Isoprenaline Hydrochloride

ADMINISTRATION ROUTES:

IV

ALTERNATIVE NAMES:

Isuprel

ICU INDICATIONS:

1. Bradycardia

Note: current international guidelines do not recommend isoprenaline as the first line agent to treat any condition

PRESENTATION AND ADMINISTRATION:

IV:

Isoprenaline 1 mg in 5 mL (1:5000) vials

For IV infusion, add 1 mg to total volume of 50 mL of compatible IV fluid. Administer at 0 - 60 mL/hr (0 - 20 mcg/min)

Compatible with the following IV fluids: Normal saline, glucose and sodium chloride, 5% glucose, Hartmanns

Does not require refrigeration. Do not freeze. Protect from light and air. Discard any diluted fluid not used within 24 hours of preparation. Do not use solution if pinkish or brown in colour or contains precipitate.

DOSAGE:

IV infusion:

Commence at 0.5 - 5 mcg/min ( 1.5 - 15 mLs/hr)

Doses 20 mcg/min (60 mL per hour) or greater have been used by infusion.

IV bolus:

Dilute 200 mcg in 20 mL and give 10 mcg (1 mL) bolus

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

Dose as in normal renal function

DOSAGE IN PAEDIATRICS:

IV infusion:

300 mcg/kg in 50 mL of compatible IV fluid

Commence infusion at 0.1 mcg/kg/min (1 mL/ hr) & titrate to effect

CLINICAL PHARMACOLOGY:

Isoproterenol hydrochloride is a synthetic sympathomimetic amine that is structurally related to epinephrine but acts almost exclusively on beta receptors.

CONTRAINDICATIONS:

1. Heart block caused by digitalis intoxication
2. Known hypersensitivity to isoprenaline

WARNINGS:

Potential for worsening of cardiac function

Isoprenaline, by increasing myocardial oxygen requirements while decreasing effective coronary perfusion, may have a deleterious effect on the injured or failing heart.

Worsening of heart block

In a few patients, presumably with organic disease of the AV node and its branches, isoprenaline has paradoxically been reported to worsen heart block or to precipitate Stokes-Adams attacks during normal sinus rhythm or transient heart block.

Contains sulfite

Contains sodium metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people.

PRECAUTIONS:

General:

Isoprenaline should generally be started at the lowest recommended dose. This may be gradually increased if necessary while carefully monitoring the patient. Doses sufficient to increase the heart rate to more than 130 beats per minute may increase the likelihood of inducing ventricular arrhythmias. Such increases in heart rate will also tend to increase cardiac work and oxygen requirements which may adversely affect the failing heart or the heart with a significant degree of arteriosclerosis.

Particular caution is necessary in administering isoprenaline to patients with coronary artery disease, coronary insufficiency, diabetes, hyperthyroidism, and sensitivity to sympathomimetic amines.

Laboratory Tests:

No tests in addition to routine ICU tests are required

Drug/Laboratory Test Interactions:

None noted

IMPORTANT DRUG INTERACTIONS IN ICU:

Isoprenaline and adrenaline should not be administered simultaneously because both drugs are direct cardiac stimulants and their combined effects may induce serious arrhythmias.

Beta receptor blocking agents and isoprenaline inhibit the effects of each other.

ADVERSE REACTIONS:

CNS:

Nervousness, headache, dizziness

Cardiovascular:

Tachycardia, palpitations, angina, Stokes-Adams attacks, pulmonary oedema, hypertension, hypotension, ventricular arrhythmias, tachyarrhythmias

Other:

Flushing of the skin, sweating, mild tremors, weakness