Nioxin Hair Regrowth Treatment Minoxidil topical solution USP 5% is for men who have a general thinning of hair on the top of the scalp (vertex only). Not intended for frontal baldness or a receding hairline. Minoxidil topical solution USP 5% has been shown to regrow hair in men with the following degrees of thinning hair or hair loss. If men have more hair loss or hair loss in a place different than the vertex, minoxidil topical solution USP 5% may not work. For best results apply directly to scalp twice daily.