DESCRIPTION

Adenosine is an ultra short-acting antidysrhythmic agent.

FORMS AND USES

• Adenosine is used to interrupt tachydysrhythmics such as supraventricular tachycardias that are associated with conditions such as:
  • Thyrotoxicosis
  • Theophylline intoxication
  • Wolff-Parkinson-White syndrome
  • Lown-Ganong-Levine syndrome
• Adenosine for intravenous injection: 6 mg/2 ml and 12 mg/4 ml vials.
• Adenoscan for intravenous injection: 90 mg/30 ml vials.

MECHANISM OF ACTION

• Adenosine binds to adenosine-specific receptors that activate acetylcholine-sensitive potassium channels in the sinoatrial and atrioventricular (AV) nodes, as well as atrial myocardial tissue.
• Interference with the potassium current results in transient slowing of the sinus rate with slowing of the AV nodal conduction velocity and increasing AV nodal refractoriness.
• Adenosine has no direct effects on ventricular myocardium.
• The major advantage of adenosine is its ultra-short half-life (seconds). Thus, adverse events should resolve quickly.

DRUG AND DISEASE INTERACTIONS

• Dipyridamole and carbamazepine potentiate adenosine effects.
• Methylxanthines, such as theophylline and caffeine, are adenosine antagonists.

PREGNANCY AND LACTATION

US FDA Pregnancy Category C. Studies have shown that the drug exerts animal teratogenic or embryocidal effects, but there are no controlled studies in women, or no studies are available in either animals or women.

Section Outline:

• DESCRIPTION
• FORMS AND USES
• MECHANISM OF ACTION
• DRUG AND DISEASE INTERACTIONS
• PREGNANCY AND LACTATION

• Paroxysmal supraventricular tachycardia that is refractory to nonpharmacologic therapy.
• Toxic causes of supraventricular tachycardia may be refractory to adenosine therapy because the initiating stimulus usually persists beyond the half-life of adenosine.

CONTRAINDICATIONS

• Adenosine is contraindicated for second- or third-degree AV block unless an artificial pacemaker is present.
• It also should not be used for sick sinus syndrome due to the potential for prolonged asystole with loss of consciousness.

ADVERSE EFFECTS

• Adenosine may induce bronchospasm and therefore should be used with caution in patients with reactive airway disease.
• Hypotension may occur occasionally.
• Patients have reported:
  • chest tightness (1%)
  • lightheadedness (2%)
  • nausea (3%)
  • dyspnea (12%)
  • facial flushing (18%)

Section Outline:

• CONTRAINDICATIONS
• ADVERSE EFFECTS

• Adult: Initial dose should be 6 mg as a rapid intravenous bolus.
• Child: The initial dose in infants and children is 50 µg/kg.
• The patient must be closely monitored, and resuscitation equipment should be available during adenosine therapy.
• Due to its half-life of only 10 seconds, adenosine will be inactivated before reaching the heart if infused slowly via a peripheral intravenous route. Therefore, it should be pushed via rapid bolus through a central intravenous line.
• If the dysrhythmia does not respond within 1 to 2 minutes, a dose of 12 mg should be pushed via rapid intravenous bolus.
• The 12-mg dose may be repeated in 1 to 2 minutes. If the third dose of adenosine does not eliminate the dysrhythmia, then alternative therapies should be pursued and the diagnosis reconsidered.
• The second and third doses in infants and children should be 100 and 150 µg/kg, respectively.

• The clinician must push adenosine rapidly, thereby avoiding inactivation of the drug before it reaches the heart.
• It is important to identify paroxysmal supraventricular tachycardia correctly. Adenosine will be ineffective in converting other tachydysrhythmias, such as atrial fibrillation, atrial flutter, or ventricular tachycardia, into a sinus rhythm.
• No controlled studies exist regarding the safety and efficacy in pediatric patients.

Poisoning by agents primarily affecting the cardiovascular system.

RECOMMENDED READING

Faulds D, Chrisp P, Buckley MM-T. Adenosine: an evaluation of its use in cardiac diagnostic procedures and in the treatment of paroxysmal supraventricular tachycardia. Drugs 1991;41:596-624.

Till J, Shinebourne EA, Rigby ML, Clarke B, Ward DE, Rowland E. Efficacy and safety of adenosine in the treatment of supraventricular tachycardia in infants and children. Br Heart J 1989;62:204-211.

Author: Gerald F. O'Malley

Reviewer: Richard C. Dart