Calcium channel blockers and the CVS reflex responses during lower body suction.
Nine normal men (mean age 27.6 yr) were exposed to continuous lower-body suction pressure (LBSP) of -20 to -50 mmHg (for 5 min at each level) on four different occasions after having consumed a single oral therapeutic dose of either diltiazem, nifedipine, verapamil, or a placebo, randomly, in a single blind manner. The suction was applied at 12.30 pm in all experiments, while the medications were administered in such a manner so that their expected peak plasma levels would have been achieved at the time of suction application. The cardiovascular reflex effects commenced at a pressure of -30 mmHg, and peaked at -50 mmHg. The increases in the heart rate for all treatments at -50 mmHg was statistically similar (about 16-20 beats/min). The systolic BP fell by about 9 mmHg for the placebo experiments, and this change was not different from the changes produced by the 3 Calcium channel blocker treatments. The diastolic BP increase was about 3 mmHg. The Cardiac index did not vary significantly. Our results suggest that the commonly used Ca++ channel blockers do not adversely affect orthostatic tolerance.
Dikshit
M B
MB
Department of Physiology, Armed Forces Medical College, Pune.
Lavania
A K
AK
Devdikar
A R
AR
Prasad
B A
BA
Jog
N V
NV
Ganguly
S S
SS
D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002320:Cardiovascular Physiological Phenomena; D002319:Cardiovascular System / Q000187:drug effects*; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D010812:Physical Stimulation; D012018:Reflex / Q000187:drug effects* / Q000502:physiology; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology
D002121:Calcium Channel Blockers