A patient with type 1 diabetes uses insulin glargine as basal insulin. Which pharmacokinetic property gives insulin glargine its 'peakless' 24-hour duration of action?

• A Extensive protein binding delaying absorption from the subcutaneous depot
• B Addition of zinc and protamine to delay systemic absorption
• C Long elimination half-life due to reduced renal clearance
• D Precipitation at physiological pH forming a microprecipitate that dissolves slowly ✓

Explanation

Insulin glargine is formulated at pH 4 as a soluble solution. After subcutaneous injection, the pH rises to physiological ~7.4, causing glargine to precipitate into isoelectric microcrystals at the injection site. These slowly dissolve over 24 hours releasing small, consistent amounts of insulin monomers into the bloodstream — producing a flat, peakless pharmacokinetic profile that mimics basal insulin secretion. Zinc and protamine delay absorption in NPH insulin (isophane). Protein binding is not the primary mechanism for glargine.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.