Insulin Degludec
Metabolic / DiabetesAlso known as: Tresiba
Mechanism
The most stable basal insulin available — lasts over 42 hours with an incredibly flat profile. A fatty acid chain attached to the insulin molecule lets it form long chains under the skin and bind to albumin in the blood, creating a massive slow-release reservoir. This means you can inject it at different times each day without blood sugar swings. The DEVOTE trial proved it causes less severe hypoglycemia than other basal insulins.
Technical detail
Ultra-long-acting recombinant insulin analog produced in S. cerevisiae. Structure: des-B30 human insulin acylated at Lys-B29 with hexadecanedioic acid (C16 fatty diacid) via gamma-L-glutamic acid spacer. Multi-level depot mechanism: (1) at injection site, phenol/zinc-stabilized dihexamers self-associate into soluble multi-hexamer chains upon phenol diffusion post-injection, (2) zinc slowly dissociates → monomers released, (3) circulating monomers bind albumin (>99% bound) with slow dissociation. Result: half-life ~25 hours, duration of action >42 hours (vs. ~12h glargine half-life). This creates steady-state reservoir after 3-4 days of daily dosing, providing the flattest PK/PD profile of any basal insulin. Day-to-day variability 4x lower than glargine U100. DEVOTE trial (n=7,637): non-inferior HbA1c reduction vs. glargine with 40% lower rate of severe hypoglycemia (p<0.001 for superiority). Flexible dosing window: 8-40 hours between doses without efficacy loss.
Effects
METABOLIC SYSTEM: Insulin degludec is an ultra-long-acting basal insulin analog with a unique multi-hexamer depot mechanism [pharmacological]. STRUCTURAL MODIFICATION: The B30 threonine is deleted and a 16-carbon fatty diacid (hexadecanedioic acid) is attached to the B29 lysine via a glutamic acid spacer [crystallographic]. In the pharmaceutical formulation (with phenol and zinc), degludec exists as dihexamers. Upon subcutaneous injection, phenol diffuses away and the fatty diacid side chains create inter-hexamer associations, forming long multi-hexamer chains — soluble, stable depot structures at the injection site [pharmacokinetic, structural studies]. Zinc then slowly dissociates, releasing individual hexamers, which further dissociate to monomers that are absorbed into the bloodstream, where they bind albumin (via the fatty diacid chain) for further half-life extension [pharmacokinetic]. PHARMACOKINETICS: Half-life: >25 hours (longest of any basal insulin). Duration of action: >42 hours, with clinically meaningful glucose-lowering activity persisting beyond 48 hours [pharmacokinetic, clamp studies]. Time to steady state: 2-3 days. At steady state, the glucose-lowering effect is remarkably flat — coefficient of variation in glucose-lowering activity is 4x lower than insulin glargine U-100 (20% vs. 82%) [glucose clamp studies — Heise et al., 2012]. GLYCEMIC CONTROL: HbA1c reduction comparable to insulin glargine U-100 in type 1 and type 2 diabetes [RCT — BEGIN trials]. The primary advantage is not greater efficacy but rather: (1) lower rates of nocturnal hypoglycemia (26-36% reduction vs. glargine U-100) [RCT — BEGIN trials], and (2) dosing flexibility — can be administered at any time of day with a minimum of 8 hours between doses [RCT — BEGIN Flex]. CARDIOVASCULAR: DEVOTE trial (2017, Marso et al.) — landmark cardiovascular outcomes trial: insulin degludec was non-inferior to insulin glargine U-100 for MACE (major adverse cardiovascular events) in high-risk T2D patients. Significantly lower rates of severe hypoglycemia (27% reduction) in the degludec arm [RCT — DEVOTE]. COMBINATION: Available as Xultophy (degludec + liraglutide GLP-1 agonist) — basal insulin + incretin in a single daily injection, simplifying regimens [RCT].
