Adenosine

Adenosine

Adenosine is an injectable antiarrhythmic indicated for acutetreatment of PSVT.

Pharmacokinetics

After I.V. administration, adenosine is probably distributed rapidly throughout the body. It’s metabolized inside RBCs as well as in vascular endothelial cells.

Pharmacodynamics

Adenosine depresses the pacemaker activity of the SA node, re-ducing the heart rate and the ability of the AV node to conduct im-pulses from the atria to the ventricles.

Pharmacotherapeutics

Adenosine is especially effective against reentry tachycardias (when an impulse depolarizes an area of heart muscle, then re-turns and repolarizes it) that involve the AV node.

No slouch

Adenosine also effectively resolves PSVT in 90% of cases. It’s typi-cally used to treat arrhythmias associated with accessory bypass tracts, as in Wolff-Parkinson-White syndrome (brief periods of rapid heart rate in which the rhythm originates above the ventri-cle).

Drug interactions

·                 Methylxanthines antagonize the effects of adenosine, so larger doses of adenosine may be necessary.

·                 Dipyridamole and carbamazepine potentiate the effects of adenosine, so smaller doses of adenosine may be necessary.

·                 When adenosine is administered with carbamazepine, there’s an increased risk of heart block. (See Adverse reactions to adeno-sine.)