P's and blues: potentiation of propoxyphene withdrawal by a variety of antihistamines.

Three cases are presented of patients who experienced potentiation of propoxyphene's effects by different antihistamines. These included increased analgesia and mild euphoria as well as moderately severe symptoms of opiate withdrawal at therapeutic doses of propoxyphene. In one case, withdrawal symptoms were blocked with clonidine, an alpha-2 agonist. Since the specific antihistamine-opiate combination, pentazocine and tripelennamine, is associated with increased lethality, physicians are cautioned to avoid combining propoxyphene with antihistamines.