Oral Minoxidil: What to Expect Week by Week During Your First Month

Why visible scalp change is slow to appear

Body hair and scalp hair follow different timelines. The tablet label describes hypertrichosis, the elongation, thickening and darkening of fine hair, starting within 3 to 6 weeks, first at the temples, between the eyebrows and in the sideburns, then spreading to the back, arms, legs and scalp [2].

Scalp hair gains are measured in months. In an open-label study of 30 men with androgenetic alopecia on 5 mg daily, total hair counts rose by a mean of 26 hairs/cm2 at week 12 and 35.1 hairs/cm2 at week 24, both statistically significant [1]. Even topical minoxidil, applied straight to the scalp, is labeled to produce results at 2 months with twice-daily use, and some men need at least 4 months [6].

Week 1: the drug is in the bloodstream

Oral minoxidil is at least 90% absorbed, plasma levels peak within the first hour, and the average plasma half-life is 4.2 hours [2]. Blood pressure begins to fall within 30 minutes of a dose, reaches its lowest at 2 to 3 hours, and the effect lasts about 75 hours [2]. The label does not describe how minoxidil grows hair; it describes a direct-acting peripheral arteriolar vasodilator that lowers blood pressure by decreasing peripheral vascular resistance [2].

The side-effect figures below come from patients treated for months, not weeks: in 1404 patients treated for at least 3 months, lightheadedness was reported by 1.7%, fluid retention by 1.3%, tachycardia by 0.9%, headache by 0.4% and periorbital edema by 0.3% [3].

Week 2: shedding during minoxidil treatment

A review of minoxidil in dermatology describes increased hair loss during treatment as a result of the hair-cycle synchronization the drug induces: resting follicles shed and are usually replaced by thicker hairs in a new growth phase [7]. That description is of minoxidil in general. The oral minoxidil study measured hair counts at weeks 12 and 24, so it does not show when shedding begins in the first month [1].

The extra body hair is not hormonal. The tablet label describes hypertrichosis without virilism, with no endocrine abnormality found to explain it [2].

Week 3: body and facial hair can start

At the doses the tablet is approved for, hypertrichosis occurs in about 80% of patients and develops within 3 to 6 weeks [2]. At the low doses used for hair, it is still the most frequent adverse effect: 15.1% of 1404 patients, and it led to withdrawal in 14 of them (0.5%) [3]. In a meta-regression of six observational studies in androgenetic alopecia, each additional 1 mg/day was associated at 6 months with mean differences of 17.9% in hypertrichosis risk and 4.8% in cardiovascular adverse-event risk. These associations do not establish that the dose caused the outcomes [8].

The label says new hair growth stops when minoxidil is discontinued, but 1 to 6 months may be needed for the appearance to return to pretreatment [2].

Week 4: blood pressure and heart rate data

Blood pressure and heart rate data for low doses come from a meta-analysis of uncontrolled studies of low-dose oral minoxidil at 5 mg/day or less. It found no significant change in systolic pressure (mean difference -0.13 mm Hg, 95% CI -2.67 to 2.41) or diastolic pressure (-1.25, 95% CI -3.21 to 0.71), a significant rise in heart rate (+2.67 beats/min, 95% CI 0.34 to 5.01), and hypotensive symptoms in 119 patients (5.0%) with no hypotensive episodes [4].

What the tablet label says to watch for

The oral label carries a boxed warning, written for antihypertensive doses: pericardial effusion, occasionally progressing to tamponade, and angina that may be exacerbated [2]. The label reserves the drug for hypertension that has not responded to maximum doses of a diuretic plus two other antihypertensives, and says it must be given under close supervision, usually with a beta blocker to prevent tachycardia and a diuretic to prevent serious fluid accumulation [2].

Other label figures: temporary edema in 7% of patients who were not edematous at the start, reversible edema in about 10% of non-dialysis patients despite a diuretic, and pericardial effusion in about 3% of treated patients not on dialysis, especially those with impaired kidney function [2]. Minoxidil tablets are contraindicated in pheochromocytoma and in hypersensitivity to any component [2]. The label states the drug has not been studied in patients within 1 month of a heart attack [2].

Guanethidine is the only drug interaction named in the oral label. The pair can cause profound orthostatic hypotension, and the label says to stop guanethidine before starting minoxidil where possible, or otherwise start minoxidil in hospital [2].

Doses used for hair, and how they compare with the label

The tablet label starts adults at 5 mg once daily and increases to 10, 20 and then 40 mg, with a usual effective range of 10 to 40 mg/day and a maximum of 100 mg/day, adjusting no more often than every 3 days [2]. Hair-loss studies have used 1 mg daily [5] and 5 mg daily [1].

In one double-blind 24-week trial of 90 men, oral minoxidil 5 mg daily and topical minoxidil 5% twice daily did not differ significantly in the reported frontal or vertex hair-density outcomes: the difference in frontal terminal hair density was 3.1 hairs/cm2 (95% CI -18.2 to 21.5; P=.27), and the difference in vertex density was 23.4 hairs/cm2 (95% CI -0.3 to 43.0; P=.09) [9]. A separate trial of 65 patients found both 1 mg oral and 5% topical improved hair diameter over 6 months, with no significant difference between the groups [5].

When the payoff comes

A pilot of a combination capsule of minoxidil 0.25 mg plus spironolactone 25 mg, not minoxidil alone, in 100 women over 12 months found a mean hair-loss severity score reduction of 0.85 at 6 months and 1.3 at 12 months, and a mean shedding score reduction of 2.3 and 2.6 [10]. A review of 17 studies covering 634 patients concluded that oral minoxidil is effective and well tolerated in healthy patients who struggle with topical use, and that larger randomized dose-comparison studies are needed [11].

For month one, the drug reaches peak plasma levels within an hour of a dose [2], the oral study's hair-count gains were reported at weeks 12 and 24 [1], and extra facial or body hair can begin within 3 to 6 weeks at the tablet label's antihypertensive doses [2].