💊 Adenosine

Adenosine is one of those drugs that looks simple on paper but trips students up on the NREMT because of strict patient selection criteria. It's the drug of choice for stable narrow-complex re-entrant SVT when vagal maneuvers fail. Here's the key: the patient must be STABLE. If they're hypotensive, have chest pain, altered mental status, or pulmonary edema — you don't reach for adenosine, you reach for the sync button.

The mechanism is fascinating: adenosine temporarily blocks AV nodal conduction, effectively resetting the re-entrant circuit that's causing SVT. Because its half-life is under 10 seconds, you MUST give it as a rapid IV push followed immediately by a 20 mL saline flush — ideally through a proximal vein (antecubital) with the arm elevated. The "fast flush" technique is something the NREMT may ask about directly.

Side effects are predictable and transient: chest pressure, facial flushing, dyspnea, and a feeling of impending doom that lasts maybe 15-20 seconds. Warn your patient before you push — otherwise they'll think they're dying. Adenosine can also cause brief asystole (a few seconds) which is actually the therapeutic goal — the SA node usually kicks back in with a normal rhythm.

NREMT study tip: memorize the contraindications. Atrial fibrillation/flutter, atrial tachycardia, and ventricular tachycardia will NOT convert with adenosine. The test loves giving you a wide-complex tachycardia to see if you recognize it's VT (sync cardiovert) vs SVT with aberrancy (adenosine). Also remember: methylxanthines (caffeine, theophylline) block adenosine's effect — you may need higher doses in heavy coffee drinkers.

💉 Dosage & Administration

Adult: 6 mg IV rapid push, then 12 mg if no conversion after 1-2 minutes

Pediatric: 0.1 mg/kg (max 6 mg), then 0.2 mg/kg (max 12 mg)

Route: IV rapid push followed by 20 mL saline flush

Onset: 10-20 seconds

Duration: 10-20 seconds (half-life < 10 seconds)

Notes: Must give as RAPID IV push with immediate saline flush — drug is cleared from circulation in seconds. Warn patient they'll feel chest pressure, flushing, and a sense of doom.