Insulin NPH
Intermediate-acting insulin with protamine suspension, providing 12-18 hours of basal coverage for twice-daily dosing.
Chemical Identity
| Property | Value |
|---|---|
| Chemical Formula | C257H383N65O77S6 (insulin component) |
| Molecular Weight | ~5808 Da (insulin) |
| CAS Number | 53027-39-7 |
| Peptide Class | Human Insulin with Protamine |
| Suspension | Isophane (NPH) |
Structure
NPH (Neutral Protamine Hagedorn) insulin is human insulin complexed with protamine, a basic protein from salmon sperm. The insulin-protamine complex forms crystals that dissolve slowly after subcutaneous injection. Each batch contains excess zinc to stabilize the suspension.
Mechanism of Action
NPH insulin crystals dissolve gradually in subcutaneous tissue, releasing insulin monomers that enter the bloodstream and activate insulin receptors. The slow dissolution provides intermediate duration of action (12-18 hours) but with more variability than long-acting analogs.
Clinical Applications
- Type 2 diabetes: Basal insulin, often combined with regular insulin
- Type 1 diabetes: Basal component in split-mixed regimens
- Cost-effective option: Less expensive than long-acting analogs
- Twice-daily dosing: Morning and evening injections
Pharmacokinetics
- Half-life: Variable (4-6 hours effective)
- Tmax: 4-12 hours (significant variability)
- Onset: 1-2 hours
- Duration: 12-18 hours
- Variability: Intra-individual CV 30-50%
Safety and Side Effects
Hypoglycemia (higher nocturnal risk than glargine due to pronounced peak), weight gain, injection site reactions, and variable absorption. Mixing with regular insulin reduces variability.
References
- Raskin, P., et al. (2002). Insulin glargine versus NPH insulin. Diabetes Care, 25, 346-350.
- Hirsch, I.B. (2005). Insulin analogues. New England Journal of Medicine, 352, 174-183.
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