Q: If Rogaine is used only once a day will it still be effective? — I.P., Hempstead, Long Island, NY
A: Once a day topical use of Rogaine (topical minoxidil 2% and 5%) is probably almost as effective as using it twice a day. The reason is, although minoxidil has a relatively short half-life of several hours when given orally, when topically applied, it has a half-life of 22 hours in the skin.
This suggests that once-a-day dosing is a reasonable option. It is important to realize that Pfizer, the company that now makes Rogaine, specifically states that it will be less effective if used only once a day.
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