How to manage insulin for a patient on glucocorticoid therapy who is already taking Lantus (insulin glargine)?

Managing Insulin for Patients on Glucocorticoid Therapy Who Are Already Taking Lantus

For patients on glucocorticoid therapy who are already taking Lantus (insulin glargine), add NPH insulin in the morning to match the peak hyperglycemic effect of glucocorticoids while maintaining the Lantus dose for basal coverage. 1, 2

Understanding Glucocorticoid Effects on Blood Glucose

• Glucocorticoids induce hyperglycemia through multiple mechanisms: impaired beta cell insulin secretion, increased insulin resistance, and enhanced hepatic gluconeogenesis 2
• The hyperglycemic pattern is most pronounced during the day (particularly afternoon and evening) and often normalizes overnight, creating a mismatch with the flat profile of Lantus 3, 2
• Glucocorticoid therapy can induce hyperglycemia in 56-86% of hospitalized patients with and without preexisting diabetes 1
• The degree of hyperglycemia directly correlates with the glucocorticoid dose - higher doses cause more significant elevations in blood glucose 2

Insulin Management Strategy

Maintain Lantus and Add NPH Insulin

• Continue the patient's Lantus (insulin glargine) for baseline 24-hour basal insulin coverage 3, 4
• Add NPH insulin in the morning to match the peak hyperglycemic effect of glucocorticoids 1, 5
• Initial NPH insulin dosing should be 0.1-0.2 units/kg per day administered in the morning to coincide with glucocorticoid administration 1
• For patients on high-dose glucocorticoids, increase insulin requirements by 40-60% above standard dosing 1, 2

Dosing Adjustments

• For patients already on insulin, increase total daily insulin dose by 30-50% during steroid treatment 5
• For persistent hyperglycemia, increase NPH dose by 2 units every 3 days until target blood glucose is achieved 1, 5
• For long-acting glucocorticoids such as dexamethasone, consider increasing the Lantus dose in addition to adding NPH insulin 3, 2

Monitoring Protocol

• Monitor blood glucose four times daily (fasting and 2 hours after each meal) 2
• Pay special attention to afternoon and evening glucose values, which tend to be highest with morning steroid administration 1, 5
• Target blood glucose range should be 100-180 mg/dL (5.6-10.0 mmol/L) 3, 1

Special Considerations

Type of Glucocorticoid

• For short-acting glucocorticoids like prednisone (peak plasma levels in 4-6 hours), NPH insulin is particularly effective due to its matching pharmacokinetic profile 3, 5
• For long-acting glucocorticoids like dexamethasone, a higher dose of Lantus may be required in addition to NPH insulin 3, 2

Steroid Tapering

• As steroid doses are reduced, insulin doses should be proportionally decreased to avoid hypoglycemia 2, 5
• Insulin requirements typically decrease rapidly after steroid discontinuation, requiring prompt dose adjustments 1

Common Pitfalls to Avoid

• Relying solely on sliding scale insulin is ineffective for managing glucocorticoid-induced hyperglycemia 1
• Using only fasting glucose to monitor steroid-induced hyperglycemia will miss the peak hyperglycemic effect 2
• Not reducing insulin doses when steroid doses are tapered can lead to hypoglycemia 2, 5
• Failing to anticipate the diurnal pattern of steroid-induced hyperglycemia, with peak effects in the afternoon and evening 2

Practical Example

• For a 70kg patient on prednisone 40mg daily who is already taking Lantus 20 units at bedtime:
  • Continue Lantus 20 units at bedtime
  • Add NPH insulin 10-14 units (0.15-0.2 units/kg) in the morning
  • Monitor blood glucose four times daily and adjust NPH dose by 2 units every 3 days until target is achieved 1, 5