TLDR Two drugs, Minoxidil and Finasteride, can modestly maintain or regrow hair on the scalp's vertex with minimal side effects.
In 1999, two drugs were available for the treatment of balding in men: Minoxidil, a topical product available without a prescription in two strengths, and Finasteride, a prescription drug taken orally once daily. Both were modestly effective in maintaining and sometimes regrowing hair lost due to androgenic alopecia. The vertex of the scalp was most likely to respond to treatment, with little or no hair regrowth occurring on the anterior scalp or at the hairline. Side effects of these medications were minimal, making them suitable treatments for this benign but psychologically disruptive condition.
January 2022 in “Cosmoderma” Using oral minoxidil and dutasteride together can quickly increase hair growth and volume with minimal side effects.
March 2020 in “International Journal of Research in Medical Sciences” 
2 citations
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November 2015 in “Journal of cosmetology & trichology” Need better hair loss treatments beyond minoxidil, finasteride, and transplants.
5 citations
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January 2015 in “Journal of clinical & experimental dermatology research” MorrF improves hair growth better than minoxidil alone.
6 citations
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August 2012 in “PubMed” 
49 citations
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October 2009 in “Journal of the American Academy of Dermatology” Some people experienced hair loss after mesotherapy treatments for hair loss.
21 citations
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March 2005 in “PubMed” 
June 1996 in “Archives of Dermatology” Minoxidil, tretinoin, and finasteride may help hair regrowth in mild to moderate androgenetic alopecia.
55 citations
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February 1985 in “Archives of Dermatology” Minoxidil applied twice daily can help regrow hair in some people with hereditary baldness, with no serious side effects.
