Indications: rapid reversion to sinus rhythm of paroxysmal supraventricular tachycardia, including those associated with accessory pathways (e.g. Wolff- Parkinson-While syndrome); aid to diagnosis of broad or narrow complex supraventricular tachycardias.

Cautions: atrial fibrillation or flutter with accessory pathway (conduction down anomalous pathway may increase); heart transplant.

Interactions: Myocardial depression is enhanced by local anaesthetics, beta blockers, antiarrhythmic drugs, dipyridamole.

Contra-indications: second– or third- degree AV block and sick sinus syndrome (unless pacemaker fitted); asthma.

Side Effects: transient facial flush, chest pain, dyspnea, bronchospasm, choking sensation, nausea, light- headedness; severe bradycardia; ECG may show transient rhythm disturbances.

Dose: by rapid intravenous injection into central or large peripheral vein, 3 mg over 2 seconds with cardiac monitoring; if necessary followed by 6 mg after 1-2 minutes, and then by 12 mg after a further 1-2 minutes; increments should not be given if high level AV block develops.

Note: 3 mg dose ineffective in a number of patients, therefore higher initial dose sometimes used but patients with heart transplant are very sensitive to effects of adenosine, and should not receive higher initial dose.