ISOPRENALINE

“ISOPROTERENOL; ISUPREL”

1) Therapeutic drug action & mechanism(pharmacology)

• Acts almost exclusively on b-adrenergic receptors

• Causes i) Inotrope [b₁-receptors]

ii) Chronotrope [b₁-receptors]

iii) Vasodilator [b₂-receptors]—potent effect

iv) Bronchodilation [b₂-receptors]

• Reduces SVR & PVR via vasodilation & pulmonic vasodilation

2) Indications

• Ventricular dysfunction especially RV(combination of pulmonary dilation & inotropic support)

• Bronchoconstriction

• Bradycardias

• Pulmonary hypertension (inotrope of choice if require inotropic support in such a patient)

3) Effects on organs—side effects

• Also increases venous return to heart

4) Toxic effects/ precautions with administration

• Tachycardias, dysrythmias (due to b₁ effects)

• Reduced coronary diastolic perfusion pressures (due to b₂ effects)

• Increased MVO₂ (due to tachycardia) plus reduced myocardial O₂ supply (due to reduced coronary diastolic perfusion pressures) may extend ischaemic areas

5) Contraindications

• Idiopathic hypertrophic subaortic stenosis

• Tetralogy of Fallot with RV outflow tract obstruction (as may constrict pulmonary vasculature exacerbating preexisting pulmonary hypertension or right ventricular dysfunction

7) Loading dose, maintenance dose, frequency & method of administration

• 0.2 mg/ml; 1mg/5ml ampules

• Dilute in 500 ml D5W

• Run at 0.5 - 5 mg/min

8) Drug’s metabolism—Drug’s excretion—Half life (pharmacokinetics)

• 60 - 90 min duration of effect

9) Important drug interactions

• Should not be administered concommitantll with adrenaline as will dangerously exacerbate adrenergic effects resulting in arrythmias

• Risk of arrythmias with volatile anaesthetics