What is the ratio of adrenaline solution in 1mg/mL of injection?

Appeared in: Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Explanation

A concentration of 1 mg/mL indicates that 1 milligram of the drug is dissolved in 1 milliliter of solvent.
To express this as a weight-to-weight ratio, the units must be consistent.
The solvent in injections is typically aqueous, meaning 1 mL of the solvent has a mass of approximately 1 gram.
Since 1 gram is equal to 1000 milligrams, the concentration is effectively 1 mg of drug in 1000 mg of solvent.
This simplifies to a final ratio of 1:1000.

Option A: A 1:1 ratio would mean 1 mg of adrenaline in 1 mg of solvent, or 1 gram per mL. This represents a 100% concentration, which is not the standard preparation and would be extremely potent.
Option B: A 1:10 ratio would mean 1 mg of adrenaline in 10 mg of solvent. This is equivalent to a concentration of 100 mg/mL, which is 100 times more concentrated than the standard 1 mg/mL solution.
Option C: A 1:100 ratio would mean 1 mg of adrenaline in 100 mg of solvent. This is equivalent to a concentration of 10 mg/mL, which is 10 times more concentrated than the standard 1 mg/mL solution.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Drug Concentration and Ratio Calculation as background academic context rather than a clinical decision trigger.
Understanding adrenaline concentrations is critical for patient safety. Administering the wrong concentration can be fatal.
The 1:1000 solution is more concentrated and is typically used for intramuscular (IM) or subcutaneous (SC) injection for anaphylaxis.
The 1:10,000 solution is more dilute and is used for intravenous (IV) or intraosseous (IO) injection, primarily during cardiac arrest.

How to Approach the Question

First, identify the given concentration from the question stem: 1 mg/mL.
Recognize that a ratio compares parts of the same unit (e.g., mass to mass or volume to volume).
Convert the volume of the solvent (1 mL) to its approximate mass. For water-based solutions, 1 mL has a mass of approximately 1 gram.
Convert all units to be the same. Change 1 gram to 1000 milligrams.
Now, compare the mass of the drug (1 mg) to the mass of the solvent (1000 mg).
This comparison gives the final ratio of 1:1000.

Concept Tested & Keywords

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E6 Pharmacology Nurses Shanbhag 3e pp. 57-59, 83-85

E6 Pharmacology Nursing Lilley 11e Part 1 p. 318-320

Practise the full Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)

Attempt every question from this paper in a timed mock, then review the full solution for each one.