What volume of bacteriostatic water should be added to a 60mg powder vial of Retatrutide to achieve a concentration suitable for a 2mg weekly dose using a U-100 syringe?

Reconstitution of Retatrutide for Weekly 2mg Dosing

For a 60mg vial of Retatrutide powder, add 3mL of bacteriostatic water to achieve a concentration of 20mg/mL, allowing you to draw up 0.1mL (10 units on a U-100 insulin syringe) for a 2mg weekly dose.

Calculation Logic

When reconstituting injectable medications, the key is to create a concentration that allows for accurate and convenient dosing. Here's the step-by-step approach:

1. Determine desired concentration:

   • You need to administer 2mg weekly
   • Using a U-100 insulin syringe (100 units per 1mL)
   • Ideal volume for injection: small volume (0.1-0.2mL) for subcutaneous administration

2. Calculate appropriate concentration:

   • With 60mg of powder, adding 3mL of bacteriostatic water creates a 20mg/mL solution
   • Formula: Concentration = Total drug amount ÷ Total volume
   • 60mg ÷ 3mL = 20mg/mL

3. Calculate injection volume:

   • For a 2mg dose: 2mg ÷ 20mg/mL = 0.1mL
   • On a U-100 insulin syringe, this equals 10 units (easy to measure)

Preparation Technique

When reconstituting the medication:

1. Use sterile technique throughout the preparation process
2. Sanitize the vial stopper with 70% isopropanol before needle insertion
3. Slowly inject the bacteriostatic water along the vial wall to avoid foaming
4. Gently swirl (don't shake) until completely dissolved
5. Inspect for clarity and absence of particulate matter
6. Store according to manufacturer recommendations (typically refrigerated)

Important Considerations

• Bacteriostatic water contains a preservative (typically 0.9% benzyl alcohol) that inhibits bacterial growth, making the reconstituted solution stable for multiple uses
• Using the 20mg/mL concentration allows for precise dosing with minimal injection volume
• Higher concentrations would make accurate measurement difficult on a U-100 syringe
• Lower concentrations would require larger injection volumes, potentially causing more discomfort

This reconstitution approach balances the need for accurate dosing with practical considerations for subcutaneous administration of a weekly medication.