What is the difference between insulin Novalog (insulin aspart) and Lispro (insulin lispro)?

Differences Between Insulin Novolog (Aspart) and Lispro

Both insulin Novolog (aspart) and Lispro are rapid-acting insulin analogs with very similar pharmacokinetic profiles, but insulin aspart may have slightly faster absorption and higher peak concentrations compared to insulin lispro, though this difference has minimal clinical significance in most patients. 1

Pharmacokinetic Comparison

Similarities

• Both are rapid-acting insulin analogs
• Both have:
  • Onset: 5-15 minutes after injection
  • Peak effect: 1-2 hours
  • Duration: 3-5 hours
  • Both should be administered immediately before meals 2

Differences

• In direct comparison studies, insulin aspart showed:
  • Slightly faster absorption
  • Higher peak insulin concentrations (24.6 ± 1.3 mU/L vs. 20.8 ± 1.1 mU/L for lispro) 1
  • Slightly lower glucose concentrations at 50 minutes post-injection (3.2 ± 0.1 mmol/L vs. 3.5 ± 0.1 mmol/L for lispro) 1

Clinical Implications

Despite these minor pharmacokinetic differences, most clinical guidelines and studies indicate that:

• Both insulins are equally effective in controlling postprandial glucose excursions 3
• Both have similar effects on carbohydrate and fat metabolism 3
• Both have comparable safety profiles and rates of hypoglycemia 4, 5
• Both offer advantages over regular human insulin including:
  • Faster onset of action
  • Earlier and greater insulin peak
  • More rapid post-peak decrease 6
  • Better postprandial glycemic control 4

Practical Considerations

Formulations

• Both are available in:
  • Standard vials (100 units/mL)
  • Prefilled pens
  • Cartridges for insulin pumps

Premixed Formulations

• Novolog is available as 70/30 aspart mix
• Lispro is available as 75/25 or 50/50 lispro mix 7

Interchangeability

• While technically interchangeable in most clinical scenarios, patients should maintain consistency with one product when possible
• Switching between products may require minor dose adjustments in sensitive patients

Clinical Pitfalls to Avoid

• Don't delay meals after injection of either insulin - both should be administered immediately before eating
• Don't interchange dosing without monitoring - while similar, individual patient response may vary
• Don't assume complete interchangeability in insulin pumps - some patients may notice subtle differences in absorption rates
• Remember that both insulins have a shorter duration than regular human insulin, which may require more frequent dosing or combination with longer-acting insulins

In summary, while insulin aspart and lispro have minor pharmacokinetic differences, these differences rarely translate to clinically significant outcomes for most patients with diabetes.