What is the concentration of triamcinolone in 1ml of solution after mixing 1ml of 10mg triamcinolone with 3ml of Preservative-Free Normal Saline Solution (PNSS) and then taking 0.5ml of this mixture and adding it to another 0.5ml of PNSS?

Triamcinolone Dilution Calculation

The final 1cc (1mL) solution contains 1.25mg of triamcinolone.

Step-by-Step Calculation

First Dilution

• Starting material: 1mL of 10mg triamcinolone
• Added to: 3mL of PNSS
• Total volume: 4mL
• Concentration after first dilution: 10mg ÷ 4mL = 2.5mg/mL 1

Second Dilution

• Volume taken from first dilution: 0.5mL
• Amount of triamcinolone in 0.5mL: 0.5mL × 2.5mg/mL = 1.25mg
• Added to: 0.5mL of PNSS
• Total final volume: 1mL (0.5mL + 0.5mL)
• Final concentration: 1.25mg/mL 1

Clinical Context

This serial dilution technique follows standard pharmaceutical dilution principles used in preparing injectable medications 1. The final concentration of 1.25mg/mL is well below typical therapeutic doses used for triamcinolone acetonide injections:

• Intra-articular injections: 2.5-40mg per joint depending on size 2
• Intramuscular systemic therapy: 40-80mg per injection 2
• Smaller joints: 2.5-5mg 2
• Larger joints: 5-15mg (up to 40mg for larger areas) 2

Important Considerations

• The original triamcinolone formulation (10mg/mL) is consistent with standard pharmaceutical preparations 2
• Strict aseptic technique must be maintained throughout the dilution process 2
• The suspension should be shaken before use to ensure uniformity and inspected for clumping or granular appearance (agglomeration) 2
• After withdrawal, the diluted solution should be injected without delay to prevent settling 2