What should be the Lantus (insulin glargine) dose, carb ratio, and correction scale for a male patient with type 2 diabetes, currently on Soliqua 30 (lixisenatide and insulin glargine) daily, who is starting CAR-T therapy?

Transitioning from Soliqua to Lantus for CAR-T Therapy

For a patient on Soliqua 30 units daily starting CAR-T therapy, discontinue Soliqua and initiate Lantus at 30 units once daily, with aggressive titration by 4 units every 3 days targeting fasting glucose 80-130 mg/dL, using a carbohydrate ratio of 1:10 and correction factor of 1:30-50 mg/dL. 1, 2

Rationale for Lantus Dose Selection

The 30-unit Lantus dose directly corresponds to the insulin glargine component in Soliqua 30 units (which contains 30 units insulin glargine + 10 mcg lixisenatide). 2 Since CAR-T therapy creates acute metabolic stress requiring simplified insulin management without GLP-1 RA components, this provides continuity of basal coverage while eliminating the lixisenatide component. 1, 3

Expected Insulin Requirements During CAR-T

• CAR-T therapy induces acute illness and inflammatory stress, typically requiring 40-60% increases in insulin doses beyond baseline requirements. 1
• For this patient's weight, total daily insulin requirements during acute stress may reach 0.4-0.6 units/kg/day, suggesting eventual needs of 40-60+ units daily as basal insulin. 1
• Aggressive upward titration by 4 units every 3 days is appropriate when fasting glucose remains ≥180 mg/dL, which is likely during CAR-T-induced hyperglycemia. 1

Carbohydrate Ratio Calculation

Start with a 1:10 carbohydrate-to-insulin ratio (1 unit of rapid-acting insulin covers 10 grams of carbohydrate). 1

Calculation Method

• Using the 500 rule: 500 ÷ estimated total daily dose (TDD) = carb ratio 1
• With starting TDD of approximately 50 units (30 basal + estimated 20 units prandial): 500 ÷ 50 = 1:10 ratio 1
• This ratio should be reassessed every 3-7 days based on 2-hour postprandial glucose readings, adjusting by 10-20% if consistently out of target. 1

Correction Scale (Insulin Sensitivity Factor)

Use an insulin sensitivity factor of 1:30-50 mg/dL (1 unit of rapid-acting insulin lowers glucose by 30-50 mg/dL). 1

Calculation Method

• Using the 1500 rule: 1500 ÷ TDD = insulin sensitivity factor 1
• With TDD of 50 units: 1500 ÷ 50 = 1:30 mg/dL 1
• For patients with higher insulin resistance during acute illness, use the more conservative 1:50 factor initially to minimize hypoglycemia risk. 1

Correction Dose Algorithm

• Target glucose: 100-140 mg/dL for hospitalized/acutely ill patients 4
• If pre-meal glucose is 200 mg/dL with target of 120 mg/dL: (200-120) ÷ 30 = 2.7 units correction dose 1
• Avoid "stacking" corrections within 3-4 hours of previous rapid-acting insulin dose. 1

Prandial Insulin Requirements

Add rapid-acting insulin (lispro, aspart, or glulisine) at 4 units before each meal initially, then titrate based on postprandial glucose patterns. 1, 3

Prandial Dosing Strategy

• Start with 4 units before the largest meal or 10% of basal dose (3 units in this case, round to 4 units). 1
• Titrate prandial doses by 1-2 units every 3 days based on 2-hour postprandial glucose readings. 1
• During CAR-T therapy with poor oral intake, reduce or hold prandial insulin but maintain basal insulin at reduced dose (20-25% reduction). 1

Critical Monitoring During CAR-T Therapy

Glucose Monitoring Frequency

• Check fasting glucose daily for basal insulin titration. 1, 3
• Check pre-meal and 2-hour postprandial glucose for prandial insulin adjustment. 1
• During acute CAR-T complications (cytokine release syndrome, neurotoxicity), increase monitoring to every 4-6 hours or consider continuous glucose monitoring. 4

Dose Adjustment Triggers

• If fasting glucose ≥180 mg/dL: Increase Lantus by 4 units every 3 days. 1
• If fasting glucose 140-179 mg/dL: Increase Lantus by 2 units every 3 days. 1
• If any hypoglycemia <70 mg/dL occurs: Reduce Lantus by 10-20% immediately and reassess carb ratio/correction factor. 1, 3

Special Considerations for CAR-T Therapy

Steroid-Induced Hyperglycemia

• If high-dose corticosteroids are initiated for cytokine release syndrome, increase total daily insulin by 40-60% or more, with proportionally greater increases in prandial/correction insulin. 1
• Consider adding NPH insulin in the morning to match steroid-induced daytime hyperglycemia pattern. 1

Poor Oral Intake Management

• Maintain basal insulin at 80% of usual dose even with minimal oral intake to prevent diabetic ketoacidosis. 1
• Hold or significantly reduce prandial insulin (to 25-50% of usual) when meals are not consumed. 1
• Use correction insulin more liberally to address stress-induced hyperglycemia. 1

Renal Function Monitoring

• If eGFR declines <45 mL/min/1.73m² during CAR-T complications, reduce total insulin doses by 25% due to decreased insulin clearance. 4
• Metformin should be discontinued if eGFR <30 mL/min/1.73m². 4

Foundation Therapy Continuation

Continue metformin at current dose (or optimize to 1000 mg twice daily) unless contraindicated by renal dysfunction, acute illness with lactic acidosis risk, or contrast procedures. 1, 3 Metformin reduces insulin requirements by 20-30% and should be maintained throughout CAR-T therapy when medically appropriate. 1

Common Pitfalls to Avoid

• Do not delay aggressive insulin titration during CAR-T-induced hyperglycemia—this patient will likely need 50-80+ units of Lantus within 2-3 weeks. 1
• Do not rely solely on correction insulin (sliding scale)—scheduled basal-bolus regimens are superior for preventing hyperglycemia. 1
• Do not continue escalating Lantus beyond 0.5 units/kg/day (approximately 50 units for this patient's weight) without ensuring adequate prandial coverage. 1
• Do not use the same correction factor throughout the day—morning insulin resistance may require a lower sensitivity factor (1:40) versus evening (1:50). 1