Pharmacokinetics

Plasma Protein Binding PPB

TRPlazma Proteinlerine Bağlanma
Also known as:Protein binding · Drug–protein binding

The reversible binding of a drug to plasma proteins, chiefly albumin for acidic drugs and α1-acid glycoprotein for basic drugs, which determines the fraction of drug that is free to distribute and act.

In depth

Binding obeys the law of mass action and is expressed as the percentage bound or as the unbound fraction (fu). Only unbound drug crosses membranes, reaches receptors and is filtered at the glomerulus; bound drug acts as a circulating reservoir. Lipoproteins and specific globulins also bind some drugs and hormones.

Binding falls in hypoalbuminaemia (nephrotic syndrome, cirrhosis, critical illness), in uraemia and when a drug is displaced by other drugs, while α1-acid glycoprotein rises in inflammation and after surgery or trauma. Binding is usually measured by equilibrium dialysis or ultrafiltration.

Clinical pearl

Displacement interactions rarely matter clinically because extra free drug is rapidly cleared, but in hypoalbuminaemia a normal total phenytoin level can conceal a high free level; free phenytoin should be measured or a corrected level used.

Example drugs

Phenytoin Warfarin Valproic acid Lidocaine
TRIn Turkish

Plazma Proteinlerine Bağlanma

İlacın başta albümin (asidik ilaçlar) ve α1-asit glikoprotein (bazik ilaçlar) olmak üzere plazma proteinlerine geri dönüşümlü olarak bağlanmasıdır; dağılabilen ve etki gösterebilen serbest ilaç kesrini belirler.

Bağlanma kütle etkisi yasasına uyar ve bağlanma yüzdesi ya da serbest fraksiyon (fu) olarak ifade edilir. Yalnızca bağlanmamış ilaç membranları geçer, reseptörlere ulaşır ve glomerülde süzülür; bağlı ilaç dolaşımdaki bir depo işlevi görür. Bazı ilaç ve hormonlar lipoproteinlere ve özgül globulinlere de bağlanır.

Bağlanma; hipoalbüminemide (nefrotik sendrom, siroz, kritik hastalık), üremide ve ilaç başka ilaçlarca bağlanma yerinden ayrıldığında azalır; α1-asit glikoprotein ise inflamasyonda, cerrahi girişim veya travma sonrasında artar. Bağlanma genellikle denge diyalizi veya ultrafiltrasyonla ölçülür.

Artan serbest ilaç hızla temizlendiğinden bağlanma yerinden ayırma etkileşimleri nadiren klinik önem taşır; ancak hipoalbüminemide normal toplam fenitoin düzeyi yüksek serbest düzeyi gizleyebilir, bu nedenle serbest fenitoin ölçülmeli veya düzeltilmiş düzey kullanılmalıdır.

Diğer adları:Proteine bağlanma · Plazma proteinlerine bağlanma oranı
Updated 24.09.2026 1 views Educational reference — verify against current sources before clinical use.

Read next

Unbound FractionSerbest Fraksiyon

The proportion of the total plasma drug concentration that is not bound to plasma proteins, expressed as a fraction (0–1) or percentage; only this free drug can cross membranes and interact with receptors.

 Volume of DistributionSanal Dağılım Hacmi

A theoretical volume that describes the extent to which a drug is distributed throughout the body tissues relative to the plasma, indicating how much the drug leaves the bloodstream to enter tissues.

 Drug–Drug Interactionİlaç–İlaç Etkileşimi

A change in the magnitude or duration of a drug's effect, or in its concentrations, caused by the concurrent or prior administration of another drug.

 Therapeutic Drug MonitoringTerapötik İlaç İzlemi

The measurement of drug concentrations in blood at defined times, interpreted in the clinical context, to individualise dosing so as to maximise efficacy and minimise toxicity.

 DistributionDağılım

The reversible transfer of a drug from the bloodstream into the interstitial and intracellular fluids and tissues of the body after it has reached the systemic circulation.

 Renal ClearanceRenal Klirens

The component of total clearance attributable to the kidneys: the volume of plasma cleared of drug by urinary excretion per unit time.