Minoxidil

Hypertension (Oral)

• Initial Dose: Your healthcare provider may start with 5 mg taken once daily.
• Maintenance Dose: The typical range is 10 mg to 40 mg per day, either as a single dose or divided into two doses. The maximum recommended dose is 100 mg per day.

Androgenetic Alopecia (Topical)

• 2% or 5% Solution/Foam: Apply 1 mL or half a capful to the affected areas of the scalp twice daily (morning and night).

• Hypertension: For children under 12 years, the initial dose is typically 0.2 mg/kg per day as a single or divided dose. The dose may be increased in increments of 0.1 to 0.2 mg/kg/day.
• Hair Loss: Minoxidil is generally not approved for the treatment of hair loss in individuals under the age of 18.

Renal Impairment

Patients with renal failure or those undergoing dialysis may require smaller doses. Close medical supervision is necessary to prevent fluid overload.

Hepatic Impairment

Since minoxidil is extensively metabolized by the liver, patients with significant hepatic dysfunction may experience increased systemic levels; dose adjustments may be warranted by your doctor.

Elderly Patients

Clinical studies have not identified significant differences in response between elderly and younger patients, but starting at the lower end of the dosing range is often recommended due to the higher frequency of decreased organ function.

• Oral: May be taken with or without food. It is essential to take it at the same time each day to maintain consistent blood levels.
• Topical: Ensure the scalp and hair are completely dry before application. Wash hands thoroughly after applying. Do not use a hairdryer to dry the scalp after application, as this may reduce efficacy.
• Storage: Store at room temperature (20°C to 25°C / 68°F to 77°F) away from moisture and heat.

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and resume your regular schedule. Do not double the dose to catch up.

Signs of oral overdose include extreme hypotension (low blood pressure), tachycardia (rapid heartbeat), and fluid retention. If an overdose is suspected, contact a poison control center or seek emergency medical attention immediately.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance.

• Hypertrichosis (Oral): Excessive growth of body hair, often appearing on the face, arms, and back. This typically occurs within 3 to 6 weeks of starting oral therapy.
• ECG Changes (Oral): Changes in the T-wave of an electrocardiogram are common but usually asymptomatic.
• Scalp Irritation (Topical): Itching, redness, or flaking at the site of application.

• Tachycardia: An abnormally rapid heart rate as the body compensates for vasodilation.
• Fluid Retention: Swelling of the feet, lower legs, or hands (edema) due to salt and water retention.
• Temporary Hair Shedding: Some users notice increased hair shedding during the first 2-6 weeks of topical use as follicles transition cycles.

• Breast Tenderness: Occasionally reported in both men and women.
• Hypersensitivity: Skin rashes or systemic allergic reactions.
• Leukopenia: A reduction in white blood cell count (extremely rare).

> Warning: Stop taking Minoxidil and call your doctor immediately if you experience any of these.

• Pericardial Effusion: Fluid buildup around the heart, which can lead to cardiac tamponade (a life-threatening compression of the heart).
• Congestive Heart Failure: Indicated by sudden weight gain (more than 5 pounds), shortness of breath, or difficulty breathing while lying down.
• Angina Pectoris: New or worsening chest pain.
• Severe Hypotension: Dizziness, fainting, or extreme lightheadedness.

Prolonged use of oral minoxidil may lead to chronic fluid volume overload if not managed with diuretics. Long-term topical use is generally well-tolerated, though chronic scalp dermatitis may develop in sensitive individuals.

Oral Minoxidil carries an FDA Black Box Warning:

1. 1Cardiovascular Events: Minoxidil can cause pericardial effusion, occasionally progressing to tamponade, and can exacerbate angina pectoris.
2. 2Concomitant Therapy: It must be used under close supervision, usually in combination with a therapeutic dose of a loop diuretic to prevent serious fluid retention and a beta-adrenergic blocking agent to prevent reflex tachycardia.

Report any unusual symptoms to your healthcare provider.

Minoxidil is a high-potency medication. The oral form is strictly reserved for patients who have not responded to other antihypertensive treatments. It should never be used as a first-line therapy for high blood pressure.

No FDA black box warnings exist for topical minoxidil. However, the oral formulation contains a boxed warning stating that it can cause pericardial effusion and may worsen angina. It must be administered with a diuretic and a beta-blocker to manage fluid retention and rapid heart rate.

• Allergic Reactions: Patients with a history of hypersensitivity to minoxidil or any component of the formulation (such as propylene glycol in the liquid topical form) should avoid use.
• Cardiotoxicity: Minoxidil has been associated with heart lesions in animal studies; while not clearly established in humans, cardiac function must be monitored.
• Fluid/Electrolyte Balance: Oral use leads to significant sodium and water retention. Patients must be monitored for weight gain and edema.
• Tachycardia: The drug causes reflex stimulation of the heart. Patients with unstable angina or recent myocardial infarction (heart attack) are at high risk.

• Weight: Patients taking oral minoxidil should weigh themselves daily to detect fluid retention.
• Heart Rate/BP: Regular monitoring of resting heart rate and blood pressure is mandatory.
• Renal Function: Periodic blood urea nitrogen (BUN) and creatinine tests.
• Chest X-ray/Echocardiogram: If signs of pericardial effusion appear, imaging is required.

Minoxidil may cause dizziness or fainting due to low blood pressure. Patients should exercise caution when driving or operating heavy machinery until they know how the medication affects them.

