Newer insulins — onset, duration and advantages

Classification by pharmacokinetics. Rapid-acting analogues (lispro, aspart, glulisine) — onset 10–20 min, peak 1–2 h, duration 3–5 h. Ultra-rapid (faster aspart, lispro-aabc) — onset ~5 min. Short-acting regular human insulin — onset 30–60 min, peak 2–4 h, duration 6–8 h. Intermediate NPH — onset 1–2 h, peak 4–8 h, duration 12–18 h. Long-acting analogues — glargine U100 and detemir, ~24 h and 12–20 h. Ultra-long-acting — glargine U300 and degludec, flat and peakless, lasting 24–42 h.

The core textbook point on basal insulins. The availability of various basal insulins with a shelf life of 24 hours or longer — including glargine, degludec, glargine U300 and detemir — has provided much-needed options to lower baseline glucose with a single daily injection, in addition to non-insulin agents. This simplification is the main gain for older patients.

Insulin carries a higher hypoglycaemia risk than most oral agents in older adults. The stated principle is to decrease that risk by carefully choosing an insulin preparation that matches the timing of hyperglycaemia, and by matching the complexity of the regimen to the patient's coping ability — not to the ideal physiological profile.

The pattern of hyperglycaemia differs with age. In older people, the relative contribution of basal hyperglycaemia is lower and that of postprandial hyperglycaemia higher than in younger patients. This argues for rapid-acting analogues at meals when a full regimen is feasible — but a basal-only regimen remains simpler and safer for most frail patients.

Advantages of analogues over human insulin in the elderly. Fewer nocturnal and severe hypoglycaemic episodes — degludec and glargine U300 have the flattest, most reproducible profiles and the lowest nocturnal hypoglycaemia; no need for exact 30-minute pre-meal timing with rapid analogues, which suits erratic eating and carer-dependent meals; and true once-daily dosing. For those unable or unwilling to manage a basal-bolus regimen, consider a twice-daily premixed analogue (analogues preferentially, to reduce hypoglycaemia).

Delivery devices. There appear to be no benefits on glycaemic control from using a pen, pump or vial-and-syringe in older populations. However, visual impairment and low dexterity due to arthritis may make vial and syringe impractical in the frail older adult. Pre-filled insulin pens are safe and effective for older adults, and in institutional care various patient, staff and cost factors make pen injectors the preferred mode of delivery.

Once-weekly basal insulin icodec (approved 2024 in the EU, Canada and Switzerland). In the ONWARDS 1–5 phase 3 programme in type 2 diabetes, icodec was non-inferior and in several trials superior to once-daily basal insulin for HbA1c reduction, while cutting basal injections from seven to one per week; a pooled analysis showed efficacy and hypoglycaemia profiles consistent across age subgroups. It was not recommended for type 1 diabetes because ONWARDS 6 showed higher rates of level 2 and level 3 hypoglycaemia versus degludec. Relevance to geriatrics: a once-weekly basal insulin is potentially transformative for the older adult with type 2 diabetes who depends on a family caregiver, a visiting nurse or a nursing home for injections — but note that steady state is not reached until 3–4 injections, a loading dose is used, and any hypoglycaemia is correspondingly prolonged and not rapidly reversible.