How can I dilute a 60 mg/2 mL (30 mg/mL) solution to obtain 0.5 % (5 mg/mL) and 1 % (10 mg/mL) concentrations?

Dilution Calculation for 60mg/2mL Solution

To prepare a 0.5% concentration (5 mg/mL) from your 60mg/2mL (30 mg/mL) stock solution, dilute 1 part of the stock solution with 5 parts of diluent (1:6 ratio total volume). To prepare a 1% concentration (10 mg/mL), dilute 1 part of the stock solution with 2 parts of diluent (1:3 ratio total volume).

Understanding Your Starting Concentration

Your preparation is 60 mg/2 mL, which equals 30 mg/mL (or 3% concentration when expressed as percentage).

Dilution Formulas and Calculations

For 0.5% Concentration (5 mg/mL):

• Dilution factor needed: 30 mg/mL ÷ 5 mg/mL = 6
• Practical mixing: Take 1 mL of your stock solution and add 5 mL of sterile water or normal saline to achieve a final volume of 6 mL
• Verification: 60 mg ÷ 12 mL = 5 mg/mL ✓

For 1% Concentration (10 mg/mL):

• Dilution factor needed: 30 mg/mL ÷ 10 mg/mL = 3
• Practical mixing: Take 1 mL of your stock solution and add 2 mL of sterile water or normal saline to achieve a final volume of 3 mL
• Verification: 60 mg ÷ 6 mL = 10 mg/mL ✓

Step-by-Step Preparation Method

For 0.5% Solution:

1. Draw up 1 mL of the 60mg/2mL stock solution
2. Add to a sterile container
3. Add 5 mL of appropriate diluent (sterile water or 0.9% sodium chloride)
4. Mix thoroughly
5. Final concentration: 5 mg/mL (0.5%)

For 1% Solution:

1. Draw up 1 mL of the 60mg/2mL stock solution
2. Add to a sterile container
3. Add 2 mL of appropriate diluent (sterile water or 0.9% sodium chloride)
4. Mix thoroughly
5. Final concentration: 10 mg/mL (1%)

Critical Safety Considerations

Always label diluted solutions clearly with the final concentration, date of preparation, and expiration. Diluted solutions typically have shorter stability than commercial preparations 1.

Use appropriate diluent: For most medications, sterile water or 0.9% sodium chloride (normal saline) is appropriate. The choice depends on the specific medication being diluted.

Storage considerations: Store diluted solutions in light-protected containers at room temperature unless otherwise specified. Most extemporaneously prepared dilutions should be used within 24-48 hours unless stability data supports longer storage 1.

Common Pitfall to Avoid

The most critical error is confusing percentage concentration with ratio concentration (e.g., 1:1000 vs 1%). A 1% solution equals 10 mg/mL, while a 1:1000 solution equals 1 mg/mL 2. Always verify your final concentration in mg/mL to prevent dosing errors.