There are a number of possible metoprolol side effects, it is best to speak to your doctor about these and consult with him/her should any of these persist and become bothersome. Metoprolol tartrate is a selective beta 1-adrenoreceptor blocking agent, available as 25 mg, 50 mg, and 100 mg tablets for oral administration. The most common side effects of metoprolol are dizziness, constipation, diarrhea, dry mouth, gas, headache, heartburn, lightheadedness, drowsiness, muscle aches, nausea, and trouble sleeping. More. Taking metoprolol 25 mg tablets can cause some more common serious side effects that affect how your body functions. This medication changes how your heart beats, so it can have a range of effects. Metoprolol side effects: Along with its needed effects, Metoprolol may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Side Effects. Drug information provided by: IBM Micromedex. Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Lopressor (metoprolol tartrate) Tablets and Injection is a selective beta-adrenoreceptor blocking agent (beta-blocker) used to treat high blood presure (hypertension), angina, and heart attacks. Find information about common, infrequent and rare side effects of Metoprolol Succinate Oral. Along with its needed effects, metoprolol may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Although not all of these side effects may occur, if they do occur they may need medical attention. Learn about side effects, warnings, dosage, and more. Metoprolol oral tablet is a prescription medication used to treat high blood pressure, chest pain, and heart stress after a heart attack. It's.