What volume of sterile water is needed to reconstitute 12mg of retatrutide for an 8mg subcut dose?

Reconstitution Calculation for Retatrutide 8mg Dose

To achieve an 8mg dose from a 12mg vial, reconstitute with 6.67 mL of sterile water, which will yield a concentration of 1.8 mg/mL, allowing you to draw up 4.44 mL for the 8mg dose.

Mathematical Calculation

The reconstitution volume is determined by working backwards from your desired dose:

• Target dose: 8 mg subcutaneously
• Available powder: 12 mg retatrutide
• Desired concentration: You need a concentration that makes dosing practical

Using the principle that concentration = amount/volume:

• If you want to draw up approximately 4-5 mL (a reasonable volume for subcutaneous injection), you need a concentration around 1.8 mg/mL 1
• To achieve 1.8 mg/mL from 12 mg powder: 12 mg ÷ 1.8 mg/mL = 6.67 mL of sterile water
• This yields: 8 mg ÷ 1.8 mg/mL = 4.44 mL to withdraw for your dose

Alternative Simplified Approach

For easier calculation, you could reconstitute with 6 mL of sterile water:

• This creates a 2 mg/mL concentration (12 mg ÷ 6 mL)
• Draw up exactly 4 mL for your 8 mg dose (8 mg ÷ 2 mg/mL = 4 mL)
• This is more straightforward for clinical practice 2

Critical Safety Considerations

Sterile technique is mandatory throughout the reconstitution process 1:

• Sanitize vial stoppers with 70% isopropanol before needle puncture 2
• Use only sterile water for injection (preservative-free) 2
• Avoid direct contact contamination of needles and syringes 2

Stability and storage limitations 3:

• Reconstituted peptide medications have limited stability
• Use immediately after reconstitution when possible
• If storage is necessary, refrigerate at 4°C and use within manufacturer-specified timeframe
• Do not store unless stability data supports it 2, 4

Common Pitfalls to Avoid

• Do not use the full 10 mL vial of sterile water - this would create an unnecessarily dilute solution (1.2 mg/mL) requiring you to draw up 6.67 mL, which is impractical for subcutaneous injection 1
• Visual inspection is required - examine the reconstituted solution for particulate matter or discoloration before administration 2, 1
• Verify calculations with a colleague - double-check both the reconstitution volume and the withdrawal volume to prevent dosing errors 2, 1
• Label the vial immediately after reconstitution with patient name, concentration, date/time of reconstitution, and beyond-use date 2