Metoprolol tartrate

How it works

It selectively blocks cardiac beta-1 adrenoceptors, reducing heart rate, contractility and atrioventricular conduction, thereby lowering cardiac workload, blood pressure and myocardial oxygen demand.

Prescribing in practice

• It should not be stopped abruptly, as sudden withdrawal can precipitate rebound tachycardia, worsening angina or myocardial infarction; doses should be tapered.
• Because the tartrate salt is short-acting it usually requires more frequent dosing than the modified-release succinate form, and the two are not interchangeable on a milligram-for-milligram basis.
• Beta-1 selectivity is relative and is lost at higher doses, so caution is needed in bronchospastic disease, and it can mask the warning signs of hypoglycaemia in diabetes.

Monitoring

Monitor heart rate and blood pressure for therapeutic effect and for excessive bradycardia or hypotension, particularly during dose titration.

Counselling the patient

• Do not stop this medicine suddenly; your doctor will reduce the dose gradually if it needs to be stopped.
• It may cause tiredness, cold hands and feet, or a slow pulse; report a very slow heartbeat or fainting.
• If you have diabetes, be aware it can hide some warning signs of low blood sugar such as a fast heartbeat.

Evidence & guidelines

Beta-blockers such as metoprolol are established agents in NICE guidance for angina and rate control of arrhythmias; mortality benefit in chronic heart failure is best evidenced for the modified-release succinate formulation.