Unable to orgasm/ejaculate properrly (erectile dysfunction) viagra,cialis etc.....?

What is the best drug for erectile dysfunction.I am on a medication causing me not to fully properly being able to orgasm -ejacualte as it's one of the side effects of risperidone.what drug would actually help this problem whilst still on risperidone.Does anybody have any experienceces on being on an erectile dysfunction medication and do they work and how ell?(sucha as viagra ,cialis etc.....)aslo I was wondering -can you buy viagra,cialis etc..... in shops in the uk?