Loading dose
Formal Definition
An initial higher-than-maintenance dose of a medication given to rapidly achieve therapeutic drug levels, reaching steady-state concentration immediately rather than waiting through multiple half-lives of standard dosing.
How It's Used on the Ward
"Give a load" or "load with amiodarone" — a front-loaded dose before the maintenance regimen.
Example
""New atrial fibrillation with RVR in the ICU: amiodarone 150mg IV bolus over 10 minutes (loading dose), then drip at 1mg/min for 6 hours, then 0.5mg/min for 18 hours (maintenance). Rate came down to 80s within 20 minutes.""
Clinical Context
Loading dose rationale: without it, drugs with long half-lives take 4–5 half-lives to reach steady state. Amiodarone t½ is weeks — a maintenance dose alone would never achieve therapeutic levels acutely. Other common loads: IV levothyroxine in myxedema coma, phenytoin for seizure, vancomycin (weight-based load), digoxin. Loading doses carry higher risk of toxicity — monitor closely after administration.
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