It is not only dangerous after extended use. If taken in a large dose, ipecac can kill you the very first time you use it. It is a poison which induces vomiting. Before you take it, you are supposed to call your Poison Control Center and use only when the Poison Center or your doctor directs you to use it. Some poisons should NOT be removed by vomiting. It is designed to be used only in life/death situations, since it itself can kill.
Karen Carpenter died due to of complications from anorexia nervosa, specifically "cardio toxicity" brought on by the chemical emetine. Experts now agree that the only way she could have had emetine in her system was if she had misused ipecac.
source:http://www.leadsister.com/articles/kcarticles.html