Also known as: Levemir · insulin detemir rDNA origin
| Parameter | Value | Source |
|---|---|---|
| Elimination Half-Life (SC) | ~5–7 hours (dose-dependent) | FDA NDA 021536[1] |
| Onset of Action | 1–2 hours | FDA NDA 021536[1] |
| Time to Peak (Tmax) | 6–8 hours | FDA NDA 021536[1] |
| Duration of Action | 16–24 hours (dose-dependent) | Plank J et al. 2005[2] |
| Bioavailability (SC) | ~60% | FDA NDA 021536[1] |
| Plasma Protein Binding | >98% (albumin) | FDA NDA 021536[1] |
| Time to Steady State | 2–3 days (once-daily dosing) | FDA NDA 021536[1] |
| Full Clearance (5 × t½) | ~25–35 hours (dose-dependent) | Calculated |
| Route of Administration | Subcutaneous injection only | — |
| Standard Dosing Frequency | Once or twice daily | FDA NDA 021536[1] |
| Data Quality | Human RCT — FDA NDA 021536; Plank J et al. Diabetes Care 2005 | |
Insulin detemir (Levemir) has a subcutaneous elimination half-life of approximately 5–7 hours, which is dose-dependent — larger doses result in half-lives at the longer end of this range.[1] Despite this relatively short plasma half-life, detemir achieves a duration of action of 16–24 hours, substantially longer than its t½ would predict. This extension is mediated by high-affinity albumin binding via the C14 fatty acid chain attached at the B29-lysine position of the insulin molecule.[2]
FDA approved Levemir (insulin detemir rDNA origin injection) under NDA 021536, first approved in June 2005. Detemir is approved for improving glycaemic control in adults and paediatric patients (≥2 years) with type 1 diabetes, and in adults with type 2 diabetes.[1]
The pharmacokinetics of insulin detemir were characterized in dedicated human PK studies using euglycaemic glucose clamp methodology — the gold standard for insulin PK assessment. In the glucose clamp, a constant IV glucose infusion is titrated to maintain euglycaemia, and the glucose infusion rate (GIR) serves as a proxy for insulin bioactivity over time. Plank et al. (2005) used this approach in a randomized crossover study comparing detemir, glargine, and NPH in 54 people with type 1 diabetes.[2]
The three-layer PK model is essential for insulin detemir:
The mismatch between plasma half-life and effect duration is not unique to detemir — it reflects the two-phase albumin binding that creates both an SC depot and a prolonged circulating reservoir. The C14 fatty acid chain enables detemir to bind albumin in plasma (~98% protein bound), which markedly slows renal filtration and proteolytic access, extending residence time in circulation despite the relatively short terminal half-life measured in plasma.[1]
After a single subcutaneous dose, insulin detemir declines from peak concentration according to the 5–7 hour half-life. Using the midpoint estimate of 6 hours:
| Half-Lives Elapsed | Time After Dose | % Remaining in Plasma | Clinical Note |
|---|---|---|---|
| 1 | ~6 hours | 50% | Approaching Tmax; peak effect zone |
| 2 | ~12 hours | 25% | Declining plasma level; still significant GIR |
| 3 | ~18 hours | 12.5% | Approaching end of clinical effect window |
| 4 | ~24 hours | 6.25% | Near end of 24-h dosing interval |
| 5 (clinical clearance) | ~30 hours | ~3% | Pharmacologically negligible plasma level |
After the first dose, detemir's glucose-lowering activity peaks at approximately 6–8 hours post-injection (Tmax) and declines progressively. Clinical blood-glucose-lowering effect is detectable for 16–24 hours in most patients. The dose-dependence of both t½ and duration means higher doses extend coverage — a clinical feature used in dose-titration strategies.[1]
With once-daily dosing, insulin detemir reaches steady state after approximately 2–3 days (3–5 doses). At steady state, trough concentrations are higher than after a single dose, and the 24-hour glucose-lowering profile becomes more consistent. Patients who initially require twice-daily dosing may achieve once-daily coverage once steady-state accumulation is established and dose titration is complete.[1]
