Mexohar (mexiletine 50 mg) and Seloken XL (metoprolol succinate 25 mg) can be used together in selected patients with certain cardiac arrhythmias only when prescribed by a cardiologist, but this combination requires careful clinical assessment and monitoring because it can increase the risk of excessive slowing of heart rate, low blood pressure, dizziness, or conduction disturbances. The decision is strictly individualised based on ECG findings, underlying heart disease, pulse rate, blood pressure, and overall cardiac risk profile, and it must be used only under specialist supervision with appropriate follow up. It is not safe for self use, self initiation, or dose adjustment without medical guidance.