What is the recommended dosing strategy when converting a patient from NPH (Neutral Protamine Hagedorn) insulin to Lantus (insulin glargine)?

NPH to Lantus (Insulin Glargine) Conversion

When converting from NPH to Lantus, use a 1:1 unit-for-unit conversion if switching from once-daily bedtime NPH, or reduce the total daily NPH dose by 20% (use 80% of total NPH dose) if converting from twice-daily NPH to once-daily Lantus to minimize hypoglycemia risk. 1

Conversion Strategy Based on NPH Regimen

From Once-Daily Bedtime NPH

• Convert unit-for-unit (1:1 ratio) when switching from once-daily bedtime NPH to once-daily Lantus 2, 3
• Administer Lantus at bedtime initially, though it can be given at any time of day once stable 4
• The initial dose should match the previous NPH dose without reduction 2

From Twice-Daily NPH

• Use 80% of the total daily NPH dose when converting from twice-daily NPH to once-daily Lantus 1
• This reduction accounts for Lantus's more consistent pharmacokinetic profile and lower peak effect, reducing hypoglycemia risk 5
• For example: if a patient takes 20 units NPH twice daily (40 units total), start Lantus at 32 units once daily 1

Timing Considerations

• Morning administration of Lantus is preferred when converting from bedtime NPH in patients with type 2 diabetes on basal-prandial therapy 2
• Morning dosing allows better monitoring during waking hours and reduces nocturnal hypoglycemia risk 6
• One study demonstrated superior glycemic control (HbA1c 6.6% vs 6.9%, p=0.007) when converting bedtime NPH to morning Lantus without increasing total insulin dose 2

Titration Protocol After Conversion

• Set a fasting plasma glucose target <100 mg/dL (<5.5 mmol/L) to achieve HbA1c <7% 7
• Increase Lantus by 2 units every 3 days until reaching target fasting glucose without hypoglycemia 1, 7
• If hypoglycemia occurs, reduce the dose by 10-20% 1, 8
• More aggressive titration (increase by 4-8 units based on glucose levels) can be used if fasting glucose remains significantly elevated 7

Key Advantages of Lantus Over NPH

• Lower nocturnal hypoglycemia rates: Most clinical trials demonstrate significantly fewer nocturnal hypoglycemic episodes with Lantus compared to NPH 5
• Peakless profile: Lantus provides approximately 24 hours of basal coverage without pronounced peaks, unlike NPH's 4-6 hour peak 4, 5
• Once-daily dosing: Simplifies regimen compared to twice-daily NPH, improving adherence 4

Special Populations and Considerations

Patients with Renal Impairment

• Start conservatively with 80% of previous NPH dose due to decreased insulin clearance and increased hypoglycemia risk 6
• Consider more frequent glucose monitoring during initial titration 6
• Morning administration is particularly beneficial to allow better daytime monitoring 6

Insulin-Resistant or Obese Patients

• May require higher doses (up to 50% of total daily insulin as basal) to achieve glycemic targets 2
• Consider twice-daily Lantus if very high volumes are needed, though this is less common 4

Common Pitfalls to Avoid

• Do not mix Lantus with other insulins in the same syringe: Lantus coprecipitates with short-acting insulins, requiring separate injections 4
• Do not reduce dose when converting from once-daily NPH: Only reduce when converting from twice-daily NPH 1, 2
• Monitor for overbasalization: If Lantus dose exceeds 0.5 units/kg/day with persistent hyperglycemia, consider adding prandial insulin or GLP-1 RA rather than further increasing basal dose 1
• Adjust prandial insulin if needed: Lantus does not treat postprandial hyperglycemia; ensure adequate mealtime insulin coverage 4

Monitoring Requirements

• Check fasting glucose daily during titration phase 7
• Assess adequacy of basal insulin by evaluating bedtime-to-morning glucose differential and presence of hypoglycemia 1
• Consider glucagon prescription for emergent hypoglycemia, especially in high-risk patients 1