Adenosine

Chemical

An endogenous nucleotide present in all metabolising cells

Made of a purine base (adenine) & a sugar (ribose)

Use

  1. SVTs
  2. Differentiate flutter & SVT

Presentation

Clear, colourless solution 3mg/mL

Dose

(IV) 6mg → 12mg at q2mins

Give as centrally as possible with rapid flush

Route

IV

Onset

Rapid, needs to be flushed

OFFSET:

  • Rapid t ½ 10 secs

Deaminated to INOSINE + AMP in plasma or taken up by RBC

MoA (mechanism)

Agonist of adenosine receptors

Receptor

A1

SA Node

Atrium

 

Messenger

  1. Gi

↓

Inhibits AC

↓

cAMP

↓

↓Ca2+

  1. Stimulates adenosine sensitive K+ channels

↓

↑K+ conductance

↓

Hyperpolarises supraventricular myocytes

Effect

↓Ca2+ influx = negative INOTROPY

Inhibition of AV conduction = negative DROMOTROPY

Receptor

A2

Smooth muscle of arteries & coronary arteries!

Messenger

  1. G5

↓

Activates AC

↓

↑cAMP

↓

Inhibits M1CK

↓

Relaxes smooth m.

Effect

Vasodilation

↑coronary BF

ECG effects: ↓HR

PD

CVS

  • AV block à slows ventricular response

→ Terminates SVT

→ Reveals atrial arrythmia

RESP

  • ↑MV
  • A2 receptors of carotid body stimulated

CNS – ↑CBF

Metabolic – stimulates glycolysis

PK

A

Inactivated orally

D

Quick 10s t½

Needs to be followed by rapid IV bolus

M

Deaminated to INOSINE + AMP in plasma or taken up by RBC

E

Taken up by RBC

t ½ 10 secs

Adverse Effects

  • Transient flushing
  • Dyspnoea, bronchospasm
  • Chest discomfort
  • Profound bradycardia requiring pacing