The 16–24 hour duration of action supports once-daily dosing in many type 2 diabetes patients and in type 1 patients with lower basal insulin requirements. However, because the duration is dose-dependent and does not reliably reach 24 hours at lower doses, many type 1 diabetes patients use twice-daily detemir to ensure continuous basal coverage. This contrasts with glargine (20–24 hours at all doses) and degludec (>42 hours), which are designed for once-daily administration.[2]
If a detemir dose is missed, plasma levels decline by approximately 50% within 6 hours of the scheduled injection time. The shorter half-life means there is less carryover protection compared to glargine or degludec. Hyperglycaemia may become apparent within 12–18 hours of a missed dose, particularly in type 1 diabetes. Patients should not double-dose to compensate — consult prescriber guidance.[1]
| Compound | Half-Life (SC) | Duration of Action | Dosing Frequency | Approval Status |
|---|---|---|---|---|
| Insulin Detemir (Levemir) | ~5–7 h (dose-dep.) | 16–24 h | Once or twice daily | FDA-approved NDA 021536 |
| Insulin Glargine (Lantus/Toujeo) | ~12–18 h | ~20–24 h | Once daily | FDA-approved NDA 021081 |
| Insulin Degludec (Tresiba) | ~25 h | >42 h | Once daily (flexible) | FDA-approved NDA 203314 |
| NPH Insulin (Humulin N / Novolin N) | ~4–6 h | 12–18 h | Twice daily | FDA-approved |
| Route | Half-Life | Bioavailability | Tmax | Notes |
|---|---|---|---|---|
| Subcutaneous (abdomen, thigh, upper arm) | ~5–7 h | ~60% | 6–8 h | Only approved route; site rotation required |
| Intramuscular | No published data | No published data | No published data | Not approved; absorption unpredictable |
| Intravenous | No published data | 100% (definitional) | Minutes | Not appropriate for detemir; IV regular or rapid-acting insulin used instead |
Insulin detemir is a prescription medication and is not included in standard SAMHSA-5 workplace drug test panels or routine forensic toxicology screens. As a protein-based hormone analogue, it requires specialized immunoassay or mass spectrometry testing for detection.[1]
WADA prohibits insulin analogs for athletes in competition. Specialized doping control laboratories can detect insulin detemir in urine using LC-MS/MS for approximately 12–24 hours after the last dose. Therapeutic use exemptions (TUEs) are available for athletes with diabetes requiring insulin therapy. The detection window is considerably shorter than the clinical duration of action, as urinary excretion of intact detemir is limited by its high protein binding.[3]
Insulin detemir is a recombinant human insulin analogue in which the B30 threonine of native human insulin is deleted and a C14 fatty acid (myristic acid) is covalently attached via an amide bond at the epsilon-amino group of B29-lysine.[1] This structural modification creates two distinct pharmacokinetic prolongation mechanisms:
Mechanism 1 — Subcutaneous depot formation: At the SC injection site, detemir self-associates into dihexamers and hexamers stabilized by zinc coordination and fatty acid-fatty acid interactions. This SC depot absorbs slowly into the interstitial space and lymphatics over hours, flattening the absorption curve and extending the action duration relative to regular human insulin.[2]
Mechanism 2 — Albumin binding in plasma: Once absorbed into the circulation, detemir binds non-covalently to serum albumin via its C14 fatty acid chain with an affinity constant in the low micromolar range. Greater than 98% of circulating detemir is albumin-bound at any time. Only the unbound fraction (~<2%) can engage insulin receptors or be cleared by renal filtration and proteolysis. This bound-unbound equilibrium creates a circulating reservoir that buffers rapid concentration changes and extends the pharmacodynamic effect beyond what the plasma half-life alone would predict.[1]
Dose-dependence arises because higher doses saturate the SC depot binding capacity and shift the albumin binding equilibrium, resulting in a larger circulating reservoir and longer effective half-life within the 5–7 hour range. Both mechanisms are absent in regular human insulin, which has no fatty acid chain and no albumin binding, explaining its 4–6 minute plasma half-life IV and ~2 hour SC action.[2]
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