Intropin

Action

Causes norepinephrine release (mainly on dopaminergic receptors), leading to vasodilation of renal and mesenteric arteries. Also exerts inotropic effects on heart, which increases the heart rate, blood flow, myocardial contractility, and stroke volume.

Availability

Injection for dilution: 40 mg/ml, 80 mg/ml, 160 mg/ml

Premixed injection: 0.8 mg/ml, 1.6 mg/ml, 3.2 mg/ml in 250 ml and 500 ml of dextrose 5% in water

Indications and dosages

➣ Shock; hemodynamic imbalance; hypotension; heart failure

Adults and children: 2 to 5 mcg/kg/minute by I.V. infusion. Titrate dosage to desired response; may increase infusion by 1 to 4 mcg/kg/minute at 10- to 30-minute intervals. Maximum dosage is 50 mcg/kg/minute.

Contraindications

• Hypersensitivity to drug or bisulfites

• Tachyarrhythmias, ventricular fibrillation

• Pheochromocytoma

Precautions

Use cautiously in:

• hypovolemia, myocardial infarction, occlusive vascular disease, diabetic endarteritis, atrial embolism

• concurrent MAO inhibitor use

• pregnant or breastfeeding patients

• children.

Administration

• Give I.V. infusion using metered pump or other device that controls flow.

• Add 200 to 400 mg of dopamine to 250 to 500 ml of normal saline solution, 5% dextrose injection, 5% dextrose and half-normal saline solution, or 5% dextrose in lactated Ringer's solution.

• Infuse into large (preferably central) vein to minimize extravasation.

☞ Don't give concurrently with MAO inhibitors. Reduce dosage if patient has received MAO inhibitor recently.

Adverse reactions

CNS: headache

CV: palpitations, hypotension, angina, ECG changes, tachycardia, vasoconstriction, arrhythmias

EENT: mydriasis

GI: nausea, vomiting

Metabolic: azotemia, hyperglycemia

Respiratory: dyspnea, asthma attacks

Skin: piloerection

Other: irritation at injection site, gangrene of extremities (with high doses for prolonged periods or in occlusive vascular disease)

Interactions

Drug-drug. Alpha- or beta-adrenergic blockers: antagonism of dopamine effects

Ergot alkaloids: extreme blood pressure increase

Guanethidine: decreased cardiostimulatory effects

Inhalation anesthetics: increased risk of hypertension, arrhythmias

MAO inhibitors: hypertensive crisis

Oxytocics: severe, persistent hypotension

Phenytoin: seizures, severe hypotension, bradycardia

Tricyclic antidepressants: decreased pressor response

Drug-diagnostic tests. Glucose, nitrogenous compounds, urine catecholamines: increased levels

Patient monitoring

• Monitor blood pressure, pulse, urinary output, and pulmonary artery wedge pressure during infusion.

☞ Inspect I.V. site regularly for irritation. Avoid extravasation.

☞ Monitor color and temperature of extremities.

☞ Never stop infusion abruptly, because this may cause severe hypotension. Instead, taper gradually.

Patient teaching

• Explain the need for close observation during infusion.

• Instruct patient to report adverse reactions and I.V. site discomfort.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.