How is 1 milligram (mg) of adrenaline (epinephrine) in 1 milliliter (ml) of solution equivalent to a 1:1000 concentration?

Understanding Adrenaline Concentration: 1 mg/mL = 1:1000

The 1:1000 concentration means there is 1 gram of adrenaline in 1000 mL of solution, which mathematically equals 1 mg in 1 mL. This is a standardized pharmaceutical notation that describes drug concentration as a ratio of mass to volume 1, 2.

Mathematical Explanation

The ratio notation works as follows:

• 1:1000 = 1 gram per 1000 mL 1
• Converting to smaller units: 1 gram = 1000 mg
• Therefore: 1000 mg per 1000 mL = 1 mg per 1 mL 2

This concentration is explicitly confirmed in FDA labeling, which states that Adrenalin® (epinephrine injection, USP) contains "1 mg/mL epinephrine" and is equivalent to "1:1000" 2.

Clinical Context and Concentration Comparison

Understanding this concentration is critical because adrenaline comes in two standard concentrations that serve different clinical purposes:

• 1:1000 (1 mg/mL): Used for intramuscular/subcutaneous administration in anaphylaxis, severe asthma, and croup 1
• 1:10,000 (0.1 mg/mL): Used for intravenous administration during cardiopulmonary resuscitation 1

Critical Safety Considerations

The most dangerous pitfall is selecting the wrong concentration for the intended route of administration, which can result in either a 10-fold overdose or underdose. 1

Dosing Conversion Formula

To prevent errors, the American Academy of Pediatrics provides this conversion:

• 0.01 mg/kg = 0.1 mL/kg of 1:10,000 solution 1
• 0.1 mg/kg = 0.1 mL/kg of 1:1000 solution 1

Route-Specific Guidelines

For anaphylaxis (intramuscular route):

• Adults: 0.3-0.5 mg = 0.3-0.5 mL of 1:1000 solution 1
• Children >12 years: 0.5 mg (0.5 mL of 1:1000) 1
• Children 6-12 years: 0.3 mg (0.3 mL of 1:1000) 1

For cardiac arrest (intravenous route):

• Use 1:10,000 concentration to avoid excessive vasoconstriction 1

Practical Verification

Before administering adrenaline, always verify:

• The concentration matches the intended route (IM/SC uses 1:1000; IV uses 1:10,000) 1
• The solution is clear and colorless (pink or brown discoloration indicates oxidation and the solution should be discarded) 2
• The calculation: dose in mg ÷ 1 mg/mL = volume in mL for 1:1000 concentration 1