you never want to take someone else's medication; this is risky and not safe. antibiotics do not help with poison ivy. i would recommend calling your local hospitals to see if they have a clinic or try visiting the "in-store clinics" that are in some drugstores. you can try products like zanafel ivy dry and tecnu that can help with drying up the oils causing the itching.
i have a sinus infection poison ivy and no insurance. a friend gave me a sulfameth/tmp ds prescription. will this help?