What are the side effects of minoxidil and finasteride?

Side Effects of Minoxidil and Finasteride

Both minoxidil and finasteride have significant side effects that patients should be aware of before starting treatment, with finasteride causing sexual dysfunction in up to 18.5% of men and minoxidil commonly causing scalp irritation and unwanted hair growth.

Minoxidil Side Effects

Topical Minoxidil

• Common side effects:
  • Scalp irritation and itching (most common) 1
  • Skin redness at application site 1
  • Burning sensation, especially if it contacts eyes 1
  • Unwanted hair growth on face or other body parts (rare but reversible) 1

Systemic Minoxidil (Oral)

• Cardiovascular effects:
  • Fluid retention requiring concomitant diuretic use 2, 3
  • Reflex tachycardia (requires beta-blocker to counteract) 2, 3
  • Potential for hypotension 3
• Other effects:
  • Sodium and water retention 3
  • In rare cases, pericardial effusion 3

Finasteride Side Effects

Sexual Side Effects

• Impotence: 8.1% in first year, 5.1% in years 2-4 4
• Decreased libido: 6.4% in first year, 2.6% in years 2-4 4
• Decreased ejaculate volume: 3.7% in first year, 1.5% in years 2-4 4
• Ejaculation disorder: 0.8% in first year, 0.2% in years 2-4 4

Other Side Effects

• Breast-related:
  • Breast enlargement: 0.5% in first year, 1.8% in years 2-4 4
  • Breast tenderness: 0.4% in first year, 0.7% in years 2-4 4
• Dermatological:
  • Rash: 0.5% in first year, 0.5% in years 2-4 4
  • Increased growth of other body hair (reported in some studies) 5

Comparative Efficacy and Safety

• In direct comparison studies, oral finasteride (1mg/day) showed higher efficacy than 5% topical minoxidil for male pattern hair loss, with 80.5% vs 59% improvement rates respectively 6
• Combination therapy with both medications showed the best efficacy (94.1% improvement) 6
• Recent research shows that topical finasteride (0.25%) combined with minoxidil (3%) may provide superior efficacy to minoxidil alone while minimizing systemic side effects of finasteride 7

Important Considerations

For Minoxidil:

• Results may take 2-4 months to appear 1
• Treatment must be continued indefinitely to maintain results 1
• If application is missed for one day, it will not affect overall results 1
• Should not be used by women who are pregnant or breastfeeding 1
• Should not be used on irritated or damaged scalp 1

For Finasteride:

• Sexual side effects may persist even after discontinuation in some patients
• Approximately 3.7% of patients discontinue therapy due to sexual side effects 4
• Should not be handled by pregnant women due to potential risks to male fetus 4
• May decrease PSA levels, which should be considered in prostate cancer screening 4

Alternative Approaches

For patients concerned about side effects, newer approaches include:

• Topical finasteride formulations (0.1-0.25%) that may reduce systemic absorption 8, 7
• Maintenance therapy with topical minoxidil/finasteride combination after initial oral treatment 8

Remember that both medications require continuous use to maintain results, and discontinuation will lead to reversal of any hair growth benefits within months.