1. 50-500 nanograms/kg/min (0.05-0.5 mcg/kg/min) by continuous IV infusion.

Indications

1. Low cardiac output and hypotension.
2. Persistent pulmonary hypertension of the newborn.

Contraindications and Precautions

1. Known hypersensitivity to isoprenaline.
2. Hypovolaemia.

Clinical Pharmacology

Isoprenaline hydrochloride is a synthetic sympathomimetic amine that is structurally related to adrenaline. The drug is a B₁ and B₂ adrenergic agonist with almost no activity on a receptors. Increases cardiac output by increasing heart rate, contractility and venous return. Lowers peripheral vascular resistance. Relaxes most smooth muscles, especially bronchial and gastrointestinal. Decreases pulmonary artery pressure and pulmonary artery resistance in experimental animals. Stimulates insulin secretion. Metabolised in the liver and other tissues by catechol-o-methyl transferase. Marked chronotropic and arrhythmogenic effects. May cause myocardial ischaemia or necrosis.

Possible Adverse Effects

1. Hypotension
2. Arrhythmias
3. Decreased perfusion to kidney, heart, brain.
4. Tremors, irritability.
5. Gastrointestinal disturbances (nausea, vomiting and diarrhoea).
6. Myocardial necrosis.

Special Considerations

1. Titrate infusion rate according to clinical response and/or side effects. May increase dose every 2-3 minutes until appropriate response obtained.
2. Hypovolaemia, metabolic acidosis should be corrected before infusion commences.
3. Simultaneous administration with adrenaline may lead to serious arrhythmias.