What is the difference between Novolog (insulin aspart) and Admelog (insulin lispro) in terms of efficacy and usage?

Novolog vs Admelog: Key Differences

Novolog (insulin aspart) and Admelog (insulin lispro) are both rapid-acting insulin analogs with essentially equivalent clinical efficacy, safety profiles, and pharmacokinetic properties—the primary difference is the specific amino acid substitution used to create each analog, but this translates to no clinically meaningful differences in glucose control or hypoglycemia rates in real-world practice. 1, 2, 3

Pharmacokinetic and Pharmacodynamic Properties

Both insulins function as rapid-acting analogs with nearly identical action profiles:

• Onset of action: Both begin working within 5 minutes (Novolog) to 15 minutes (Admelog) after subcutaneous injection 4, 5
• Peak effect: Both peak at 1-3 hours after administration 4, 2
• Duration of action: Both last 3-5 hours 4, 1
• Time to maximum glucose-lowering effect: Approximately 2 hours for both agents 1, 2

The molecular difference is that insulin lispro (Admelog) has proline and lysine reversed at positions B28 and B29, while insulin aspart (Novolog) substitutes aspartic acid at position B28 1, 2, 6

Clinical Efficacy

Direct comparison studies demonstrate no clinically significant differences in glycemic control between these two rapid-acting analogs:

• A randomized controlled trial comparing insulin aspart, insulin lispro, and buffered regular insulin in continuous subcutaneous insulin infusion showed equivalent HbA1c reductions across all three groups, with mean HbA1c changes of 0.00% for aspart versus 0.18% for lispro (not statistically significant) 3
• Both agents produce similar reductions in HbA1c when compared to regular human insulin in type 1 and type 2 diabetes 2, 6
• Hypoglycemia rates are comparable between the two analogs, with rates of 3.7 episodes per patient per month for aspart versus 4.4 for lispro in one comparative trial 3

Administration and Dosing

Both insulins follow identical dosing principles:

• Timing: Administer 15 minutes or less before meals for optimal postprandial glucose control 5, 6
• Initial mealtime dosing: Start with 4 units per meal or 0.1 units/kg per meal 5
• Delivery methods: Both available as U-100 vials and prefilled pens; Admelog also available in U-200 concentrated formulation 5, 1
• Pump compatibility: Both suitable for continuous subcutaneous insulin infusion with equivalent safety profiles 2, 3

Safety Considerations

The safety profiles are essentially interchangeable:

• Both carry similar risks of hypoglycemia and hypokalemia with overdosage 1, 2
• Pediatric use is established for both agents in children 3 years and older with type 1 diabetes 1, 2
• Both require dose adjustments in renal and hepatic impairment due to increased hypoglycemia risk 1, 2
• Nocturnal hypoglycemia rates are reduced compared to regular human insulin for both analogs 6

Cost and Formulary Considerations

The primary practical difference between these agents is cost and insurance formulary placement:

• Admelog was developed as a "follow-on" insulin lispro product and may be priced lower than branded alternatives in some markets 4
• Formulary exclusions and tier placement significantly impact patient out-of-pocket costs, often more than the actual clinical differences between products 4
• Patients on high-deductible plans or in the Medicare Part D coverage gap pay based on list price, making formulary status critical 4

Clinical Bottom Line

In clinical practice, choose between Novolog and Admelog based primarily on insurance formulary coverage and cost to the patient, not on perceived clinical superiority of one over the other. 4, 3 Both are appropriate first-line rapid-acting insulin analogs for type 1 and type 2 diabetes requiring prandial insulin coverage 4, 5

Common Pitfalls to Avoid

• Do not assume brand-name differences translate to clinical differences—these are functionally equivalent medications 3
• Patients must understand the rapid onset of both agents to avoid hypoglycemia from delayed meal consumption 4, 5
• Verify insurance coverage before prescribing—formulary restrictions may force switches that confuse patients unnecessarily 4
• When switching between these agents, no dose adjustment is typically needed due to equivalent potency 1, 2