Pharmacokinetics

Loading Dose LD

TRYükleme Dozu
Also known as:Priming dose

An initial dose, or series of doses, larger than the maintenance dose, given to reach the target plasma concentration rapidly instead of waiting 4–5 half-lives for accumulation.

Formula

LD = Ctarget × Vd / F LD = (Ctarget − Ccurrent) × Vd / F

In depth

The loading dose depends on the volume of distribution, the target concentration (Ctarget) and bioavailability, and is independent of clearance; if drug is already present, it is based on the difference between Ctarget and the current concentration (Ccurrent). It is most useful when a prompt effect is required for drugs with long half-lives, such as amiodarone, digoxin, phenytoin and teicoplanin, and for vancomycin in serious infections.

For narrow-therapeutic-index drugs or those with slow distribution, the loading dose may be divided or infused slowly to avoid excessive early concentrations in the central compartment. Without a loading dose, steady-state concentrations are approached only after about 4–5 half-lives of maintenance dosing, which for amiodarone means months.

Clinical pearl

In renal impairment the loading dose is generally kept unchanged and only the maintenance dose is reduced; reducing the loading dose as well delays therapeutic concentrations, which matters for antimicrobials in sepsis.

Example drugs

Amiodarone Digoxin Phenytoin Vancomycin Teicoplanin
TRIn Turkish

Yükleme Dozu

Birikim için 4–5 yarılanma ömrü beklemek yerine hedef plazma konsantrasyonuna hızla ulaşmak amacıyla verilen, idame dozundan büyük başlangıç dozu veya doz dizisidir.

Yükleme dozu dağılım hacmine, hedef konsantrasyona (Ctarget) ve biyoyararlanıma bağlıdır, klirensten bağımsızdır; vücutta zaten ilaç varsa hedef konsantrasyon ile mevcut konsantrasyon (Ccurrent) arasındaki farka göre hesaplanır. En çok amiodaron, digoksin, fenitoin ve teikoplanin gibi yarılanma ömrü uzun olup etkinin hızla başlaması gereken ilaçlarda ve ciddi enfeksiyonlarda vankomisin tedavisinde yararlıdır.

Terapötik indeksi dar veya dağılımı yavaş ilaçlarda yükleme dozu, santral kompartmanda erken dönemde aşırı yüksek konsantrasyonları önlemek için bölünerek ya da yavaş infüzyonla verilebilir. Yükleme dozu verilmezse kararlı durum konsantrasyonlarına ancak idame dozlamasının yaklaşık 4–5 yarılanma ömrü sonunda yaklaşılır; bu süre amiodaron için aylar demektir.

Böbrek yetmezliğinde yükleme dozu genellikle değiştirilmez, yalnızca idame dozu azaltılır; yükleme dozunun da azaltılması terapötik konsantrasyonlara ulaşmayı geciktirir ve bu durum sepsiste antimikrobiyal tedavi açısından önem taşır.

Diğer adları:Doyurma dozu
Updated 24.09.2026 1 views Educational reference — verify against current sources before clinical use.

Read next

Maintenance Doseİdame Dozu

The dose given at regular intervals, or the rate of a continuous infusion, that replaces the amount of drug eliminated and keeps the concentration at the desired steady-state level.

 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.

 Steady-State ConcentrationKararlı Durum Konsantrasyonu

The constant plasma drug concentration achieved when the rate of drug administration equals the rate of elimination during repeated dosing.

 Elimination Half-LifeEliminasyon Yarı Ömrü

The time required for the plasma concentration of a drug to decrease by 50% during the elimination phase, reflecting how long the drug remains active in the body.

 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.

 Renal Dose AdjustmentBöbrek Fonksiyonuna Göre Doz Ayarlaması

The modification of the dose or dosing interval of a drug that is cleared, or has active or toxic metabolites cleared, by the kidneys, to prevent accumulation and toxicity in renal impairment.