Not Medical Advice: Pill imprint M 18 has been identified as Metoprolol tartrate 25 mg.
Metoprolol tartrate is used for:
Treating high blood pressure, alone or with other medicines
Long-term treatment of chest pain
Reducing the risk of death because of heart problems in patients who have had a heart attack. It may also be used for other conditions as determined by your doctor.
Metoprolol tartrate is a beta-adrenergic blocking agent (beta-blocker). It works by reducing the amount of work the heart has to do (reduces chest pain) and the amount of blood the heart pumps out (lowers high blood pressure). It is also used to stabilize the heart rhythm in conditions in which the heart is beating too fast or in an irregular rhythm.