Practitioner Guide
ADMINISTRATION: Subcutaneous injection once daily at any time of day — the ultra-long duration allows flexible timing. Use the same time daily when possible, but if needed, adjust timing with a minimum 8 hours between doses. Inject in thigh, abdomen, or upper arm. Rotate sites. DOSING — TYPE 2 DIABETES: Insulin-naive patients: start 10 units once daily (or 0.1-0.2 units/kg). Titrate by 2-4 units every 3-7 days targeting fasting glucose 80-130 mg/dL (ADA) or per provider preference. Switching from another basal insulin: unit-for-unit conversion from glargine U-100 or detemir (if once-daily). If switching from glargine U-300 (Toujeo): may need to increase degludec dose by ~10-15% (Toujeo doses tend to be higher due to its PK). DOSING — TYPE 1 DIABETES: Basal insulin typically 40-50% of total daily dose. Start at estimated basal need, titrate to fasting glucose target. Add mealtime rapid-acting insulin (aspart, lispro) for bolus coverage. FLEXIBLE DOSING ADVANTAGE: Degludec's 42h+ duration means that if a patient forgets their usual evening dose and remembers the next morning, they can inject then with minimal gap in coverage (unlike glargine U-100, where a delayed dose creates a clinically significant trough). This is a genuine real-world advantage for patients with irregular schedules — shift workers, travelers, adolescents. DEVOTE TRIAL IMPLICATIONS: Degludec demonstrated 27% less severe hypoglycemia than glargine U-100 at equivalent HbA1c — this makes degludec preferred for patients at high risk of severe hypoglycemia: elderly, hypoglycemia-unaware patients, patients with renal impairment, and those with cardiovascular disease. XULTOPHY (DEGLUDEC + LIRAGLUTIDE): 100 units degludec + 3.6 mg liraglutide per mL. Start at 16 dose steps (16 units degludec + 0.58 mg liraglutide). Titrate by 2 dose steps every 3-7 days. Max 50 dose steps daily. Elegant simplification for T2D patients needing both basal insulin and GLP-1 agonist. COST: Premium-priced (~$400-500/month without insurance). No biosimilar available yet (patent protection). Patient assistance programs available. STORAGE: Unopened: refrigerate (2-8°C). In-use: room temperature up to 30°C for 56 days (8 weeks — longer than glargine's 28 days, a practical advantage).
Research Summary
TIER 1: BEGIN trial program (7 Phase IIIa trials): demonstrated non-inferior HbA1c reduction vs. glargine U-100 in T1D and T2D with 26-36% reduction in nocturnal hypoglycemia. BEGIN Flex: dosing flexibility (extreme alternating 8h/40h intervals) achieved similar glycemic control to fixed-time dosing. DEVOTE trial (Marso et al., 2017 — NEJM): cardiovascular outcomes trial, 7,637 high-risk T2D patients, degludec non-inferior to glargine for MACE with 27% reduction in severe hypoglycemia. FDA-approved 2015 (Tresiba®). SWITCH 1 and 2 — crossover trials in T1D and T2D: degludec reduced overall and nocturnal hypoglycemia vs. glargine U-100 (double-blind, treat-to-target design). TIER 2: Glucose clamp studies characterizing the ultra-flat PK/PD profile (Heise et al., 2012 — 4x lower day-to-day variability vs. glargine). Systematic reviews and meta-analyses confirming hypoglycemia advantage (Ratner et al., 2013; Vora et al., 2014). Real-world evidence studies (EU-TREAT, CONFIRM) supporting trial findings in clinical practice. Cost-effectiveness analyses (favorable when hypoglycemia costs are included). Pharmacokinetic modeling of the multi-hexamer depot mechanism. TIER 3: Large registry analyses (Scandinavian diabetes registries). Pediatric use data (approved in T1D age ≥1 year). Special population data (elderly, renal impairment — no dose adjustment needed). Pump community discussions (degludec is not used in pumps — ultra-long action makes it unnecessary). KEY FINDINGS: Insulin degludec is the most pharmacokinetically advanced basal insulin — the ultra-flat, ultra-long profile translates into genuine clinical advantages (less hypoglycemia, flexible dosing) that matter for real-world patients. DEVOTE established cardiovascular safety. The multi-hexamer mechanism is an elegant piece of pharmaceutical engineering. Primary limitation is cost. GAPS: Head-to-head vs. glargine U-300 (both are ultra-long, but direct comparison limited to post-hoc analyses). Pediatric CVOT data lacking. Biosimilar timeline uncertain. ACTIVE TRIALS: Ongoing real-world evidence studies. Pediatric outcome studies. Xultophy in various T2D populations.