MONA is a mnemonic standing for Morphine, Oxygen, Nitrates, and Aspirin, historically used to summarise the immediate initial management of acute coronary syndrome (ACS), including unstable angina, NSTEMI, and STEMI.
Aspirin (300mg, chewed) is the most evidence-based component and remains standard first-line treatment for all acute coronary syndromes: it inhibits platelet aggregation and reduces thrombus formation at the site of plaque rupture. Nitrates (sublingual or spray glyceryl trinitrate, GTN) dilate coronary arteries and reduce cardiac workload, relieving ischaemic chest pain. Oxygen was historically given routinely, but current guidelines recommend giving supplemental oxygen only to patients with oxygen saturations below 94%; giving high-flow oxygen to patients with normal saturations is not beneficial and may cause harm.
Morphine for pain relief in ACS has become more controversial. While it remains an option for severe uncontrolled chest pain, observational evidence raised concerns that it may slow the absorption and reduce the effectiveness of antiplatelet agents including aspirin and P2Y12 inhibitors such as ticagrelor. Current guidelines therefore recommend morphine with caution and titrated to the minimum effective dose, rather than as a routine first treatment.
Modern ACS management goes well beyond MONA and is guided by risk stratification, biomarkers, ECG findings, and rapid access to the catheterisation laboratory for reperfusion. MONA remains a useful aide-memoire for initial emergency response, but the nuances in its application reflect how evidence-based cardiology has evolved since the mnemonic was first introduced.
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