Läkemedelsclearance

Läkemedelsclearance refers to the process by which a drug is removed from the body, encompassing all pathways of elimination such as metabolic transformation in the liver, excretion by the kidneys, bile secretion, and pulmonary release. In clinical pharmacology, clearance is expressed mathematically as the volume of plasma from which the drug is completely removed per unit time, and it is a key determinant of a drug’s half‑life and dosing regimen. Clearance is calculated from the steady‑state concentration–time profile using the equation CL = Dose/AreaUnder the Curve, and it can be partitioned into intrinsic clearance (the organ’s ability to metabolize the drug independently of blood flow) and total systemic clearance, which also includes the effects of blood flow.

Factors that influence clearance include age, sex, genetic polymorphisms of metabolizing enzymes, organ function (particularly hepatic and renal), drug interactions that induce or inhibit enzymes, and the presence of disease states such as liver cirrhosis or chronic kidney disease. Accurate estimation of clearance is essential for predicting drug exposure, avoiding toxicity, and customizing treatment for special populations. Regulatory agencies require clearances to be characterized in pre‑marketing studies, and clinicians often adjust doses based on measured or estimated clearance in patients with impaired organ function. In Swedish clinical practice, pharmacokinetic guidelines commonly provide reference ranges for clearance values of many therapeutics, aiding in safe and effective prescription.