Can I Take Glycine with Topical Minoxidil?

Is There Any Known Interaction?

No interaction between glycine and topical minoxidil is known. No human interaction studies of glycine with other common drugs were found in the trials cited on this page [1]. The only interaction signal in the glycine trials involves a different drug.

In 19 treatment-resistant patients on clozapine 400 to 1,200 mg/day, adding glycine 30 g/day for 12 weeks did not reduce symptoms, while patients on clozapine alone had a 35% fall in positive symptoms; the authors suggested glycine may interfere with clozapine's effect [8]. A separate trial of 30 adults using 60 g/day for 8 weeks found no significant change in symptoms or thinking and no clinically significant worsening [9]. Both clozapine trials used doses 10 to 20 times the 3 g before-bed dose in the sleep study below, so they say little about supplement-level use [1][8][9].

The minoxidil labels do not list interacting drugs. They say not to use the product if you use other medicines on the scalp [4][5]. That wording concerns scalp products; oral glycine is not applied to the scalp.

What Glycine Does in the Studies That Exist

The clearest human data come from sleep research, not hair research. Healthy volunteers whose sleep was cut by about 25% for three consecutive nights took 3 g of glycine or placebo before bed. Glycine significantly reduced next-day fatigue on a visual analog scale, showed a tendency toward reduced sleepiness, and improved psychomotor vigilance test performance; plasma melatonin was unchanged [1]. This was not a trial in people with insomnia [1].

Glycine plus N-acetylcysteine (GlyNAC, 1:1) at 2.4, 4.8 or 7.2 g/day total for 2 weeks in 114 healthy older adults (mean age 65) was described as safe and well tolerated, but the primary endpoint, the glutathione redox ratio and total glutathione, did not rise against placebo across the whole group [7]. A 24-person trial of 16 weeks, 12 on GlyNAC and 12 on placebo, reported improvements in glutathione, oxidative stress and physical function; it was small and came from the group that developed GlyNAC [10]. Neither abstract reports side effects for glycine on its own [7][10].

What Topical Minoxidil 5% Is and How It Is Used

Topical minoxidil 5% is an over-the-counter hair regrowth product, not a prescription. The 2% solution switched from prescription to over-the-counter in 1996, and the 5% solution and 5% foam are both labeled over-the-counter [6].

The men's 5% solution label directs 1 mL with the dropper twice a day onto the top of the scalp, for men only, and states it is not intended for frontal baldness or a receding hairline [4]. The women's foam label directs half a capful once daily [5]. The men's label says using more or more often will not improve results, and that continued use is needed to keep regrowth or hair loss will begin again [4]. It says results may occur at 2 months and that some men need at least 4 months; the women's label says 3 months, and possibly 6 [4][5].

What the Minoxidil Labels Flag

Both the men's and the women's labels flag heart disease as a pre-use caution [4][5]. They say to stop use if any of these occur: chest pain, rapid heartbeat, faintness or dizziness; sudden unexplained weight gain; swelling of the hands or feet; scalp irritation or redness; unwanted facial hair growth. They also say to stop if there is no regrowth after 4 months (men's product) or 6 months (women's product) [4][5].

The labels also state the product is for external use only, should not be applied to other parts of the body, and contact with the eyes should be avoided. They say not to use it under age 18 or on a scalp that is red, inflamed, infected, irritated or painful, and to keep it away from fire, flame and smoking; the women's foam label calls the product extremely flammable. Both labels state the product may be harmful if used when pregnant or breast-feeding [4][5].

Does Glycine Help Hair Grow?

No trial has tested that. The hair-loss trials on this page tested minoxidil alone. In 393 men aged 18 to 49, 5% solution beat both 2% solution and placebo on nonvellus hair count over 48 weeks of twice-daily use, with more itching and local irritation at 5% [11]. In 381 women aged 18 to 49, 5% was superior to placebo on all three primary measures over 48 weeks, with more itching, irritation and hypertrichosis than 2% or placebo [12]. A 16-week trial of 352 men found 5% foam increased hair counts against placebo [13].

Timing

The topical minoxidil labels give application schedules (twice a day for the men's 5% solution, once a day for the women's foam) but no spacing interval for glycine [4][5]. The 3 g glycine dose in the sleep study was taken before bedtime, and that study did not test use with minoxidil [1].