Adrenaline Concentration Calculation — MFDS Part 1 MCQ

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HardPharmacologyAdrenaline Concentration CalculationMFDS Part 1

A dental local-anaesthetic cartridge contains 2.2 mL of lidocaine 2% solution with adrenaline at a ratio strength of 1:80,000. Which option correctly states both the concentration of adrenaline and the total amount of adrenaline in one full cartridge?

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Correct answer: A — 12.5 micrograms/mL; 27.5 micrograms per cartridge

Option A is correct. A ratio strength of 1:80,000 denotes 1 g of adrenaline in 80,000 mL. Converting 1 g to 1,000,000 micrograms gives 1,000,000 ÷ 80,000 = 12.5 micrograms/mL; a full 2.2 mL cartridge therefore contains 12.5 × 2.2 = 27.5 micrograms. This matches the UK dm+d listing of the standard lidocaine 2% with adrenaline 1:80,000 dental product as 12.5 micrograms/mL. Option E mistakes the ratio denominator for a per-mL amount. Option C wrongly assumes 1 gram in 80,000 mL yields 1 microgram/mL by misplacing the unit conversion. Option B corresponds to 1:10,000, the resuscitation dilution, not the dental cartridge strength. Option D (8 micrograms/mL) results from inverting the calculation (80,000 ÷ 1,000,000 × 100) and would correspond to 1:125,000. Knowing the microgram dose per cartridge is clinically important when calculating maximum adrenaline doses in cardiovascularly compromised patients.

Reference: NHS Business Services Authority, dm+d browser — Lignospan Special 20mg/ml / 12.5micrograms/ml solution for injection cartridges (lidocaine 2% with adrenaline 1:80,000), https://dmd-browser.nhsbsa.nhs.uk/amp/view/142164