Adenosine is a vasodilating agent, which acts on the vascular smooth muscle surface and leads to vasodilation and a considerable increased vascular flow.

NB: This article aims to give a summarized description of adenosine. For detailed and exact information please refer to the information and direction for use or package insert from the pharmaceutical company.

Usage

It is commonly used for diagnostic purposes in cardiac stress testing and will accentuate the difference between the normal coronary arteries, which dilate under adenosine administration, and coronary stenoses, which remain fixed and cannot dilate any further ^1-3.

It has been also used for diagnostic purposes and treatment in supraventricular tachycardia ³.

Effects

Adenosine binds non-selectively to A1, A2A, A2B and A3 receptors of which activation of A2A receptors lead to coronary vasodilation, which is required for the cardiac stress test ^1,3.

Activation of A1, A2B and A3 receptors can lead to bronchospasm and atrioventricular block ¹.

Adenosine has a half-life of 10-30 seconds.

Dosage

The usual dosage used on cardiac stress tests is the following ^1,2:

• infusion of 140 µg/kg for 2-4 minutes

if there is no increase in heart rate by 10 beats per minute (bpm) or drop in blood pressure by ≥10 mmHg after 2-3 min of infusion an increase to 210 µg/kg might be considered subject to local and institutional norms ².

Contraindications

Contraindications of adenosine include ^1,2:

• 2nd or 3rd-degree atrioventricular block

• sinus bradycardia (<40-45 bpm)

• systolic blood pressure ≤90 mmHg

• severe arterial hypertension (e.g. ≥220/120 mmHg)

• acute myocardial infarction

• known hypersensitivity to adenosine

• active bronchoconstriction, asthma or bronchospastic disease requiring regular inhaler use

• severe aortic stenosis or carotid stenosis

• cardiac shunt

Interacting agents

• xanthines such as aminophylline, theophylline, and caffeine act as competitive antagonists

• dipyridamole potentiates its action

Antidote

The treatment of adenosine toxicity is by intravenous aminophylline: suggested dose 125 mg in 50 mL normal saline by IV infusion for 5–6 min.