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 resistance (TPR) and oxygen uptake (VO 2) during submaximal exercise. Design: The study was a prospective, longitudinal, double-blind, random crossover analysis of the cardiovascular and respiratory responses to a single bout of moderately intense exercise. Setting: Exercise tests were conducted in an exercise laboratory equipped with expired gas analysis and bioelectrical impedance cardiographic monitoring capabilities. Participants: Subjects were 18 (9 men, 9 women) volunteers (age = 29.5 ± 3.6yrs; weight = 70.7 ± 11.1kg), free from exercise-limiting pathology and rhinitis. Intervention: Each subject completed a maximal exercise tolerance test on the cycle ergometer followed by two randomly ordered submaximal exercise tests at a power output of 50% of the peak power attained on the maximal test: the first, 2 hours after ingesting 4mg of CM, the second, 2 hours after ingesting a placebo. The submaximal exercise tests lasted 20mm and data were recorded at 5, 10, 15, and 20mm of exercise during both the CM and placebo tests. Tests were completed approximately 48 hours apart. Results: Average VO 2 was 1,488 ± 367mL/min for the CM test and 1,477 ± 351mL/min for the placebo 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 were statistically similar. Conclusion: A single over-the-counter dose of CM does not alter TPR or VO 2 during submaximal exercise.