my grandson was just prescribed vyvanese for adhd. He is 12 and one of the possible side effects can be an erection lasting up to 4 hours and be painful. How would i be able to tell my 12 year old this might happen but it probably wont. He def will not take it. And i was told to just start giving it to him tomorrow morn and send him to school. How embarassing would that be for him? I don t know if i can do it.