Remember MONA (morphine, oxygen, nitro, aspirin) from med school? Well, she may be just “A” now….
Over the years, all of these treatments (except for good old aspirin) have become somewhat controversial in the treatment of ACS.
Let’s focus on morphine today. Morphine’s obvious benefit is its ability to control pain and therefore decrease sympathetic tone. It has also been proposed that this medication may cause coronary vasodilation and decrease myocardial oxygen demand.
The support behind morphine for ACS began to waver after a large, retrospective trial was published suggesting that patients with ACS who had received morphine had a higher mortality risk (the CRUSADE initiative), though at the time, the authors did not seem to have a good answer for why this was the case. Additionally, it’s important to note that this was a retrospective trial, and not randomized nor blinded.
Then, a few studies were done following CRUSADE and found that morphine had an effect on antiplatelet agents commonly used in conjunction with aspirin (such as clopidogrel, or Plavix). These studies concluded that morphine seemed to slow the onset time or reduce the concentration of anti-platelet agents. But the studies were limited by their small size and inclusion of healthy subjects.
To this date, there have been no randomized controlled trials evaluating this question. There have been, however, a number of larger observational trials that showed mixed results regarding morphine and adverse events, but there’s no final verdict yet.
So, at this point, the benefit (or harm, for that matter) of morphine use in ACS remains unclear. Many experts now recommend avoiding it and using alternative treatments until a more definitive conclusion has been reached. Sine the CRUSADE initiative, the AHA guidelines have changed their recommendation of morphine for analgesia to a class IIb (basically, “may be considered” but more studies are needed).
Tl;dr: Use morphine with caution in patients with ACS. At this point, we need more research looking into whether morphine truly interacts with anti-platelet agents, but if you can use another agent, go for it.