How much sterile water is needed to reconstitute a 12mg powder vial of retatrutide for a 4mg subcutaneous (SQ) injection?

Reconstitution of Retatrutide 12mg Powder Vial

Direct Answer

To achieve a 4mg dose from a 12mg vial of retatrutide, reconstitute the powder with 3mL of sterile water, which will yield a concentration of 4mg/mL, allowing you to draw up 1mL for each 4mg weekly injection.

Calculation Method

The reconstitution volume is determined using basic pharmaceutical mathematics to achieve a practical concentration:

• Target concentration: 4mg/mL allows for easy measurement and administration 1
• Calculation: 12mg powder ÷ 4mg/mL = 3mL of sterile water needed 1
• Resulting doses: This provides exactly 3 doses of 4mg (1mL each) from the single 12mg vial 2, 3

Step-by-Step Reconstitution Protocol

Preparation requirements:

• Maintain strict sterile technique throughout the entire process to prevent contamination 1
• Use appropriate sterile syringes for measuring and transferring the sterile water 1
• Ensure all materials are at room temperature before beginning 1

Reconstitution procedure:

• Draw up exactly 3mL of sterile water for injection using a sterile syringe 1
• Inject the 3mL slowly into the 12mg powder vial, directing the stream against the vial wall rather than directly onto the powder 1
• Gently swirl (do not shake vigorously) until the powder is completely dissolved 1
• Inspect the reconstituted solution visually for particulate matter and discoloration before use - the solution should be clear 1

Storage and Stability

Critical storage guidelines:

• Label the reconstituted vial immediately with medication name, concentration (4mg/mL), date and time of reconstitution, and expiration 1
• Store at 4°C (refrigerated) to extend stability compared to room temperature 1
• Discard after 24 hours if manufacturer-specific stability data is not available 1
• Never freeze the reconstituted solution 1

Administration Details

For each weekly 4mg dose:

• Draw up exactly 1mL from the reconstituted vial (1mL = 4mg at 4mg/mL concentration) 2, 3
• Administer subcutaneously as studied in clinical trials 2, 3
• The clinical trials used weekly subcutaneous administration with dose escalation protocols starting at 2mg for higher doses 3

Critical Safety Warnings

Important considerations:

• Reconstituting without manufacturer-specific instructions poses significant patient safety risks including incorrect concentration leading to dosing errors 1
• Incompatibility with certain diluents can cause drug degradation - only use sterile water for injection unless otherwise specified 1
• This calculation assumes the powder volume is negligible; actual final volume may be slightly greater than 3mL 1
• In clinical trials, retatrutide demonstrated dose-dependent gastrointestinal adverse events (nausea, diarrhea, vomiting) that were mostly mild to moderate 2, 3
• Dose-dependent increases in heart rate were observed in trials, peaking at 24 weeks 2

Alternative Concentration Option

If you prefer smaller injection volumes or different dosing flexibility:

• 6mL reconstitution: Using 6mL sterile water yields 2mg/mL concentration, requiring 2mL per 4mg dose 1
• This provides the same three 4mg doses but with larger injection volumes 1