NONPRESCRIPTION CHLORPHENIRAMINE MALEATE AND SUBMAXIMAL EXERCISE RESPONSES

Objective: To determine if a single, over-the-counter dose of the H-1 antagonist chlorpheniramine maleate (CM) alters total peripheral resis tance (TPR) and oxygen uptake (VO2) during submaximal exercise. Design : The study was a prospective, longitudinal, double-blind, random cros sover analysis of the cardiovascular and respiratory responses to a si ngle bout of moderately intense exercise. Setting: Exercise tests were conducted in an exercise laboratory equipped with expired gas analysi s and bioelectrical impedance cardiographic monitoring capabilities. P articipants: Subjects were 18 (9 men, 9 women) volunteers (age = 29.5 +/- 3.6yrs; weight = 70.7 +/- 11.1 kg), free from exercise-limiting pa thology and rhinitis. Intervention: Each subject completed a maximal e xercise tolerance test on the cycle ergometer followed by two randomly ordered submaximal exercise tests at a power output of 50% of the pea k power attained on the maximal test: the first, 2 hours after ingesti ng 4mg of CM, the second, 2 hours after ingesting a placebo. The subma ximal exercise tests lasted 20min and data were recorded at 5, 10, 15, and 20min of exercise during both the CM and placebo tests. Tests wer e completed approximately 48 hours apart. Results: Average VO2 was 1,4 88 +/- 367 mL/min for the CM test and 1,477 +/- 351 mL/min for the pla cebo test. TPR was 12.3 +/- 7.4PRU for the CM and 11.3 +/- 4.5PRU for the placebo tests. Analysis of variance revealed that these scores wer e statistically similar. Conclusion: A single over-the-counter dose of CM does not alter TPR or VO2 during submaximal exercise. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Acad emy of Physical Medicine and Rehabilitation.