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Vial $5.38, Tablet $0.06

Metoprolol

Editor: Updated Class:

ADMINISTRATION ROUTES:

PO, NG, IV

ALTERNATIVE NAMES:

Lopressor, Betaloc, Metoprolol CR

ICU INDICATIONS:

  1. Hypertension
  2. Acute myocardial infarction
  3. Secondary prevention in patients with coronary artery disease
  4. Angina
  5. Rate control (including supraventricular & ventricular arrhythmias)

PRESENTATION AND ADMINISTRATION:

PO / NG:

Tablets:

Lopressor 50 mg tablets (pink), Lopressor 100 mg tablets (light blue)

Controlled Release tablets:

Betaloc CR 23.75mg, 47.5mg, 95mg and 190 mg tablets (white to off white)

Oral Suspension:

Metoprolol suspension 1 mg/mL

Note: Do not crush controlled release (CR) tablets for NG administration. Only short/immediate acting tablets can be administered (crushed) down a nasogastric tube

IV:

Betaloc 5 mg/5 mL vial

Inject undiluted solution at a rate of 1-2 mg/min; usual maximum dose 10 mg. Compatible with the following IV fluids: Normal saline, 5% or 10% glucose, Glucose and Sodium Chloride

DOSAGE:

PO/NG:

Immediate release

25 - 100 mg TDS or BD

PO only:

Controlled release (CR)

23.75 - 190 mg OD

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose in renal impairment

GFR (ml/min) DOSE
<10 start with small doses & titrate
10-20 start with small doses & titrate
>20-50 dose as in normal renal function

Dose in renal replacement therapy

MODALITY DOSE
CAPD start with small doses & titrate
HD start with small doses & titrate
CVVHDF start with small doses & titrate

DOSAGE IN PAEDIATRICS:

IV:

0.1 mg/kg over 5 minutes

PO:

1 - 2 mg/kg QID to BD

CLINICAL PHARMACOLOGY:

Metoprolol is a beta-adrenergic receptor blocking agent. In vitro and in vivo animal studies have shown that it has a preferential effect on beta1 adrenoreceptors, chiefly located in cardiac muscle. This preferential effect is not absolute, however, and at higher doses, metoprolol also inhibits beta2 adrenoreceptors, chiefly located in the bronchial and vascular musculature.

CONTRAINDICATIONS:

  1. Sinus bradycardia
  2. Heart block greater than first degree
  3. Cardiogenic shock
  4. Overt cardiac failure
  5. Asthma

WARNINGS:

Cardiac Failure

Sympathetic stimulation is necessary in supporting circulatory function in congestive heart failure, and beta blockade carries the potential hazard of further depressing myocardial contractility and precipitating more severe failure.

Discontinuation of therapy

Discontinuation of therapy in a patient with coronary artery disease may lead to rebound angina, arrhythmia or myocardial infarction.

Diabetes and Hypoglycaemia

Beta blockers may mask tachycardia occurring with hypoglycaemia.

Thyrotoxicosis

Beta-adrenergic blockade may mask certain clinical signs (such as tachycardia) of hyperthyroidism. Abrupt withdrawal of beta blockade may precipitate a thyroid storm.

PRECAUTIONS:

General:

Metoprolol may aggravate peripheral arterial circulatory disorders

Laboratory Tests:

No tests in addition to routine ICU tests are required

Drug/Laboratory Test Interactions:

None known

IMPORTANT DRUG INTERACTIONS IN ICU:

Beta blockers may exacerbate the rebound hypertension which can follow the withdrawal of clonidine

ADVERSE REACTIONS:

Body as a Whole:

Tiredness, fatigue

Cardiovascular System:

Bradycardia, cold extremities, hypotension, leg pain

Respiratory System:

Wheeziness, dyspnoea

Digestive System:

Diarrhoea, nausea

Nervous System:

Dizziness, vertigo, light-headedness