Finasteride vs Topical Minoxidil: Switching Between Them

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How do finasteride and topical minoxidil differ?

Finasteride is a competitive, specific inhibitor of type II 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) [1]. Type II is found in hair follicles, among other tissues, and it drives about two-thirds of circulating DHT; a 1 mg tablet suppresses serum DHT by 65% within 24 hours, and finasteride has no affinity for the androgen receptor [1].

Topical minoxidil is a potassium channel opener and a vasodilator, and how it promotes hair growth is not fully understood [4].

The dosing differs in kind. Finasteride is one 1 mg tablet once daily, with or without food, and daily use for three months or more is usually needed before benefit is seen [1]. Men's 5% minoxidil solution is 1 mL applied with the dropper twice a day to the scalp in the hair loss area; using more or more often does not improve results [2]. Women's 5% minoxidil foam is half a capful once daily [3].

Which one works better in men?

Two randomized trials compared the drugs directly. Arca and colleagues randomized 65 men with androgenetic alopecia to finasteride 1 mg daily (40 men) or 5% topical minoxidil twice daily (25 men) for 12 months; increased hair intensity was seen in 80% (32 of 40) on finasteride and 52% (13 of 25) on minoxidil, and finasteride was judged more effective (P<0.05) [5]. The trial was open-label and small.

In a 450-man Chinese trial, patients took finasteride 1 mg (160 men), 5% topical minoxidil (130) or both (160); at 12 months, 80.5%, 59% and 94.1% respectively had improved, among 428 men evaluated [6].

Against placebo, the finasteride hair-loss program enrolled 1553 men aged 18 to 41 in two 1-year trials and compared 1 mg daily with placebo; hair count in a 1-inch (5.1 cm2) circle of vertex scalp was 107 hairs higher than placebo at 1 year and 138 higher at 2 years [7]. For minoxidil, a 48-week trial of 393 men found 5% solution superior to both 2% solution and placebo for nonvellus hair count, with more itching and local irritation on the 5% strength [8].

An evidence review using American College of Physicians grading concluded that oral finasteride (men only) and topical minoxidil (men and women) are the best-supported treatments for androgenetic alopecia [9].

Can you switch from finasteride to topical minoxidil?

No trial of a direct switch in either direction appears in the evidence for this comparison. What exists is the stopping timeline for each drug. For finasteride, the label says withdrawal leads to reversal of effect within 12 months, and in the vertex trials men switched from finasteride to placebo at 12 months lost the hair-count increase by 24 months [1]. On the minoxidil side, results may occur at 2 months, some men need at least 4 months, and the label says continued use is necessary or hair loss begins again [2]. Measurable changes from minoxidil disappear within months of discontinuation [4].

The men's 5% topical minoxidil solution is labeled for the top of the scalp only and is not intended for frontal baldness or a receding hairline [2]. For finasteride, the Propecia label says efficacy in bitemporal recession has not been established [1].

Can you switch from topical minoxidil to finasteride?

Finasteride's timeline is one 1 mg tablet daily, with three months or more of daily use usually needed before benefit is seen, and continued use to sustain benefit [1]. Propecia is prescription-only and labeled for men only [1].

One point belongs to minoxidil itself: increased hair loss can occur during minoxidil use because of synchronization of the hair cycle, and the shed hairs are usually replaced by thicker hairs in a new growth phase [4].

What happens when finasteride is stopped?

The Propecia label states that withdrawal of treatment leads to reversal of effect within 12 months [1]. In the vertex trials, patients who changed from finasteride to placebo at 12 months had reversal of the hair-count increase 12 months later [1].

Can finasteride and topical minoxidil be used together?

A 450-man randomized trial tested the pair: 94.1% of men on both improved at 12 months versus 80.5% on finasteride and 59% on minoxidil [6]. The finasteride label states that no drug interactions of clinical importance have been identified and that finasteride does not appear to affect the cytochrome P450 system [1].

How do the side effects compare?

In three 12-month controlled trials of finasteride 1 mg (945 men on drug, 934 on placebo), drug-related decreased libido was 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7% and ejaculation disorder 1.2% vs 0.7%; 3.8% vs 2.1% reported one or more of these (p=0.04), and 1.2% vs 0.9% stopped for sexual events [1]. The incidence of each fell to 0.3% or lower by year five [1].

The label's postmarketing section lists sexual dysfunction that continued after discontinuation, including erectile dysfunction, libido disorders, ejaculation disorders and orgasm disorders, and it lists depression, suicidal ideation and behavior; the label states that these voluntary reports come from a population of uncertain size and that a causal relationship cannot reliably be established [1][10]. Propecia carries no boxed warning [1]. Pregnancy is a contraindication in the Propecia label, and the label says women who are or may be pregnant should not handle crushed or broken tablets because of risk to a male fetus [1].

The men's 5% minoxidil Drug Facts warnings cover scalp irritation or redness, unwanted facial hair growth, chest pain, rapid heartbeat, faintness or dizziness, sudden unexplained weight gain, and swelling of the hands or feet [2]. In a 48-week trial of 381 women with female pattern hair loss, the 5% solution produced more itching, irritation and hypertrichosis than 2% solution or placebo [11].

Which product is labeled for which patient?

Finasteride 1 mg is indicated for male pattern hair loss in men only and is not indicated for women [1]. The men's 5% minoxidil solution is for men only and for the vertex [2]. The women's 5% foam is half a capful once daily, with results at about 3 months and up to 6 months for some women [3]. The 2% minoxidil solution has been sold over the counter since its Rx-to-OTC switch was approved on February 9, 1996 [12].