In the present study, myocardial infarction was induced experimentally in rats by isoprenaline injection. Circulating GOT, LDH, CPK, cAMP, Cortisol, pyruvate, lactate glucose and cardiac cAMP adenyl cyclase levels were gradually increased and serum and cardiac cAMP-PDE levels were gradually decreased from 1 hour to 120 hours after the first injection of isoprenaline. In the rats pretreated with ciplar (beta blocker) or Pushkarmula (indigenous drug) these changes were less when compared to untreated infarcted rats. Similar type of results were also observed in the infarcted rats post treated with Pushkarmula. The pretreatment with Pushkarmula was found to be more effective than post treatment which gives a preventive and curative bearing of the drug in myocardial infarction.