Clinical & Hospital Pharmacy
Reconstitution & IV Compounding Calculator
Works out diluent volume, yield concentration and the syringe volume for a parenteral vial, then the carrier bag dilution and smart-pump rate.
Educational tool — verify against the package insert
Syringe volume to withdraw
7.50mL
Yields 750.0 mg (75.0% of vial)
Module
Drug
Pick a monograph to load its vial strength, displacement and standard diluent.
Ceftriaxone (Rocephin)
Diluents: Sterile Water for Injection (SWFI), 0.9% Sodium Chloride (NS), 5% Dextrose (D5W)
Stability — room temp: 2 days (25°C) · refrigerated: 10 days (4°C)
CONTRAINDICATION: Do NOT mix or co-infuse with calcium-containing IV solutions (e.g., Lactated Ringer's) due to risk of fatal calcium-ceftriaxone crystalline precipitation in lungs/kidneys.
DailyMed monographCalculation mode
Vial & diluent
Powder displacement is what makes the yield volume exceed the diluent added.
Labelled active drug per vial.
Volume the dry powder itself occupies (USP <797>).
Yields 10.00 mL total solution.
Ordered dose on the prescription.
Compounding output
The full reconstitution record.
The powder itself takes up space, so the final volume is the diluent plus the displacement:
final volume = diluent added + powder displacement
concentration = total drug in vial / final volume
From there the syringe volume follows directly, or the dose in a measured volume:
volume to withdraw = dose / concentration
delivered dose = volume withdrawn × concentration
Working the other way, to hit a target concentration:
diluent = (vial strength / target concentration) − displacement
For the secondary bag, the drug volume adds to the carrier:
total IVPB volume = carrier volume + syringe volume
pump rate (mL/hr) = total volume / duration (min) × 60
Doses are converted to milligrams before any division, and the vial fraction used is the syringe volume as a percentage of the total yield.
Keep learning
References
- Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.
Common questions
Because it changes the concentration. Adding 9.6 mL to a 1 g ceftriaxone vial with 0.4 mL displacement gives 10 mL at 100 mg/mL. Assuming 9.6 mL final volume would give 104 mg/mL, and every dose drawn from the vial would be about 4% short.
In the package insert, usually in the reconstitution table as the difference between the diluent volume and the stated yield. It is product- and manufacturer-specific, so the values preloaded here are typical rather than authoritative.
Yes, when the drug is added into the carrier bag — a 100 mL bag plus a 22.4 mL syringe infuses 122.4 mL, and programming the pump for 100 mL would leave part of the dose behind. Some institutions use a fixed overfill allowance instead; follow local policy.
No. Several of these drugs are incompatible with particular solutions — ceftriaxone must never meet a calcium-containing fluid such as Lactated Ringer's. Use only the diluents listed on the monograph for the product.
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