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Cardiac drugs aren’t interchangeable — and neither are their administration speeds.

The difference between pushing in 2 seconds versus 2 minutes can mean:

Rhythm conversion

Severe hypotension

Bronchospasm

Or cardiac arrest

Today’s framework:

Push Fast

Push Slow

Never Push

Assess Before Push

Use: Stable narrow-complex SVT
Mechanism: Temporarily blocks the AV node
Half-life: Less than 10 seconds

If you don’t push it rapidly (1–2 seconds with immediate flush), it metabolizes before it reaches the heart.

Expect brief asystole (6–7 seconds)

Warn the patient about chest pressure and “impending doom”

Use lower doses in heart transplant patients

Not effective for ventricular rhythms

Clinical Judgment: If you're unsure whether it’s SVT or something else, adenosine can help reveal the underlying rhythm.

This is a high-alert medication.

Rapid potassium destroys the resting membrane gradient.
The heart depolarizes — and cannot repolarize.

Result: Immediate cardiac arrest.

Never IV push

Peripheral max: 10 per hour

Central max: 20 per hour (ICU with monitoring)

Always mix thoroughly (invert bag at least 10 times)

Muscle weakness

Urine output decreasing

Respiratory distress

Decreased contractility

ECG changes (peaked T-waves)

Reflex changes

This is a system-safety drug. Treat it with respect.

Narrow therapeutic window.

Digoxin and potassium compete at the same cellular pump.
Low potassium increases toxicity risk.

Apical pulse for a full 60 seconds

Hold if under 60

Review potassium level

Monitor for visual changes (yellow halos)

Watch for nausea, confusion, or bizarre symptoms (like smelling flowers)

Antidote: Digoxin immune fab
Best strategy: Prevention through assessment

Use: Rate control

Rapid administration can cause:

Severe hypotension

Profound bradycardia

Loss of compensatory sympathetic tone

Give over 1–2 minutes

Monitor heart rhythm and blood pressure continuously

Use caution in asthma/COPD (beta receptor selectivity can spill over)

Beta blockers can mask hypoglycemia symptoms in diabetics

Never stop abruptly — risk of rebound hypertension and ischemia

Push Fast: Adenosine

Never Push: Potassium chloride

Assess Before Push: Digoxin

Push Slow: Metoprolol

Speed is physiology.
Administration is pharmacology in motion.
Clinical judgment is what makes you safe.

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