ADMINISTRATION ROUTES:
Intravenous
ALTERNATIVE NAMES:
Isuprel, Isoproterenol
ICU INDICATIONS:
- Bradycardia with or without heart block
Note: current international guidelines do not recommend isoprenaline as the first line agent to treat any condition
PRESENTATION AND ADMINISTRATION:
INTRAVENOUS:
Isoprenaline 1 mg in 5 mL (200 micrograms/mL) vials
Store the undiluted product at room temperature and protect from light and air. The isoprenaline solution is normally clear. Do not use it if it is pink or brownish in colour or if it contains a precipitate. Discard any unused portion immediately.
Compatible with the following intravenous fluids:
- Glucose 5%
- Sodium chloride 0.9% may be used in case of clinical need. Do not use routinely as this solution is less stable
Central line preferred. If unavailable, peripheral line may be used.
The infusion has a low pH and extravasation is likely to cause venous irritation and tissue damage. If given peripherally, use a large vein with monitoring for phlebitis.
Intravenous continuous infusion:
Add 1 mg (5 mL) to 45 mL of compatible fluid in a syringe to make a final volume of 1 mg in 50 mL (20 micrograms/mL)
Administer as a continuous infusion according to prescription
Discard any unused portion of the vial immediately
Discard any unused solution within 24 hours of preparation
DOSAGE:
Intravenous continuous infusion:
Start at 5 micrograms/min (15 mL/h)
Titrate every 5 minutes to effect up to 20 micrograms/min (60 mL/h)
DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:
Dose as in normal renal function
DOSAGE IN LIVER FAILURE:
Dose as in normal liver function
DOSAGE IN PAEDIATRICS:
Intravenous continuous infusion:
Prepare 300 micrograms/kg in 50 mL of compatible IV fluid
Start infusion at 0.1 micrograms/kg/min (1 mL/h)
Titrate to effect
CLINICAL PHARMACOLOGY:
Onset of Action: Immediate
Duration of Action: 10 - 15 minutes
Elimination: 15 - 25 minutes after stopping the infusion
Isoprenaline hydrochloride is a synthetic sympathomimetic amine that is structurally related to epinephrine but acts almost exclusively on beta receptors so has marked chronotropic and arrhythmogenic effects. It also causes peripheral vasodilation and has a bronchodilatory action. Elimination is entirely via liver metabolism.
CONTRAINDICATIONS:
- Heart block caused by digitalis intoxication
- Known hypersensitivity to isoprenaline
- Recent myocardial infarction
- Tachyarrhythmias
- Phaeochromocytoma
WARNINGS:
Potential for worsening of cardiac function: Isoprenaline may increase myocardial oxygen requirements while decreasing effective coronary perfusion. This may worsen failure in an injured 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 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.
Hypovolaemia should be corrected before starting treatment.
Particular caution is necessary in administering isoprenaline to patients with coronary artery disease, coronary insufficiency, diabetes, hyperthyroidism, and sensitivity to sympathomimetic amines.
Avoid abrupt discontinuation unless a pacemaker has been fitted.
Laboratory Tests:
No laboratory tests are required in addition to routine ICU monitoring.
Drug/Laboratory Test Interactions:
None known
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.
Monoamine oxidase inhibitors may magnify the effect of isoprenaline.
ADVERSE REACTIONS:
General:
Flushing of the skin, sweating, mild tremors, weakness
Cardiovascular:
Tachycardia, palpitations, angina, Stokes-Adams attacks, pulmonary oedema, hypertension, hypotension, ventricular arrhythmias, tachyarrhythmias
Neurological:
Nervousness, headache, dizziness, restlessness
Note: Side effects of isoprenaline usually disappear quickly and do not require discontinuation of treatment
ADDITIONAL REFERENCES:
None