Minoxidil: Uses and Side Effects

What Is Minoxidil?

Mechanism of Action

• Opens ATP-sensitive K+ (K-ATP) channels in vascular smooth muscle
• Causes K+ efflux, hyperpolarization, and relaxation of smooth muscle
• Results in selective arteriolar dilation (no effect on venous/capacitance vessels)

• Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 657
• Katzung's Basic and Clinical Pharmacology, 16th Ed., p. 281

Therapeutic Uses

1. Severe/Refractory Hypertension (Oral)

• A diuretic (to counteract fluid retention; often a loop diuretic is needed)
• A beta-blocker (to control reflex sympathetic activation)
• Sometimes an ACE inhibitor or ARB (to prevent cardiac remodeling)

2. Androgenetic Alopecia (Topical)

• 2% solution - approved for women; also used in men
• 5% solution - recommended for men due to greater efficacy (also available as 5% foam)
• Vertex balding responds better than frontal baldness
• Effects are not permanent - hair loss resumes within 4-6 months of stopping treatment

3. Other Alopecia Types (Off-label, Low-Dose Oral)

• Telogen effluvium
• Frontal fibrosing alopecia
• Lichen planopilaris
• Chemotherapy-induced alopecia
• Katzung's, p. 281; Goodman & Gilman's, p. 658

Side Effects

1. Fluid and Salt Retention

• Increased proximal renal tubular sodium reabsorption (secondary to reduced renal perfusion and reflex alpha-adrenergic stimulation)
• Peripheral edema
• May require escalation to loop diuretics (thiazides often insufficient), especially with renal impairment

2. Cardiovascular Effects (Reflex Sympathetic Activation)

• Tachycardia and palpitations (reflex baroreceptor response to vasodilation)
• Increased myocardial oxygen consumption - can precipitate angina in patients with coronary artery disease
• Increased cardiac output (3-4x in some cases)
• Left ventricular filling pressure rise - in patients with LVH and diastolic dysfunction, this can cause cardiac failure
• Pulmonary hypertension (secondary to fluid overload)
• Pericardial effusion - uncommon but serious; can progress to tamponade if untreated
• ECG changes: Flattened/inverted T-waves (not ischemic; related to K+ channel activation)
• Renin and aldosterone secretion are increased (attenuated by beta-blockers or ACE inhibitors)

3. Hypertrichosis

• Excessive hair growth, particularly on the face, arms, and back
• Most bothersome in women
• Occurs with systemic (oral) use
• With low-dose oral use, this is a common and expected cosmetic side effect
• Topical use for scalp hair loss paradoxically causes hypertrichosis at distant sites in a minority of patients

4. Topical-Specific Side Effects

• Scalp irritation and contact/irritant dermatitis (partly due to propylene glycol in solution formulations; foam is better tolerated)
• Initial hair shedding in the first weeks - this is normal and indicates the drug is working (new anagen hairs pushing out telogen hairs); treatment should not be stopped
• Systemic absorption is minimal through normal scalp, but increases with broken or inflamed skin - caution in cardiac patients

5. Other

• Headache
• Sweating
• Orthostatic hypotension (in topical use, mild; more relevant with oral dosing)
• Goodman & Gilman's, pp. 657-659; Katzung's, pp. 281

Important Clinical Notes

Management of Cold + Fever + Cough (Upper Respiratory Tract Infection)

First: Establish the Likely Cause

• Cummings Otolaryngology, p. 1139

Key Principle: This is Viral - Antibiotics Are NOT Indicated

Step-by-Step Management

1. Non-Pharmacological (First Line)

• Rest - essential for recovery
• Oral hydration - fluids help loosen secretions and prevent dehydration from fever
• Warm fluids (soups, herbal teas) - soothing for throat and airways
• Saline nasal rinses - reduces nasal congestion and clears secretions
• Steam inhalation - temporary relief of nasal blockage
• Humidifier - helps with dry air, especially at night

2. Pharmacological - Symptomatic Treatment

A. For Fever and Body Aches

B. For Nasal Congestion / Runny Nose

C. For Cough

D. For Sore Throat

• Lozenges (benzocaine, menthol)
• Warm salt water gargles
• Ibuprofen/paracetamol (systemic)
• Benzydamine spray (topical anti-inflammatory)

3. Special Consideration: Is It Influenza?

• Oseltamivir (Tamiflu) 75 mg twice daily x 5 days - effective if started within 48 hours of symptom onset
• Indicated especially in high-risk patients (elderly, immunocompromised, pregnant, chronic lung/heart disease)

4. Pediatric Considerations

• No OTC cough/cold medicines for children under 4 years (risk of serious adverse effects, no proven benefit)
• Use paracetamol or ibuprofen for fever in children
• Honey for cough in children >1 year (never in infants under 1 year - botulism risk)
• Saline nasal drops are safe and effective for nasal congestion in infants
• Aspirin is contraindicated in children

Red Flags - When to Escalate / Add Antibiotics

Summary Prescription Template (Adult, Uncomplicated Viral URTI)

1. Tab. Paracetamol 500 mg - 1-2 tabs every 6 hrs as needed for fever/pain (max 4g/day)
2. Tab. Cetirizine 10 mg - once at night (for runny nose/sneezing)
3. Pseudoephedrine 60 mg - every 6-8 hrs if significant nasal congestion (avoid in hypertensives)
4. Dextromethorphan 15 mg - every 6-8 hrs for dry cough (or guaifenesin 400 mg for wet cough)
5. Warm fluids, rest, adequate hydration
6. Return if: fever persists beyond 5-7 days, difficulty breathing, ear pain, or worsening symptoms

Important reminder: This is a clinical overview. Always tailor treatment to the individual patient's age, comorbidities, other medications, and local antibiotic guidelines. - Cummings Otolaryngology; CDC Common Cold Guidelines 2024; AAFP Treatment of Common Cold

Patient with Cough + Cold + Fever - What to Suggest

Quick Assessment First

• How long? (>7-10 days without improvement = red flag)
• How high is the fever? (>38.5°C sudden onset = suspect influenza)
• Productive or dry cough? (changes the cough medicine choice)
• Age? (children <4 years - no OTC cold medicines)
• Any comorbidities? (HTN, heart disease, pregnancy - affects drug choice)

This is Almost Always Viral - NO Antibiotics Routinely

Treatment Plan

Non-Drug Measures (Always Recommend)

• Rest
• Plenty of warm fluids (water, soups, herbal teas)
• Saline nasal rinse / steam inhalation
• Salt water gargling for sore throat

Drug Treatment by Symptom

If Influenza is Suspected (High fever, sudden onset, severe body ache)

• Oseltamivir (Tamiflu) 75 mg twice daily x 5 days
• Must start within 48 hours of symptom onset for best effect

Sample Prescription (Uncomplicated Adult Cold)

1. Tab. Paracetamol 500 mg - 1 tab every 6 hrs for fever/pain
2. Tab. Cetirizine 10 mg - 1 tab at night for cold/runny nose
3. Dextromethorphan 15 mg - every 8 hrs for dry cough (or Guaifenesin for wet cough)
4. Xylometazoline nasal spray - 2 sprays each nostril twice daily (max 5 days)
5. Warm fluids + rest

Red Flags - Refer or Escalate

Note: Always adjust for patient age, allergies, and other medications. Children under 4 should NOT receive OTC cough/cold medicines. Aspirin is contraindicated in children under 16.