Pharmacology

Metoprolol

Metoprolol (Lopressor) is a selective beta-1 receptor blocker used primarily to decrease heart rate (chronotropy) and cardiac contractility (inotropy) in those with anginal chest pain, acute myocardial infarctions, supraventricular tachycardias, and even off-label for anxiety disorders.

As a cardiac anesthesiologist, I use short acting agents almost exclusively (ie, esmolol), but if I feel that a patient’s clinical condition warrants longer acting beta blockade without negatively affecting their operative care (ie, upcoming blood loss/hypotension), I’ll certainly consider IV metoprolol.

As an intensivist, I use metoprolol tartrate as either an intravenous or enteral medication fractionated every 6 hours. For outpatients, this medication is usually written as twice a day (twice for tartrate) or as a daily medication for metoprolol succinate (Toprol XL, single for succinate). Rate controlling atrial fibrillation is perhaps one of the most common indications I encounter in the ICU.

In general, I don’t consider pure beta blockers like metoprolol to be great antihypertensives. Remember mean arterial pressure is related to stroke volume (preload, afterload, contractility), heart rate, and rhythm. I evaluate a patient’s entire clinical picture to determine which variables are likely contributing to hypertension – if I think it’s related to vascular resistance being high, for example, then I’m more likely to prioritize afterload reduction (calcium channel blockers, mixed alpha/beta blockers, better pain control, etc.)

Drop me a comment below with questions! 🙂

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