Kirkland Signature Extra Strength for Men Minoxidil Topical Solution USP, 5% Hair Regrowth Treatment regrows more hair than 2% Minoxidil Topical Solution. Results may occur at 2 months. Kirkland Signature Extra Strength for Men Minoxidil Topical Solution USP, 5% Hair Regrowth Treatment is for men who have a general thinning of hair on the top of the scalp. Not intended for frontal baldness or a receding hairline. Some people may experience a dry, itchy scalp and irritation.