Generic Name

Insulin Glargine

Brand Names

Lantus®, Toujeo®) is a recombinant, long‑acting basal insulin analogue engineered for a steady, 24‑hour glucose‑lowering profile. It is a cornerstone for both type 1 and type 2 diabetes management, particularly when basal coverage is required without pronounced peak activity.

Mechanism

• Reversible, non‑peptidic analogue of human insulin: Arg‑A21, Lys‑B31, Ser‑B32, Lys‑B33 substitution → altered isoelectric point and crystallization.
• Delayed absorption: Injected subcutaneously, insulin glargine precipitates in an acidic depot (pH 4.2) and slowly recrystallizes → continuous release.
• Binding to insulin receptors: Engages insulin receptor (IR) and activates downstream PI3K/Akt → glucose uptake, glycogen synthesis, lipogenesis, suppression of hepatic gluconeogenesis.
• Minimal peak effect (flat profile) → reduces hypoglycemia risk compared with first‑generation basal insulins.

Pharmacokinetics

Indications

• Type 1 Diabetes Mellitus (T1DM): Basal insulin replacement.
• Type 2 Diabetes Mellitus (T2DM): Basal insulin or combination with prandial insulins.
• Gestational Diabetes Mellitus: Basal‑prandial regimens in pregnancy.
• Other indications: Severe diabetic ketoacidosis when a basal component is required.

Contraindications

• Contraindications: Hypersensitivity to insulin glargine, insulin, or any excipient (e.g., metacresol, zinc).
• Warnings:
• Hypoglycemia: Particularly during the first week, at bedtime, or with variable diet/physical activity.
• Weight gain: Monitor BMI; lifestyle counseling essential.
• Cardiac/renal/hepatic impairment: Dose adjustments (Toujeo) and close monitoring required.
• Hypokalemia: Insulin shifts potassium into cells; caution in patients on potassium‑depleting medications.

Dosing

• Initiation: 0.2–0.4 U/kg/day (Lantus) or 0.4–0.5 U/kg/day (Toujeo) as basal component, usually at bedtime.
• Titration: 10 % increments every 3–4 days based on fasting capillary glucose.
• Maximum dose: 50 U/day for Lantus; 40 U/day for Toujeo (unless higher tolerated).
• Injection timing: Consistent time of day (evening or morning) for stable pharmacodynamics.
• Administration technique: 3–5 mm subcutaneous needle, rotate sites (abdomen, thighs, buttocks, upper arms); avoid intramuscular injection.
• Co‑administration: Can be combined with mealtime rapid‑acting insulin or analogues.

Adverse Effects

Monitoring

• Blood glucose: Pre‑breakfast, bedtime, post‑prandial (if mixed regimen).
• HbA1c: Every 3 months, sooner if titrating.
• Weight/BMI: Every visit; adjust diet/exercise.
• Renal/hepatic panels: Every 6–12 months (Toujeo dosing).
• Ketone bodies: During illness, pregnancy, or significant weight loss.
• Injection site assessment: Look for lipohypertrophy, abscesses.

Clinical Pearls

• Toujeo vs. Lantus: Toujeo’s ultra‑low concentration (300 U/mL) yields a flatter PK curve and allows lower daily doses, beneficial for patients with insulin resistance or higher weight.
• “First‑Day Hypoglycemia”: Most patients experience nocturnal lows the first week; counsel to check overnight glucose and adjust dose accordingly.
• Rotational injection sites: Skipping the upper arm and abdomen on consecutive days reduces lipohypertrophy and improves insulin absorption.
• Pregnancy: Use insulin glargine (dose‑adjusted) over basal‑bolus regimens when glycemia is stable; avoid abrupt changes in dose to minimize fetal risk.
• Titration schedule: A “rule of thumb” is to increase the basal dose by the same amount that was previously decreased if fasting glucose remains >80 mg/dL.
• Co‑administration with GLP‑1 RAs: Insulin glargine can be combined safely; GLP‑1s may offset weight gain.

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• Key pharmacology terms highlighted: insulin glargine, basal insulin, pharmacokinetics, hypoglycemia, weight gain, injection technique, dose titration, ADA guidelines.