NAPLEX® Review Question of the Week: Delving into Dexcom

This week's question will test a rapidly growing device used within diabetes management.
NAPLEX® Review Question of the Week: Delving into Dexcom
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SW, a 63-year-old female, presented to your ambulatory care clinic for her diabetes care. She recently heard about Dexcom G7. She thinks that she would benefit from one because she fears she is experiencing low blood sugar. She brought in a prescription for Dexcom for you to help her set it up.

Medications:

Humalog 4 units SQ 15 minutes before each meal

Levemir 30 units SQ at bedtime

Glucophage 500 mg PO BID with meals

Hyzaar 50-12.5 mg PO once daily

Tylenol 1000 mg PO q6h

Percocet 5mg/325mg q6h prn (takes 2 tablets daily for breakthrough pain)

PMH:

T2DM

HTN

Osteoarthritis

Vitals:

Wt: 163 lb

Ht: 5’4’’

BP: 127/83 mmHg

Pulse: 64 BPM

Last A1c: 7.2%

FSBG: 85 mg/dL

What are appropriate counseling points for SW? Select all that apply. 

A. SW should remain in the 80-180 mg/dL blood glucose range approximately 70% of the time

B. The Dexcom G7 sensor is functional for 14 days

C. SW may experience falsely elevated glucose readings due to a medication-sensor interaction

D. The Dexcom should not differ by more than 20% from a fingerstick glucose reading if 80mg/dL or higher

E. SW should remove her Dexcom sensor prior to swimming in her pool.

Answers with Rationale:

Continuous glucose monitors (CGMs) have been a gamechanger for patients with diabetes. CGMs measure roughly 250 blood sugar readings daily. A small filament is inserted into the interstitial fluid, usually on the back of the arm. CGMs measure the glucose in the interstitial fluid instead of the blood, which allows for a small delay for the CGMs recording of glucose levels. Most CGMs usually use an arrow to indicate the trend in which the blood sugar is heading to help dissipate the delay in glucose levels. A pharmacist’s role is crucial in educating patients of setup, goals, and maintenance of patient’s CGMs. 

Answer A is correct. Most patients' time in range (80-180 mg/dL) should be greater than or equal to 70%. Patients should have less than 4% time in the range of <70 mg/dL and less than 20% of time in the above range of >250 mg/dL.

Answer B is incorrect. The Dexcom G7 and G6 sensors last for 10 days with a 12-hour grace period. The Freestyle Libre 2 and 3 sensors last for 14 days.

Answer C is correct. SW’s acetaminophen dose is currently 4gm daily scheduled plus 650mg used as needed for total of 4650mg daily. The Dexcom sensor has an interaction with acetaminophen that may lead to falsely high readings. SW should have her acetaminophen total dose below 4gm daily to limit hepatic damage long-term as well as eliminate the drug-sensor interaction. Opiates in general are not optimal for osteoarthritis pain and other drug classes should be used if possible to prevent opioid dependence. 

Answer D is correct. The FDA requires CGMs to be within 20% of a true lab measurement if 80mg/dL or higher. If blood sugar is 80mg/dL or lower, it should be within 20mg/dL of reading. Patients should always verify with a fingerstick if they are having symptoms of hypoglycemia or hyperglycemia if they believe their CGM is incorrect.

Answer E is incorrect. All new CGMs can be used while swimming. The only recommendation to take it off is for deep sea diving.

Brand/Generics Covered:

Insulin Lispro (Humalog), Insulin detemir (Levemir), Metformin (Glucophage), Losartan-Hydrochlorothiazide (Hyzaar), Acetaminophen (Tylenol), Oxycodone-Acetaminophen (Percocet)

Naplex Competencies Covered:

1.1 From instruments, laboratory

1.2 Medication history

1.6 Risk factors or maintenance of health and wellness

2.2 Brand, generic

3.2 Therapeutic goals

3.4 Duration of therapy

3.5 Delivery systems

3.8 Drug interactions

5.4 Equipment or delivery systems

5.5 Instructions for drug administration

5.6 Handling

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