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HISTAMINE RECEPTOR BLOCKADE DOES NOT INCREASE CREATINE KINASE CONCENTRATIONS FOLLOWING MUSCLE DAMAGING EXERCISE

Abstract

Case studies have documented the use of antihistamines in the hours preceding extensive and unaccustomed exercise that resulted in rhabdomyolysis. Histamine is a known mediator of inflammation caused by tissue damage. It is unknown if blockade of histamine actions during and immediately following muscle damaging exercise increases the severity of injury. PURPOSE: Therefore, the purpose of this experiment was to determine if histamine receptor blockade during muscle damaging exercise affected the extent of injury. It was hypothesized that blockade of histamine H1 + H2 receptors would increase muscle damage as evidenced by a higher creatine kinase (CK) concentration in the ensuing 72 hours in a histamine blockade group compared to a control group. METHODS: Volunteers (n=20, 4F) were randomly assigned to histamine blockade (n=10; 540mg fexofenadine; an H1 blocker and 300mg ranitidine; an H2 blocker) or control (n=10; no drug) group. Muscle damage was induced by 45-min of downhill running (-10% grade) at a heart rate of ~150 BPM. Blood collected prior to, following, 6, 12, 24, 48, and 72 hours after exercise was analyzed for CK concentrations. Comparison between groups and over time were determined by an unpaired repeated measures ANOVA with a significance value set at p<0.05. RESULTS: CK concentrations for both groups increased immediately following exercise (mean ± SE; 25.2 ± 4.8 u/L), as well as 6 (48.7 ± 6.9 u/L), 12 (62.2 ± 8.1 u/L), 24 (52.5 ± 8.4 u/L), and 48 (30.0 ± 5.0 u/L) hours over the pre-exercise concentrations (17.3 ± 3.3 u/L) (p<0.05). Although there was a slight increase in CK concentrations in the blockade group compared to the control group at 12, 24, 48 and 72 hours, the mean difference between groups (5.0 ± 10.1 u/L) was not significant. CONCLUSION: Thus, it appears that histamine receptor blockade does not increase the magnitude of muscle damage following moderate intensity eccentric aerobic exercise.

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