Interactive diabetes case 2: Switching from oral agents to insulin in type 2 diabetes – B3

ANSWER — 

Correct.

The patient needs more insulin. Assuming conservatively a dose requirement of 0.8 units/kg for a patient with obesity and type 2 diabetes, the estimated dose requirement is 72 units per 24 hours for this patient.

Several weeks later, the patient returns. She is taking NPH 55 units at bedtime. The fasting glucose level is 135 to 145 mg/dL (7.5 to 8.0 mmol/L). Pre-meal and bedtime glucose levels are 160 to 170 mg/dL (8.9 to 9.4 mmol/L). The patient is again encouraged to increase the dose of NPH insulin at bedtime incrementally. When the dose is 75 units at bedtime, the fasting glucose value is usually 110 to 120 mg/dL (6.1 to 6.7 mmol/L); the pre-meal and bedtime glucose levels are usually 125 to 135 mg/dL (6.9 to 7.5 mmol/L). Over the next three months, the glycated hemoglobin (A1C) value falls to 7.1 percent.

You stop the glipizide since the patient is on a full dose of exogenous insulin, and little or no benefit will accrue from stimulating endogenous insulin. You continue the metformin, which the patient has tolerated well, to minimize weight gain and for its beneficial effects on hepatic glucose production, circulating lipid levels in patients with the metabolic syndrome, and decreased risk of cardiovascular events and death.

Alternatively, you could have stopped the sulfonylurea (glipizide) when you initially added insulin. Some prefer this approach. However, the glucose levels may rise in the ensuing weeks until the dose of injected insulin is sufficient to achieve glycemic targets. This may be disheartening to the patient and may on occasion cause or worsen symptoms of hyperglycemia. This approach should probably be limited to those settings where you or a qualified member of your staff (eg, a diabetes nurse educator) will be in frequent communication (every five days or so) with the patient to facilitate rapid increases in the dose of insulin and to address a rise in the glucose level if it occurs. This consultant prefers the approach used in this case study.

Good work.

However, you discover in cross-coverage that your colleagues have treated similar patients differently with comparable results. To explore the consequences of the other actions, return to the case at the beginning of this sequence. (See "Interactive diabetes case 2: Switching from oral agents to insulin in type 2 diabetes".)

For additional information, see the comment at the end of this sequence. (See "Interactive diabetes case 2: Switching from oral agents to insulin in type 2 diabetes – Comment".)