its antihypertensive action).
Sodium and water retention: Frequently occurred in patients receiving minoxidil and may result in edema, weight gain, congestive heart failure, pulmonary edema, and "refractoriness" to the antihypertensive effects of the drug. Concomitant administration of a diuretic is required except in some patients who are undergoing hemodialysis. Diuretic therapy, alone or with salt restriction, usually minimizes fluid retention, although reversible edema did develop in approximately 10% of patients who were treated in this manner and were not undergoing dialysis. Ascites also has been reported. Rarely, refractory fluid retention may occur, requiring discontinuance of minoxidil; in some patients who can be closely supervised, refractory fluid retention may be treated by discontinuing minoxidil for 1-2 days and then resuming minoxidil therapy in conjunction with vigorous diuretic therapy. In patients on hemodialysis, fluid retention can be controlled with more vigorous ultrafiltration.
ECG changes: ECG changes in the magnitude and direction of the T waves (i.e., positive T waves flatten or invert and negative T waves show increased negativity) occur commonly. Rarely, large negative amplitude of the T wave may encroach upon the ST segment, but the ST segment alone is not changed. ECG changes usually revert to the pretreatment state with continued therapy or when minoxidil is discontinued. No symptoms, evidence of myocardial damage, or deterioration of cardiac function have been associated with minoxidil-induced ECG changes.
Tachycardia/Angina: Minoxidil increase heart rate; this can be minimized by concomitant administration of a β-adrenergic blocking agent or other sympathetic nervous system suppressant. Angina pectoris may worsen or occur in patients without previous angina, probably due to increased oxygen demand associated with increased heart rate and cardiac output and can usually be prevented by a β-blocker or other sympathetic nervous system suppressant.
Pericardial effusion: Occasionally with tamponade, it has occurred in about 3% of patients receiving minoxidil who were not on dialysis, especially in those with inadequate or compromised renal function.
Although pericardial effusion has occurred most often in patients with a connective tissue disease, uremic syndrome, congestive heart failure, or marked fluid retention, there have been instances in which these potential causes of effusion were not present. Patients receiving minoxidil should be observed for signs and symptoms of pericarditis, pericardial effusion, and tamponade, and echocardiograms should be performed if necessary. More vigorous diuretic therapy, dialysis, pericardiocentesis, or surgery may be required and, if effusion persists, withdrawal of minoxidil should be considered. Pericardial effusion is thought to result from minoxidil-induced sodium and water retention. Pericarditis also has been reported in minoxidil-treated patients; however, the relationship of this effect to renal function is unclear.
Hypertrichosis: Within 3-6 weeks after initiating minoxidil therapy, hypertrichosis (elongation, thickening, and increased pigmentation of fine body hair) commonly occurs but is not associated with an endocrine abnormality. Occasionally hypertrichosis may be associated with apparent coarsening of facial features, which may be due to mild generalized fluid retention; transient pruritus may also be associated with hair growth.
Hemodilution: Hematocrit, hemoglobin concentration, and erythrocyte count usually decrease about 7% and then return to pretreatment levels.
Pregnancy: Category C. Minoxidil reduced conception rate and increased fetal absorption in small animals when administered at 5 times the human dose. There are no adequate and controlled studies to date using minoxidil in pregnant women, and the drug should be used during pregnancy only when the potential benefits justify the possible risks to the fetus.
Labor and delivery: The effects of the drug on labor and delivery are not known.
Lactation: Minoxidil is distributed into milk; the drug should not be administered in nursing women.
Pericardial effusion and occasionally with tamponade (3%). Changes in direction and magnitude of T waves occur (approximately 60%).
Initially, hematocrit, hemoglobin, and erythrocyte count usually fall about 7% and then recover to pretreatment levels. Thrombocytopenia and leukopenia (WBC fewer than 3,000/mm3
) have been reported rarely.
Rashes including bullous eruptions (rare) and Stevens-Johnson syndrome.
Lab test abnormalities:
Alkaline phosphatase increased varyingly without other evidence of liver or bone abnormality. Serum creatinine increased an average of 6% and BUN slightly more but later declined to pretreatment levels.
Temporary edema (7%); breast tenderness (fewer than 1%).
Elongation, thickening, and enhanced pigmentation of fine body hair develops within 3 to 6 weeks of starting therapy in approximately 80% of patients.
Diuretics and Hypotensive Agents: When minoxidil is administered with diuretics or other hypotensive drugs, the hypotensive effect of minoxidil is increased. The effect is usually used to therapeutic advantage, but careful adjustment of dosage is necessary when these drugs are used concomitantly. Minoxidil should be administered with caution to patients receiving guanethidine, since concurrent use may cause profound orthostatic hypotensive effects. If possible, guanethidine should be withdrawn several days (1-3 weeks) before minoxidil therapy is begun. If minoxidil must be started in patients receiving guanethidine, the patient should be hospitalized until severe orthostatic effects subside or the patient has learned to avoid activities that cause postural hypotension.
Keep in tight containers below 30°C.
C02DC01 - minoxidil ; Belongs to the class of pyrimidine derivative agents acting on arteriolar smooth muscle. Used in the treatment of hypertension.
Noxidil: Tab 5 mg (white, round, biconvex with a breakline on one side and the figure "5" on the other) x 10 x 10's, 100's.
Noxidil Forte: Tab 10 mg (white, round, biconvex with a breakline on one side and the figure "10" on the other) x 10 x 10's, 100's.