ADMINISTRATION ROUTES:
PO, NG, IV
ALTERNATIVE NAMES:
Lopressor, Betaloc, Metoprolol CR
ICU INDICATIONS:
- Hypertension
- Acute myocardial infarction
- Secondary prevention in patients with coronary artery disease
- Angina
- 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:
- Sinus bradycardia
- Heart block greater than first degree
- Cardiogenic shock
- Overt cardiac failure
- 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