I accidentally tried a formula which till today still works for me well if I can have a chick overnight.
Not so long ago, I went to have lunch at Geylang Lor Bak Chor turtle soup (don know the coffee shop name), order a medium size turtle soup with rice.
At night went to have supper with my friends, ate Bak Kut teh and ordered one big bottle of Guiness Stout.
That was it, the whole night my erection would not go down, I didn't have a gal with me so I had to self service 3 times to be able to go to sleep!
Then I thought it was a fluke, so I tested it again. But this time I met a PRC studying in a language centre here and I bonk her until she cry tolong and wet the whole bed in hotel 81.
This method is safe and don't think there is any risk of banned substance. Hope it works for you guys.