Pharmacokinetics

Absorption

TRAbsorpsiyon
Also known as:Uptake · drug absorption

The process by which a drug enters the bloodstream from the site of administration, such as the gastrointestinal tract, skin, or lungs.

In depth

Most drugs are absorbed by passive diffusion of the un-ionised, lipid-soluble form down a concentration gradient; others rely on carrier-mediated uptake, and efflux transporters such as P-glycoprotein can limit absorption. Rate and extent depend on drug factors (solubility, lipophilicity, pKa, molecular size, formulation) and patient factors (gastric emptying, intestinal transit, splanchnic blood flow, absorptive surface area, food).

The rate of absorption is described by the absorption rate constant (ka) and reflected in Cmax and Tmax, whereas the extent is expressed as bioavailability (F) and AUC. Because of its very large surface area, the small intestine is the main site of oral absorption, even for weak acids.

Clinical pearl

Slowed gastric emptying (e.g. with opioids, anticholinergics or food) usually delays absorption and lowers Cmax without necessarily reducing the total amount absorbed; intravenous administration bypasses absorption altogether.

TRIn Turkish

Absorpsiyon

İlacın uygulama yerinden (örneğin gastrointestinal sistem, deri veya akciğerlerden) kan dolaşımına giriş süreci.

İlaçların çoğu, iyonize olmamış ve lipitte çözünen formlarının konsantrasyon gradyanı yönünde pasif difüzyonuyla absorbe edilir; bazıları taşıyıcı aracılı alım kullanır, P-glikoprotein gibi efluks taşıyıcıları ise absorpsiyonu sınırlayabilir. Absorpsiyonun hızı ve derecesi ilaca (çözünürlük, lipofilisite, pKa, molekül büyüklüğü, formülasyon) ve hastaya (mide boşalması, bağırsak geçiş süresi, splanknik kan akımı, emilim yüzey alanı, besin) bağlıdır.

Absorpsiyon hızı absorpsiyon hız sabitiyle (ka) tanımlanır ve Cmax ile Tmax'a yansır; absorpsiyonun derecesi ise biyoyararlanım (F) ve AUC ile ifade edilir. İnce bağırsak, çok geniş yüzey alanı nedeniyle zayıf asitler için bile oral absorpsiyonun başlıca yeridir.

Mide boşalmasının yavaşlaması (örneğin opioidler, antikolinerjikler veya besinle) genellikle absorpsiyonu geciktirir ve Cmax'ı düşürür, ancak emilen toplam miktarı her zaman azaltmaz; intravenöz uygulamada absorpsiyon basamağı tümüyle atlanır.

Diğer adları:Emilim · ilaç absorpsiyonu
Updated 24.09.2026 22 views Educational reference — verify against current sources before clinical use.

Read next

Absorption Rate ConstantAbsorpsiyon Hız Sabiti

A first-order rate constant (Ka) that describes the rate at which a drug is absorbed from the site of administration into the systemic circulation.

 BioavailabilityBiyoyararlanım

The fraction of an administered dose that reaches the systemic circulation unchanged, and the rate at which it does so; by definition, bioavailability is 1 (100%) for an intravenous dose.

 First-Pass Effectİlk Geçiş Etkisi

The metabolism of a drug in the liver (or gut wall) before it reaches systemic circulation, often reducing the bioavailability of orally administered drugs.

 Time to Maximum ConcentrationMaksimum Konsantrasyona Ulaşma Süresi

The time after dosing at which the maximum plasma concentration (Cmax) is observed; an index of the rate of drug absorption.

 Route of AdministrationUygulama Yolu

The path by which a drug is brought into contact with the body, such as oral, sublingual, rectal, intravenous, intramuscular, subcutaneous, inhaled, topical or transdermal.

 P-glycoproteinP-glikoprotein

An ATP-dependent efflux transporter (ABCB1, MDR1) that pumps a wide range of drugs out of cells, limiting their intestinal absorption and brain entry and promoting their biliary and renal excretion.