Beware of the New Problem with the Updated Online Santyl® Calculator

Santyl® ointment 250 units/gram is a topical medication indicated for debriding chronic dermal ulcers and severely burned areas. This medication is frequently targeted by auditors because correctly calculating the quantity needed and days’ supply requires knowledge about the wound size and treatment duration.

Prior to the recent update to the Santyl® online calculator, only the quantity needed for one wound could be calculated at a time and the total amount of ointment needed was rounded to the nearest 30 g or 90 g increment since these are the two commercially available package sizes. This led to an increased risk of overbilling and incorrect days’ supply calculations as previously discussed in the October 2021 Newsline article, Santyl® Dosing Calculator—Manufacturer’s Rounding May Lead to Recoupment.

Now, the calculator can determine the amount of ointment needed for more than one wound at a time and it provides the exact amount needed for the wound, or wounds, and specified treatment duration. However, what is not addressed with the online calculator is that once the pharmacy selects the total amount to dispense based on a 30 g or 90 g tube (or multiples thereof) the days’ supply may need to be recalculated to account for the extra dispensed which is necessary to accommodate the commercially available package sizes.

To determine the correct days’ supply, follow the example below:

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Prescription: Santyl® ointment qs 20 days with zero refills; sig: apply to affected area(s) once daily; wound #1 is 5 cm x 2 cm, wound #2 is 3 cm x 1 cm

Online Calculator: After inputting the wound length and width for each of the two wounds and the 20-day treatment duration, you will see that 45 g would be needed. However, the pharmacy can only choose from a 30 g tube or 90 g tube (or multiples thereof) when dispensing, therefore, the calculator states that two of the 30 g tubes, or 60 g total, would be needed.

Manual Days’ Supply Calculation: Since the pharmacy must dispense 60 g to provide the patient with enough ointment to finish their course of treatment, the pharmacy must calculate the true days’ supply for all 60 g dispensed. To do this, you must:

  1. Convert the total number of centimeters needed per wound per day, to grams. The online calculator provides the total number of centimeters of ointment needed for each application for each wound. Based on our example above, wound #1 requires 5.2 cm/application and wound #2 requires 1.6 cm/application for a total of 6.8 cm once daily.
  2. Using the cm-to-g conversion factor found in the calculator by clicking “How is this calculated?”, you will see 3.04 cm from a 30 g tube is approximately 1 g. Therefore 6.8 cm divided by 3.04 cm per 1 gm = 2.2 g per day.
  3. Determine the days’ supply for the 60 g dispensed by dividing 60 g by 2.2 g per day = 27 days.

PAAS Tips:

  • Every Santyl® ointment prescription requires the wound size (length and width in centimeters), the treatment duration, and the use of the online calculator
    • Wounds should be decreasing in size overtime, therefore, updated wound sizes are needed if refilling Santyl®
    • If you are calling the prescriber’s office to obtain wound information, be sure a full clinical note is documented including:
      • date of the call
      • name (and title) of the person you spoke with
      • the clarification
      • initials of who made the call
    • Maintain a copy of the calculator results with the Santyl® prescription in case of an audit
    • Manual days’ supply calculations are often still needed
    • The cm-to-g conversion factor is not the same for a 30 g tube and 90 g tube
      • From a 30 g tube, a length of 3.04 cm is equivalent to approximately 1 g
      • From a 90 g tube, a length of 1.78 cm is equivalent to approximately 1 g


Sara Hathaway, PharmD