adenosine
Adenocard

Available forms
Available by prescription only
Injection: 3 mg/ml

Indications and dosages
 Conversion of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm. Adults: 6 mg I.V. by rapid bolus injection (over 1 to 2 seconds). If PSVT isn’t eliminated in 1 to 2 minutes, give 12 mg by rapid I.V. push. Repeat 12-mg dose if necessary. Single doses over 12 mg aren’t recommended.

Pharmacodynamics
Antiarrhythmic action: Adenosine is a naturally occurring nucleoside. In the heart, it acts on the AV node to slow conduction and inhibit reentry pathways. Adenosine is also useful for the treatment of PSVT linked to accessory bypass tracts (Wolff-Parkinson-White syndrome).

Pharmacokinetics
Absorption: Administered I.V.
Distribution: Rapidly taken up by erythrocytes and vascular endothelial cells.
Metabolism: Metabolized within tissues to inosine and adenosine monophosphate.
Excretion: Unknown; circulating plasma half-life is less than 10 seconds.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug and in those with second- or third-degree heart block or sick sinus syndrome, unless an artificial pacemaker is present, because adenosine decreases conduction through the AV node and may produce first-, second-, or third-degree heart block. These effects are usually transient; however, patients for whom significant heart block develops after a dose of adenosine shouldn’t receive additional doses.
  Don’t use in atrial fibrillation or atrial flutter. Use cautiously in patients with asthma because bronchoconstriction may occur.

Interactions
Drug-drug. Carbamazepine: Higher degrees of heart block occur in patients receiving concurrent therapy. Avoid use together.
Dipyridamole: May potentiate adenosine effects. Smaller adenosine doses may be needed.
Methylxanthines: Antagonize effects of adenosine. Patients receiving theophylline may need higher doses or may not respond to adenosine therapy.
Drug-herb. Guarana: May decrease response to adenosine. Monitor patient closely.
Drug-food. Caffeine: May antagonize effects of adenosine. Patient may need higher doses or may not respond to adenosine therapy.

Adverse reactions
CNS: apprehension, burning sensation, dizziness, headache, heaviness in arms, light-headedness, numbness, tingling in arms.
CV: chest pain, facial flushing, hypotension, palpitations.
EENT: blurred vision, throat tightness.
GI: metallic taste, nausea.
GU: groin pressure.
Musculoskeletal: back pain, neck pain.
Respiratory: chest pressure, dyspnea, shortness of breath, hyperventilation.
Skin: diaphoresis.

Effects on lab test results
None reported.

Overdose and treatment
Because the half-life of adenosine is less than 10 seconds, the adverse effects of overdose usually dissipate rapidly and are self-limiting.
 Treat lingering adverse effects symptomatically.

Special considerations
• Check solution for crystals, which may form if solution is cold. If crystals are visible, gently warm solution to room temperature. Don’t use solutions that aren’t clear.
• Use Adenocard cautiously in patients with previous history of ventricular fibrillation or those taking digoxin and verapamil.
 ALERT Rapid I.V. injection is needed for drug action. Administer directly into a vein if possible; if an I.V. line is used, use the most proximal port and follow with a rapid saline solution flush to ensure that drug reaches the systemic circulation rapidly.
• Monitor ECG rhythm during administration; drug may cause short-lasting first-, second-, or third-degree heart block or asystole.
• Discard unused drug because it contains no preservatives.
 ALERT Don’t confuse adenosine phosphate with adenosine (Adenocard).
Pediatric patients
• There have been no controlled studies.

Patient education
• Warn patient of adverse reactions and advise patient to call if they occur.
• Tell patient to report discomfort at I.V. site.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use