Answer: D. If creatinine clearance is > 50 mL/min, dose adjustment is not necessary and the maximum dosage of sitagliptin is 100 mg by mouth once daily. If creatinine clearance is 30 to 50 mL/min, it is appropriate to reduce dosage of sitagliptin to 50 mg by mouth once daily. In our patient with a creatinine clearance < 30 mL/min reflective of severe renal insufficiency, a dosage of 25 mg by mouth once daily is appropriate.

Outcomes

The patient’s HbA1c was 7.4% at the time of his visit. There were concerns about anemia (his hemoglobin level was 8.3 g/dL at time of HbA1c evaluation, and it was felt that this HbA1c value was not an accurate picture of his diabetes control). He reports that his glucometer is broken, and he has not been checking his glucose values recently. He is given a new prescription for a glucometer and metering supplies. He is advised to test his glucose values twice daily prior to eating meals. Arabic language record books for logging glucose results are provided. A follow-up appointment is requested in 1 month to review these results. Until that time, he agrees to continue with sitagliptin 25 mg by mouth once daily. This medication typically does not cause hypoglycemia, but the patient stated that he would take it with his first meal of the day consumed during Ramadan.

At his return visit, the patient brought his record book. He was adherent to twice-daily blood glucose testing. Review of this record book revealed that his glucose values were consistently above 200 mg/dL. The patient agreed to resume insulin therapy to improve his glycemic control. Given his elevated creatinine level, a low dosage of NPH insulin once daily was prescribed, to be taken with the first meal of the day. He also worked with a diabetes educator to learn about insulin dose adjustments to improve glycemic control. 

Jennifer A. Grenell, APRN, CNP, practices at the Mayo Clinic department of endocrinology, specializing in diabetes management.