Lantus (Insulin Glargine)

Insulin Glargine (brand name Lantus) is a long-acting insulin analogue developed as a basal insulin. Basal means it covers the meal-independent baseline requirement, not the spikes after eating. That is exactly what separates it from rapid-acting insulins like aspart or lispro, which are tailored to the postprandial glucose rise.

Two changes are built in compared to human insulin: glycine instead of asparagine at position A21, and two extra arginine residues at the end of the B chain. The result is a molecule with a shifted isoelectric point - and the entire action profile follows from that.

This information is for research and educational purposes only. No medical advice.

The trick sits in the depot, not in the receptor. In the acidic solution inside the pen, glargine is clearly dissolved. The moment it lands in the neutral environment of subcutaneous tissue it precipitates as a fine microprecipitate. From that depot the active substance redissolves slowly and evenly, spread across roughly a day.

In tissue, glargine is processed at the end of the B chain, so what mainly circulates in blood is the active metabolite M1. At the insulin receptor the substance then acts like endogenous insulin: glucose moves into muscle and fat cells, the liver throttles its own glucose production, lipolysis is inhibited.

• Soluble at acidic pH: clear solution in the pen, no cloudiness, no resuspension needed.
• Precipitation at neutral pH: microprecipitate right after injection under the skin.
• Slow redissolution: even release without a peak.

In 2000, Lepore et al. compared glargine, NPH insulin, ultralente and continuous pump infusion under an isoglycemic 24-hour clamp. The picture was clear: NPH and ultralente showed a distinct peak effect after roughly 4.5 and 10 hours respectively, followed by waning. Glargine showed none at all. Onset came at around 1.5 hours, end of action at 22 hours versus 14 hours for NPH.

Hence the term peakless. In practice that means one administration per day, a flat baseline instead of a wave, and less dependence on the exact timing of meals.

What peakless does not mean is predictable. In 2004 Heise et al. measured day-to-day variability of the effect under clamp conditions: glargine was more even than NPH, but more variable than insulin detemir. A flat profile on average does not rule out deviations in the individual case.

In 2000, Ratner et al. treated 534 adults with type 1 diabetes for up to 28 weeks. Fasting values were lower under glargine, while at the same time fewer symptomatic hypoglycemic events occurred (39.9 versus 49.2 percent) and fewer nocturnal events (18.2 versus 27.1 percent) than under NPH.

In 2003, Riddle et al. reached practically identical HbA1c values with glargine and NPH in the Treat-to-Target trial across 756 people with type 2 diabetes. The difference lay elsewhere: roughly a quarter more participants reached the target without documented nocturnal hypoglycemia.

The largest data base comes from ORIGIN (NEJM 2012). 12,537 people with cardiovascular risk factors and dysglycemia were randomized for a median of 6.2 years to glargine or standard care. The cardiovascular result was neutral, and so was the cancer result - which largely defused the malignancy question debated at the time. The side effects clearly differed: severe hypoglycemia occurred more than three times as often under glargine (1.00 versus 0.31 per 100 person-years), and median weight rose by 1.6 kg instead of falling by 0.5 kg.

ORIGIN is therefore both at once: the best evidence for the long-term safety of the substance, and the best evidence that hypoglycemia is not a marginal phenomenon but the price of the main effect.

The risk does not come from unknown side effects but from the main effect. The substance lowers blood glucose reliably and dose-proportionally, it does not stop once a safe value is reached, and it does so across roughly 24 hours.

• Symptoms in order: tremor, sweating, palpitations, intense hunger, nervousness. Then impaired concentration, slurred speech, confusion, aggressive or slowed behavior. With a further drop: seizure, unconsciousness, death.
• No taking it back: the microprecipitate under the skin cannot be removed, neutralized or shortened. An excessive dose has to be sat out in full - under observation and with repeated carbohydrate intake. A single dose of sugar does not cover a 24-hour window.
• Fast carbohydrates within reach beforehand: glucose tablets, juice or sugared drinks belong on the table before administration, not in a cupboard. Fatty or protein-containing food acts too slowly.
• Never alone, never without measurement: without a blood glucose meter there is no objective feedback, and subjective impression is unreliable while the value is falling. Cognitive impairment sets in precisely when independent corrective action would be needed. Someone already confused generally cannot help themselves anymore.
• Especially critical at night: because a relevant part of the action window falls into sleep, the warning symptoms can be slept through.
• Alcohol and exertion: alcohol suppresses hepatic gluconeogenesis and thereby disables the body's own counter-regulation. Muscular work additionally increases insulin-independent glucose uptake.

With confusion or clouded consciousness, calling emergency services is the only correct response.

• Potassium shift: insulin transports potassium into cells. Serum values fall without any change in total body stores. Pronounced hypokalemia can trigger cardiac arrhythmias, and this risk is independent of blood glucose - carbohydrates alone do not correct it.
• Weight gain: a median of 1.6 kg over the study duration in ORIGIN.
• Risk of confusion: basal and mealtime insulin are both clear solutions in visually similar pens. Mixing them up is a documented medication error class, as is confusing U100 and U300.
• Local: injection site reactions, lipohypertrophy with repeated injection into the same region - making absorption unpredictable. Rotate injection sites.
• Other: sodium and water retention with edema, rarely allergic reactions.

Store unopened in the fridge at 2 to 8 degrees, do not freeze. Frozen insulin is unusable, even after thawing. Avoid direct sunlight and heat.

Pens in use are kept at room temperature and discarded after the in-use period stated by the manufacturer, regardless of remaining content. The solution is clear - cloudiness, discoloration or visible particles are an exclusion criterion. Keep out of reach of children.