How should the Lantus (insulin glargine) dose and carb ratio be adjusted for a 75kg patient with a BMI of 32 receiving dexamethasone 12mg IV to manage potential hyperglycemia?

Management of Insulin Therapy for Patient on Dexamethasone

For a 75kg patient with BMI 32 receiving dexamethasone 12mg IV, initiate Lantus at 22.5 units once daily (0.3 units/kg) and use a carbohydrate ratio of 1:10 (1 unit of insulin for every 10g of carbohydrate) with appropriate correction doses for hyperglycemia. 1, 2

Rationale for Insulin Management with Dexamethasone

Dexamethasone 12mg IV is a high-dose glucocorticoid that will significantly impact glycemic control through multiple mechanisms:

• Increases insulin resistance
• Impairs beta cell insulin secretion
• Enhances hepatic gluconeogenesis
• Causes predominantly afternoon and evening hyperglycemia (peaks 7-9 hours after administration) 1, 3

Specific Insulin Regimen

Basal Insulin (Lantus)

• Starting dose: 22.5 units once daily (calculated as 0.3 units/kg for 75kg patient) 1
• Administer in the evening to counteract dexamethasone-induced afternoon/evening hyperglycemia
• Monitor fasting glucose levels and adjust by 2-4 units every 3 days until target is achieved 2

Prandial Insulin Management

• Carbohydrate ratio: 1:10 (1 unit of insulin for every 10g of carbohydrate) 1, 2
• This ratio may need to be more aggressive (e.g., 1:8) for lunch and dinner when dexamethasone effect is strongest 1

Correction Factor

• Start with correction factor of 1:50 (1 unit lowers glucose by 50 mg/dL) 2
• Apply the following correction scale:
  • BG 150-200 mg/dL: Add 2 units
  • BG 201-250 mg/dL: Add 4 units
  • BG 251-300 mg/dL: Add 6 units
  • BG >300 mg/dL: Add 8 units and notify provider 2

Monitoring and Adjustments

• Check blood glucose before meals and at bedtime
• Pay particular attention to afternoon and evening glucose levels when dexamethasone effect peaks 1
• Expect insulin requirements to be significantly higher than usual while on dexamethasone 4
• Be prepared to use up to 122 ± 39 units/day of total insulin for adequate glycemic control during high-dose dexamethasone therapy 4

Important Considerations

• A basal-bolus insulin regimen is superior to sliding scale insulin alone for managing dexamethasone-induced hyperglycemia 4
• For patients with pre-existing diabetes, the distribution of insulin should shift to approximately 25% basal and 75% prandial while on dexamethasone 1, 2
• Monitor for rapid decline in insulin requirements when dexamethasone is discontinued to avoid hypoglycemia 1
• Consider more frequent monitoring during the first 24-48 hours of dexamethasone therapy as insulin requirements may increase rapidly 5

Hypoglycemia Prevention

• Educate on hypoglycemia recognition and management
• Ensure patient has access to fast-acting carbohydrates (15-20g) for treating hypoglycemia 2
• Consider prescribing glucagon for emergency hypoglycemia management

Implementing this structured insulin regimen will help maintain glycemic control and reduce the risk of complications associated with dexamethasone-induced hyperglycemia, ultimately improving patient outcomes 5.