Calculating Days SupplyThe days supply calculation is one you will be making for each and every prescription you fill as a pharmacy technician. In most cases, “Days Supply” is calculated by dividing the maximum amount of the medication used in 1 day by the dispensed amount. “Days Supply” means just what it sounds like: it is how many days the supply of dispensed medication will last. Here are a couple of examples: Example #1 Motrin (ibuprofen) 800mg, 1 tablet 3 times daily as needed, #30. Days supply takes the maximum amount the patient could take in 1 day, in this case 3 tablets, divided into the amount dispensed of 30 pills- 30/3=10 days supply. Example #2 Toradol (ketorolac) 10mg, 1 tablet every 4-6 hours as needed, not more than 4 per day. #80. Max amount per day=4 divided by 80=20 days supply. 
Example #3Celexa (citalopram) 40mg, 1 tablet daily, #30. 30/1=30 days supply. These previous examples seem straightforward, but it gets a bit more complicated when you are dealing with other types of prescriptions. Calculating Ear Drop and Eye Drop Days Supply are different than the example problems above. Usually with ear and eye drops, 1ml (1 milliliter) will have 20 drops of medication. Time for another example. Example #4 Tobramycin Eye Suspension, 1 drop into each eye 3 times daily, 5ml bottle. 1 drop into each eye=2 drops X 3 times daily = 6 drops per day. 5ml X 20 drops per mL = 100 drops total. 100 drops / 6 drops per day = 16.6 Note: In this case the days supply is not a round number. Most pharmacy computer systems are unable to take a decimal number like 16.6. In this case you should round the number down to the nearest round number. So the answer to this example would be 16 days supply. 
Topical Agents: Creams, Ointments, Gels, Pledgets, Topical Solutions, and Powders, are also different from our previous examples. Usually as a rule, the days supply on these are between 7-10 days. This is not an exact calculation. Or, if the physician indicates the days supply on the prescription, then your are all set, you have been given your days supply.Example #5 Triamcinolone Cream .01%, Apply to Affected Area on Hand As Needed, 30 gram tube. Days supply=7-10 days Liquids: Solutions, Suspensions, Syrups Robutussin AC Syrup: Take 1 Teaspoonful Every 6 Hours As Needed for Cough, 4oz. With Liquids, we are back to calculating days supply mathematically using our formula as in examples #1-4. In this example, you need to be able to convert Ounces to ML. There are 30 ML in 1 Oz., so 4 Oz = 120 ML. There are 5ML’s in 1 Teaspoonful. The maximum the patient could take in one day is 5ML times 4 (24 hours in 1 day, divided by 6 = 4) = 20ml used in one day. 120ML divided by 20ML = 6 Days Supply Hopefully these examples have clarified for you how to calculate days supply! Top of Days Supply
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