Spironolactone
"I was a sufferer real bad of adult acne on my back, chest and chin, and this was the only thing that worked for me. Unfortunately I suffered a drug reaction from it that left my lower extremities (rectal itch, etc) that kept me up all night....it was horrible and it took a few months for it to subside with a lower dosage and antihistamines. Lower dosage worked better but it did eventually did damage to my kidneys which is a risk side affect of taking this drug. So be aware if you have weak kidneys DO NOT take this drug!"