How should Lantus (insulin glargine) and NPH (Neutral Protamine Hagedorn) insulin doses and carb ratio be adjusted for a patient on prednisone with improved fasting blood glucose?

Adjusting Insulin Regimen for Patient on Prednisone with Improved Fasting Blood Glucose

For this 108 kg, 63-year-old male on prednisone 60 mg with improving fasting blood glucose of 76 mg/dL, reduce Lantus from 20 units to 16 units (20% reduction) and start morning NPH insulin at 30 units (0.3 units/kg) to manage steroid-induced hyperglycemia with a carbohydrate ratio of 1:10.

Lantus Dose Adjustment

• Reduce the current Lantus dose by 20% (from 20 units to 16 units) due to the improving fasting blood glucose of 76 mg/dL, which indicates risk of hypoglycemia 1
• The low fasting blood glucose (76 mg/dL) suggests the current Lantus dose may be excessive, especially since Lantus primarily controls fasting/overnight glucose levels 2
• Lantus has a relatively constant basal level of circulating insulin with no pronounced peak, which makes it less suitable as the sole insulin for managing steroid-induced hyperglycemia 3

NPH Insulin for Steroid-Induced Hyperglycemia

• Add NPH insulin at 0.3 units/kg (approximately 30 units) to be administered in the morning to match the pharmacokinetic profile of prednisone 4, 5
• Morning administration of NPH is specifically recommended for steroid-induced hyperglycemia as its peak action (4-6 hours) aligns with the peak hyperglycemic effect of glucocorticoids 4
• For patients on high-dose glucocorticoids (60 mg prednisone), higher insulin requirements are common, potentially 40-60% more than standard dosing 4, 5

Carbohydrate Ratio and Monitoring

• Set the carbohydrate ratio at 1:10 to provide adequate insulin coverage for meals, accounting for the insulin resistance caused by high-dose prednisone therapy 5
• Monitor blood glucose before meals and at bedtime to assess the adequacy of the NPH dose and carbohydrate ratio 5
• For persistent hyperglycemia, increase the NPH dose by 2 units every 3 days until target blood glucose is achieved without hypoglycemia 1, 4

Special Considerations for This Patient

• With a high body weight of 108 kg, this patient likely has baseline insulin resistance requiring higher insulin doses 5
• The combination of Lantus and NPH provides better 24-hour coverage: NPH for daytime steroid-induced hyperglycemia and reduced Lantus for overnight control 6
• If hypoglycemia occurs, determine the cause and if no clear reason is found, lower the corresponding insulin dose by 10-20% 1, 4

Adjustments During Steroid Taper

• When prednisone dose is reduced, decrease the NPH dose by 10-20% to prevent hypoglycemia 4
• Focus primarily on reducing the morning NPH dose when tapering morning steroids 4
• Consider switching from NPH back to Lantus-only regimen after complete steroid discontinuation if the patient has frequent hypoglycemia 4

Common Pitfalls to Avoid

• Avoid relying solely on Lantus for steroid-induced hyperglycemia management, as its flat profile doesn't match the daytime hyperglycemic pattern of steroids 4, 6
• Don't underestimate insulin requirements in patients on high-dose steroids; inadequate dosing leads to persistent hyperglycemia 4, 5
• Be vigilant for nocturnal hypoglycemia with the combined insulin regimen, especially with the improving fasting glucose 2, 7