Adenosine

Adenosine

Indication

• For conversion of paroxysmal supraventricular tachycardia (PSVT), including that associated with accessory bypass tracts (Wolff-Parkinson-White Syndrome), to normal sinus rhythm

Pharmacology

• An endogenously occurring nucleoside
• Profoundly blocks AV node, therefore allows examination of rapid atrial rhythms and can interrupt re-entry pathways through the A-V node
• Adenosine is believed to produce its effects via an interaction with specific cell surface receptors which are coupled to a regulatory G protein
• Adenosine also appears to increase potassium conductance, depress calcium - mediated slow channel conduction and possibly antagonize catecholamine mediated effects
• Adenosine is rapidly metabolized by adenosine deaminase in whole blood and by endothelial cells to inosine; it's in vitro half life, in human blood, is less than 10 seconds; therefore, any physiological effects (E.G. first, second or third degree heart block) are usually self-limiting and short lived

Side Effects

• The most common side effects, reported in clinical trials in adults, include flushing (18%), shortness of breath/dyspnea (12%), and chest pressure (7%)
• Other side effects which occurred in approximately 1% of patients include sweating, palpitations, hypotension, dizziness numbness and hyperventilation

Precautions

• Adenosine is contraindicated in second or third degree A-V block and in sick sinus syndrome
• Adenosine may cause first, second or third degree heart block; because of adenosine's very short half life, these effects are usually self-limiting and short-lived
• Various arrhythmias (E.G. sinus bradycardia, sinus tachycardia, atrial or ventricular premature contractions) may occur at the time of conversion; these generally last only a few seconds and do not require intervention
• Methylxanthines (eg. theophylline, caffeine) antagonize the actions of adenosine; larger doses of adenosine may be required or it may not be effective

Dose

• 50 mcg/kg rapid IV push (preferably through the umbilical vein) by MD only
  Flush immediately with 0.9% NaCl
  Increase dose in 50 mcg/kg increments every 2 minutes until sinus rhythm is established. Usual maximum dose is 250 mcg/kg
• Adenosine has also been administered as a continuous IV infusion in a pediatric patient; the initial infusion rate was 0.05 mcg/kg/min; this was increased to a maximum rate of 0.3 mcg/kg/min
• Adenosine may be diluted to 1 mg/mL as follows:
  • 0.33 mL of adenosine solution (3 mg/mL) plus 0.67 mL of 0.9% NaCl = adenosine 1 mg/mL
• This diluted product is physically stable for at least 24 hours. 
• Do not refrigerate
  • Note that there is no preservative present
• Hepatic and/or renal failure should have no effect on the dose or activity of adenosine, since neither organ is involved in its metabolism

Supplied

• 3 mg/mL, 2 mL vial