Alcohol can further dilate blood vessels and may enhance the blood-pressure-lowering effects of minoxidil, increasing the risk of dizziness and syncope (fainting).

Do not stop taking oral minoxidil abruptly, as this can lead to rebound hypertension. For topical use, stopping treatment will result in the loss of regrown hair within 3 to 4 months.

> Important: Discuss all your medical conditions with your healthcare provider before starting Minoxidil.

• Guanethidine: Concurrent use with oral minoxidil can cause profound orthostatic hypotension (a sudden drop in blood pressure when standing). Guanethidine should be discontinued at least one week before starting minoxidil.

• Other Antihypertensives: Drugs like ACE inhibitors, beta-blockers, and calcium channel blockers may have additive effects, leading to excessively low blood pressure.
• Diuretics: While often prescribed together, the combination requires careful monitoring of electrolyte levels and fluid status.

• NSAIDs (e.g., Ibuprofen, Naproxen): These medications can cause sodium retention and may decrease the antihypertensive efficacy of minoxidil.
• Erectile Dysfunction Medications (e.g., Sildenafil): These also lower blood pressure and may cause symptomatic hypotension when used with minoxidil.

• Sodium Intake: High salt intake can counteract the effects of minoxidil and worsen fluid retention. A low-sodium diet is often recommended by healthcare providers.
• Caffeine: May increase heart rate, potentially complicating the reflex tachycardia caused by minoxidil.

• Hawthorn: May have mild blood-pressure-lowering effects and could theoretically enhance minoxidil's action.
• Licorice Root: Known to cause sodium retention and potassium loss, which may interfere with hypertension management.

Minoxidil does not have well-documented interactions with common laboratory tests, though it may cause non-specific changes in ECG readings (T-wave changes).

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking.

• Pheochromocytoma: Minoxidil may stimulate the secretion of catecholamines from the tumor, leading to a dangerous spike in blood pressure.
• Hypersensitivity: Known allergy to minoxidil or any inactive ingredients in the formulation.

• Recent Myocardial Infarction: The reflex tachycardia and increased cardiac output may worsen heart damage.
• Pericardial Effusion: Existing fluid around the heart may be exacerbated by the drug's tendency to cause fluid retention.
• Renal Failure (Not on Dialysis): Requires extreme caution due to the risk of severe fluid overload.

While no specific cross-sensitivities are widely documented, patients sensitive to other vasodilators should be monitored closely. Some topical formulations contain propylene glycol, which is a common skin allergen; in such cases, the foam version (which is propylene glycol-free) may be an alternative.

> Important: Your healthcare provider will evaluate your complete medical history before prescribing Minoxidil.

FDA Pregnancy Category C. There are no adequate and well-controlled studies in pregnant women. Animal studies have shown some evidence of fetal risk. Oral minoxidil should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Topical minoxidil is generally not recommended for use during pregnancy.

Minoxidil has been reported to pass into human breast milk. Because of the potential for serious adverse reactions in nursing infants from systemic absorption, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.

Safety and effectiveness in pediatric patients have not been established for hair loss. For hypertension, use in children is limited, and dosing must be strictly weight-based (mg/kg) under the guidance of a pediatric specialist.

Elderly patients are at a higher risk for cardiovascular side effects and renal impairment. They should be monitored closely for signs of heart failure and orthostatic hypotension. Dose selection should be cautious, usually starting at the low end of the range.

Patients with impaired renal function may require lower doses of oral minoxidil. Since the drug is primarily excreted by the kidneys, accumulation can occur, increasing the risk of side effects.

Pharmacokinetic data in patients with hepatic impairment are limited. However, as the liver is the primary site of metabolism, your doctor may monitor liver function and adjust the dose accordingly.

> Important: Special populations require individualized medical assessment.

Minoxidil is an Arteriolar Vasodilator. It acts by opening ATP-sensitive potassium channels in the smooth muscle cells of the peripheral arterioles. This action leads to potassium efflux, membrane hyperpolarization, and subsequent relaxation of the vascular smooth muscle. It does not affect the venous system. In the scalp, it is converted by the enzyme sulfotransferase into its active form, minoxidil sulfate, which is thought to stimulate hair follicles.

• Onset of Action: For hypertension, the effect begins within 30 minutes. For hair growth, visible results usually require 2 to 4 months of consistent topical use.
• Duration: The antihypertensive effect lasts approximately 24 to 75 hours after a single oral dose.
• Tolerance: Tolerance does not typically develop to the vasodilatory effects, though fluid retention can mask the blood-pressure-lowering benefits.

| Parameter | Value |

|---|---|

| Bioavailability | ~90% (Oral); <2% (Topical) |

| Protein Binding | 0% |

| Half-life | 3-4.2 hours (Plasma) |

| Tmax | 1 hour (Oral) |

| Metabolism | Hepatic (90%) via Glucuronidation |

| Excretion | Renal 97% |

• Molecular Formula: C9H15N5O
• Molecular Weight: 209.25 g/mol
• Solubility: Slightly soluble in water; soluble in propylene glycol and ethanol.
• Structure: A pyrimidine derivative (2,4-diamino-6-piperidinopyrimidine 3-oxide).

Minoxidil is a peripheral vasodilator. It is distinct from other antihypertensives like ACE inhibitors or beta-blockers as it acts directly on the vessel walls. Related medications include Hydralazine.