Prolongation of simple and choice reaction times in a double-blind comparison of twice-daily hydroxyzine versus terfenadine.

Newer, nonsedating antihistamines provide a therapeutic alternative for the patient with allergy whose work is impaired by the side effects of traditional H1 antihistamines. To assess the differential effect of these antihistamines on reaction times and subjective symptoms, we compared terfenadine, 60 mg twice daily, to hydroxyzine, 25 mg twice daily, in a double-blind, placebo-controlled, crossover study of 16 healthy, asymptomatic adults. Simple reaction time and choice reaction time were measured with a computer-based, eye-hand, reaction-time testing apparatus. Reaction times and symptom scores were assessed 90 minutes after the fourth and tenth doses of each drug. Hydroxyzine, but not terfenadine, significantly prolonged both simple and choice reaction time (p less than or equal to 0.0001). However, decision time, the time to process one bit of spatial information, was not prolonged by either antihistamine. Therefore, hydroxyzine prolonged the interpretation and response to stimuli of the central nervous system without increasing single-bit processing time. Although terfenadine was not different from placebo for any symptom assessed, hydroxyzine produced significant drowsiness (p = 0.001), dry mouth (p = 0.022), and irritability (p = 0.021). During the 5 days of hydroxyzine administration, neither objective nor subjective symptoms demonstrated the development of tolerance. No correlation was found between subjective symptoms and prolongation of reaction times by hydroxyzine, suggesting that side effect symptoms of traditional antihistamines are unreliable predictors of objective performance. Terfenadine provides a promising therapeutic alternative to traditional antihistamines for individuals performing critical tasks.

Severe systemic reaction to diphosphonate bone imaging agents: skin testing to predict allergic response and a safe alternative agent.

We describe a severe systemic reaction which occurred in a patient on two occasions after i.v. injection of chemically related diphosphonate bone imaging agents. Skin testing showed reactivity to multiple commercially available diphosphonate compounds but no significant response to pyrophosphates. A subsequent pyrophosphate bone scan resulted in no adverse reaction. Severe systemic reactions to diphosphonates can occur, skin testing may prove useful in evaluating allergic reactions, and pyrophosphates appear to be a safe alternative agent in patients proven or suspected allergic to diphosphonates.