The pendulum never seems to stop swinging when it comes to the efficacy of epinephrine in cardiac arrest.
20-25 years ago, the push was to use escalating doses of epinephrine starting at 1 mg and increasing to 3 mg, then 5 mg, and continuing at 5 mg as needed. Some protocols started directly with 5 mg and continued with 5 mg thereafter. These protocols were based on early studies which suggested that higher doses of epi resulted in improved survival to hospital admission.
Subsequent analyses, 5-10 years later, showed that many of the people who got high doses of epi were dying at the same rate, or perhaps even higher rate. Also, amongst the survivors, the neurologic outcome was worse.
Over the past few years, a few studies have reported that epi, even in 1 mg doses, could be potentially harmful and not helpful.
The most recent literature seems to be coming back to a middle zone whereby there probably is some benefit to epinephrine, but only if given in a certain time period. These studies suggest that epi is most beneficial if given in the first 15-20 minutes after cardiac arrest. Continued dosing of epi beyond the 20 minute mark (post cardiac arrest) seems to produce more rapid deterioration and is not supported by the literature.