I've used Trisoralen lots of times. You take 2 pills 1 hour before tanning and it will accelerate your tanning greatly. Not useful anymore since several years ago these 6 min 'turbo' tanning beds came out.
trisoralan makes you dark as all hell if you are even mildly tan. My ghost white friend got decently brown using it. the melanin effect seems to be permanent, though you still fade.
I freind of mine got his doc to prescribe him some tanning pills, I don't know what kind but he said that he was going on a cruise for 2 weeks and he didn't want to get sunburned. So the doc gave him these pills and told he to use them and tan before he leaves