Topical Minoxidil Plateau & Non-Response: A Clinical Troubleshooting Guide

Is It a Plateau, or Is It Maintenance?

The men's 5% solution label says continued use is necessary to increase and keep hair regrowth, or hair loss will begin again [1].

The topical trials measured outcomes at 16 or 48 weeks, so they do not show what happens to hair density after a year [7][8][9].

The label's timelines are modest. Results may occur at 2 months with twice-daily use, and some men need at least 4 months before they see anything [1]. The women's 5% foam label says results may occur at 3 months with once-daily use, and some women need at least 6 months [3].

What the Label Says When Regrowth Does Not Come

The men's 5% solution label lists no hair regrowth after 4 months among its stop-use signs [1]. The women's 5% foam label uses 6 months [3].

The labels also set out limits on who the product is for and how it is applied:

• Amount and frequency. Men's 5% solution: 1 mL twice daily directly onto the scalp in the hair loss area [1]. Women's 5% foam: half a capful once daily [3].
• Site. The men's 5% solution is labeled for the top of the scalp (vertex) only and is not intended for frontal baldness or a receding hairline [1].
• More is not better. The labels state that using more or more often will not improve results [1][3].
• Right product for the person. The 5% solution is labeled for men only [1]. Women's over-the-counter options include the 2% solution [10] and the 5% foam once daily [3].
• Conditions the product is not for. The labels list scalp redness, inflammation, infection, irritation or pain, and use of other scalp medicines; the women's label adds hair loss associated with childbirth [1][3].
• Stop-use signs. The labels list chest pain, rapid heartbeat, faintness or dizziness, sudden unexplained weight gain, swelling of the hands or feet, scalp irritation or redness, and unwanted facial hair growth [1][3]. Heart disease appears on both labels as a warning for people who have it [1][3].

How Common Is True Non-Response?

A sulfotransferase activity test using plucked hair follicles was studied as a predictor of response to topical minoxidil [2]. In one analysis of completed and ongoing studies of that test, it ruled out 95.9% of nonresponders [2]. The same analysis states that clinical response is usually seen at 3 to 6 months and that approximately 40% of patients will regrow hair on 5% topical minoxidil [2].

Foam Compared With Solution

In a 24-week single-blind trial of 113 women with androgenetic alopecia, 5% minoxidil foam used once daily was noninferior to 2% solution used twice daily on change in nonvellus target-area hair count and hair width [4]. The foam group had significantly lower rates of local intolerance (P=.046), especially itching and dandruff, and rated the product better on not interfering with styling (P=.002) [4].

Irritation is a feature of the stronger solution. In the 48-week trial of 393 men, itching and local irritation were more frequent with 5% solution than with 2% solution or placebo [7]. In the 48-week trial of 381 women, itching, irritation and hypertrichosis were more frequent with 5% solution than with 2% or placebo [8], although the over-the-counter 5% solution is labeled for men only [1].

The foam comparisons in the cited trials are foam against placebo in 352 men, where hair counts increased significantly (P<.0001) over 16 weeks [9], and foam once daily against 2% solution twice daily in women [4]. Neither compared 5% foam with 5% solution head to head.

Does a Stronger Topical or Oral Minoxidil Help?

The over-the-counter products are 2% and 5% [10]. For someone using 2%, the step to 5% is documented: in men, 5% solution was significantly superior to 2% solution and placebo for change in nonvellus hair count over 48 weeks, and response occurred earlier with 5% [7]. In women, 5% solution was superior to placebo on all three primary measures at week 48 and superior to 2% solution on patient assessment of treatment benefit [8]. For someone already on 5%, those trials offer no next concentration.

Oral minoxidil is not FDA-approved for hair loss; the tablet label states that use of minoxidil tablets, in any formulation, to promote hair growth is not an approved indication [11]. The 65-patient randomized trial did not test oral minoxidil as a rescue after a topical plateau. It compared 1 mg/day oral minoxidil with 5% topical solution for 6 months, and both improved hair diameter with no significant difference between groups [5].

A review of 17 studies and 634 patients concluded oral minoxidil appeared effective and well tolerated in healthy patients who have difficulty with topical formulations, citing twice-daily application, hair texture and scalp irritation as the problems [12]. In a retrospective study of 1404 patients on low-dose oral minoxidil, with no control group, hypertrichosis occurred in 15.1%, lightheadedness in 1.7%, fluid retention in 1.3% and tachycardia in 0.9%; 1.2% discontinued because of systemic adverse effects, and no life-threatening effects were observed [13]. A meta-analysis of uncontrolled studies of 5 mg/day or less found no significant change in systolic blood pressure (-0.13 mm Hg, 95% CI -2.67 to 2.41), heart rate up 2.67 beats/min (95% CI 0.34 to 5.01), hypotensive symptoms in 5.0% and no hypotensive episodes [14]. The tablet label's boxed warning (pericardial effusion, angina, fluid retention) is written for antihypertensive doses [11].

Adding Finasteride to Topical Minoxidil

A 12-month randomized trial enrolled 450 men with male-pattern hair loss, assigned to finasteride 1 mg/day, 5% topical minoxidil, or both; 428 were evaluated [6]. Improvement was seen in 80.5% on finasteride, 59% on minoxidil alone, and 94.1% on the combination, and adverse reactions were rare (1.8% with finasteride, 6.1% with minoxidil) [6]. The trial compared the three strategies from the start of treatment; it did not test finasteride as a rescue after a plateau [6].