Side effects are quite rare, and ALMOST (read: not always) invariably reversible in the event they occur. Alternatives exist, but they aren't necessarily a GOOD alternative. I've heard that L-Arginine can have a similar effect, but this is all speculation from internet alchemists. The only PROVEN treatments are Minoxidil and Finasteride in the hair loss battlegrounds.
Topical spironolactone might be able to help you, but it's inconvenient to apply, and has a way of turning your pillow different colors and making it smell kinda funky. Copper peptide topical lotions might help as well.
I don't advocate any of these however. I'm a religious man, but I prefer science over faith in the medicinal area.
Good luck to you though.