Toxicology

Toxicity

TRToksisite
Also known as:Toxic effect

The capacity of a substance to cause harmful effects in a living organism, or the harmful effect itself; it depends on dose, route, duration of exposure and the susceptibility of the exposed individual.

In depth

By time course, toxicity is classified as acute (single or short-term exposure), subchronic or chronic (prolonged repeated exposure), and by site as local or systemic, the latter including target-organ toxicities such as hepatotoxicity, nephrotoxicity, cardiotoxicity and ototoxicity. Mechanisms include exaggerated on-target pharmacology (e.g. bleeding with anticoagulants), off-target effects, reactive metabolites, immune-mediated injury and direct cellular damage.

For most medicines toxicity is dose- and concentration-dependent, which underpins the therapeutic index, therapeutic drug monitoring and dose adjustment in renal or hepatic impairment; idiosyncratic toxicity, in contrast, is largely unpredictable from dose. Effects may be reversible or irreversible, and some, such as carcinogenicity, appear long after exposure.

Clinical pearl

Drug toxicity often occurs without overdose: declining renal function, older age, dehydration or an interacting drug can raise concentrations of narrow-therapeutic-index drugs such as digoxin or lithium into the toxic range.

Example drugs

Digoxin lithium Gentamicin Methotrexate
TRIn Turkish

Toksisite

Bir maddenin canlı organizmada zararlı etki oluşturma kapasitesi ya da bu zararlı etkinin kendisidir; doza, uygulama yoluna, maruziyet süresine ve maruz kalan bireyin duyarlılığına bağlıdır.

Zaman seyrine göre toksisite akut (tek veya kısa süreli maruziyet), subkronik ya da kronik (uzun süreli tekrarlı maruziyet); yerleşimine göre ise lokal veya sistemik olarak sınıflandırılır. Sistemik toksisite hepatotoksisite, nefrotoksisite, kardiyotoksisite ve ototoksisite gibi hedef organ toksisitelerini içerir. Mekanizmalar arasında hedef üzerindeki farmakolojik etkinin aşırılaşması (ör. antikoagülanlarla kanama), hedef dışı etkiler, reaktif metabolitler, immün aracılı hasar ve doğrudan hücre hasarı yer alır.

Çoğu ilaçta toksisite doza ve konsantrasyona bağlıdır; terapötik indeks, terapötik ilaç izlemi ve böbrek ya da karaciğer yetmezliğinde doz ayarlaması bu ilkeye dayanır. İdiyosenkratik toksisite ise dozdan büyük ölçüde bağımsızdır ve öngörülemez. Etkiler geri dönüşlü veya geri dönüşsüz olabilir; karsinojenite gibi bazıları maruziyetten uzun süre sonra ortaya çıkar.

İlaç toksisitesi çoğu zaman doz aşımı olmadan gelişir: böbrek fonksiyonunun azalması, ileri yaş, dehidratasyon ya da etkileşen bir ilaç, digoksin veya lityum gibi dar terapötik indeksli ilaçların konsantrasyonlarını toksik aralığa yükseltebilir.

Diğer adları:Zehirlilik · Toksik etki
Updated 24.09.2026 1 views Educational reference — verify against current sources before clinical use.

Read next

ToxicologyToksikoloji

The science that studies the adverse effects of chemical, physical or biological agents on living organisms, including their mechanisms, detection, risk assessment and the management of poisoning.

 Adverse Drug ReactionAdvers İlaç Reaksiyonu

A noxious and unintended response to a medicinal product in which a causal relationship with the drug is at least a reasonable possibility.

 Therapeutic IndexTerapötik İndeks

A measure of a drug's relative safety, classically the ratio of the dose producing toxicity (TD50) or death (LD50) in 50% of subjects to the dose producing the desired effect in 50% (ED50).

 Narrow Therapeutic Index DrugDar Terapötik İndeksli İlaç

A drug for which small differences in dose or blood concentration may lead to serious therapeutic failure or serious adverse drug reactions.

 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.

 HepatotoxicityHepatotoksisite

Liver injury caused by a drug, herbal or dietary supplement or other chemical, ranging from asymptomatic aminotransferase elevation to cholestasis, hepatitis and acute liver failure.