I started suboxone today and now i feel drowsy and itchy. what can i do for that?

Lower the dose: All opioids can cause release of histamine, which can result in feeling itchy. As long as you don't have hives or problems breathing, you can just use a mild antihistamine. The non-sedating ones produce less drowsiness (claritin, zyrtec etc.) but don't work as well as Benadryl (diphenhydramine) and other older ones. Talk to your doctor about lowering the dose if it persists.