Hello. I m Dr. Christensen. I m sorry your brother is having problems. This is a potentially explosive situation that should be addressed immediately. As you know, Vyvanse is a form of amphetamine, so the abuse potential for this medication is high. Your brother is clearly overusing his prescription, and when he runs out he is exhibiting classic withdrawal symptoms. When used for long periods of time (weeks or more), amphetamines can reduce both libido (sex drive) and fertility in males. Obviously, this could present some difficulties for a couple hoping to conceive. However, the greater problem at this point is not whether your brother can father a child; of more concern is his amphetamine abuse and addiction, which will significantly impair his ability to PARENT a child. I suspect you already know what needs to be done for your brother. He needs help with his substance abuse problem. His first step should be to contact the physician who prescribed his Vyvanse and discuss his situation with that provider. Unfortunately, many addicts are hesitant to approach doctors whom they see as a potential source of medications. Therefore, it may be up to you and the remainder of the family to urge him in the appropriate direction. If that doesn t work you might consider calling an ambulance the next time he develops withdrawal symptoms. Ultimately, you may have to report his potentially dangerous behavior to the legal authorities. (Unfortunately, addicts occasionally harm their loved ones when they re in the throes of withdrawal or when they re drug-seeking; choking a family member could easily escalate into something even more violent.) I hope that answers your question, and I hope things go well.