EFFECTS OF M-NIFEDIPINE AND NIFEDIPINE GI VEN INTRADUODENALLY ON CORONARY FLOW, MYOCARDIAL OXYGEN, AND CARBON-DIOXIDE METABOLISM IN DOGS

In anesthetized dogs intraduodenal administration. of m-nifedipine (m- Nif ) 0.4 mg . kg-1, coronary flow increased from 708 +/- 72 to 880 +/ - 150 ml . min-1 . kg-1 (+24%) at 5 min, to 1976 +/- 350 ml . min-1 . ks-1 (+179%) at 30 min, and to 998 +/- 250 ml . min-1 . kg-1 (+41%) at 4 h. At the dose of nifedipine (Nif), coronary flow increased from 77 8 +/- 91 to 1080 +/- 90 ml . min-1 . kg-1(+39%) at 3 min and to 1836 /- 280 ml . min-1 . kg-1(+136%) at 90 min. m-Nif was more 43% potent t han Nif and the duration of action of m-Nif was longer. m-Nif reduced heart rate by -39%, while Nif reduced only -11%. m-Nif increased coron ary sinus O2 content and reduced MVO2, and no difference was seen betw een these 2 drugs. However, the rate Of CO2 production with m-Nif was reduced to a greater degree than that of Nif. The results indicated th at m-Nif was more beneficial in alleviating myocardial ischemia than t hat of Nif.