How to Mix 5-FU 50 mg/mL with Triamcinolone Acetonide (TA) 40 mg/mL in a 9:1 Ratio
To achieve a 9:1 volume ratio of 5-FU to TA, draw 0.9 mL of 5-fluorouracil (50 mg/mL) and 0.1 mL of triamcinolone acetonide (40 mg/mL) into the same syringe for a total volume of 1.0 mL.
Practical Mixing Instructions
Basic Calculation
- For 1 mL total volume: 0.9 mL 5-FU + 0.1 mL TA
- For 2 mL total volume: 1.8 mL 5-FU + 0.2 mL TA
- For 5 mL total volume: 4.5 mL 5-FU + 0.5 mL TA
The 9:1 ratio means that for every 10 parts of total mixture, 9 parts are 5-FU and 1 part is TA.
Final Concentrations in the Mixture
- 5-FU concentration: 45 mg/mL (50 mg/mL × 0.9)
- TA concentration: 4 mg/mL (40 mg/mL × 0.1)
Clinical Context
This 9:1 ratio is not the standard mixture used in dermatologic practice for keloids and hypertrophic scars. The evidence base predominantly supports different ratios:
Evidence-Based Ratios for Keloid/Scar Treatment
Most commonly studied and recommended ratios:
- 1:1 ratio (equal volumes): 0.5 mL of each drug 1, 2, 3
- 3:1 ratio (3 parts 5-FU to 1 part TA): Used in validated studies 1
- 9:1 ratio (0.9 mL 5-FU + 0.1 mL TA): Less commonly reported but follows the same mixing principle
The combination of 5-FU and TA demonstrates superior efficacy compared to either agent alone, with odds ratios of 3.45 versus TA monotherapy and 4.17 versus 5-FU monotherapy 4. The combination also reduces telangiectasia risk compared to TA alone (OR 0.24) 4.
Important Caveats
- Verify the intended ratio with the prescribing physician, as 9:1 is unusual for standard keloid treatment
- Use aseptic technique when mixing
- Mix gently to avoid creating air bubbles
- Use immediately after mixing for optimal stability
- The mixture should be administered intralesionally using appropriate needle gauge (typically 25-27 gauge)