related to the alpha- adrenergic blocking effects of clonidine. These side effects are dose-related, typically decrease over time, and mostly affect the nervous system, cardiovascular system , and the gastrointestinal system. REFERENCE + Evaluation of clonidine hydrochloride (catapres): a new antihypertensive agent. Kosman ME JAMA 1975;233:174-6. Is clonidine an effective smoking