my partner has a sprcit for 10mg but it doesn't always do the trick. however 20mg is too much for him. So he takes 1 1/2 and it's perfectly fine. it varies for everyone and depends on the level of ED that he expericences. Make sure he tell the doc that one isn't doing the trick. The dr. may just want to change the dosage level or even switch him to cialis or viagra to see what works better for him. good luck.