NAPLEX Question of the Week: Diabetes and Days Supply

Calculating days supply is a daily part of community pharmacy practice. Are you up for this week's challenge?

Like Comment

LZ is a 56 year old female with a history of hypertension, Type 2 diabetes, and hyperlipidemia is in your pharmacy today. The patient is currently on metformin 1000 mg PO twice daily, Victoza 1.8 mg SQ daily, Tresiba 28 units SQ daily, lisinopril 20 mg PO daily, atorvastatin 40 mg PO daily and Apidra 3 units SQ three times daily with meals and 1 unit SQ once daily with snacks. LZ is picking up 3 Tresiba 100 unit/mL pens and 3 Apidra 100 unit/mL pens. Calculate the days supply LZ is picking up today for both Tresiba and Apidra. 

A. Tresiba: 10 days supply; Apidra 90 days supply

B. Tresiba: 10 days supply; Apidra 84 days supply

C. Tresiba: 32 days supply; Apidra 90 days supply

D. Tresiba: 32 days supply; Apidra 84 days supply

 

Answer with rationale: 

Answer D is correct.

Insulin is commonly dispensed in community pharmacies and due to ease of administration, many patients prefer insulin pens over vials. Tresiba, or insulin degludec, is a long acting basal insulin that is available in 10 mL vials (100 unit/mL) and 3 mL pens (100 units/mL and 200 units/mL). Both the Tresiba vials and the pens can be stored at room temperature once punctured for up to 56 days. LZ is using 28 units daily and is picking up a total of 3 pens which is equivalent to a 32 days supply, making Answer A and B incorrect. The math is shown below.

 

Tresiba

1 pen = 3 mL x 100 units/mL = 300 units/pen

300 units/28 units daily = 10.71 days supply/pen

10.71 days supply/pen x 3 pens = 32.14 days supply = 32 days supply

 

LZ is also using Apidra (insulin glulisine) which is a rapid acting insulin. Apidra is only available in 10 mL vials and 3 mL pens with a 100 units/mL concentration. Apidra pens and vials can be stored refrigerated up to the expiration date on the box, but once punctured each pen has a beyond-use date (BUD) of 28 days whether at room temperature or refrigerated. LZ is using a total of 10 units daily and is picking up a total of 3 pens. Each pen contains 300 units which should last LZ 30 days however due to the 28 day BUD of each pen once opened, the 3 pens will only last LZ 84 days, making Answer C incorrect. The math is shown below.

 

Apidra

1 pen = 3 mL x 100 units/mL = 300 units/pen

300 units/10 units daily = 30 days supply/pen = 28 day supply/pen (due to BUD)

28 days supply/pen x 3 pens = 84 days supply

 

Knowing the storage information for each insulin formulation is an important part of counseling patients when dispensing insulin. When studying for the NAPLEX, many students find it helpful to create a chart comparing all the insulin formulations. Patients should also be counseled on the proper administration techniques (ie. rotating injection sites), signs of hyper- and hypoglycemia, and the importance of adherence.

Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

No comments yet.