Fever induced by labetalol.

Fever caused by beta-adrenoceptor blocking agents is rare. We describe fever in two patients who had been treated with labetalol. In both patients, two challenge periods were rapidly followed by a relapse, whereas on each occasion there was normalization of temperature after discontinuation of the drug therapy. This reaction is rare and unpredictable. Because there was a clear sensitization period of three to four weeks, dose independency, and an accelerated reaction to rechallenge, this adverse effect seems to be caused by an immunoallergic reaction.