Adverse Reactions & Pharmacovigilance

Side Effect

TRYan Etki
Also known as:Side-effect

An unintended effect of a medicine, occurring at normal doses, that arises from its pharmacological properties and may be harmful, neutral or occasionally beneficial.

In depth

Side effects usually reflect actions of the drug at its main target in other tissues or at secondary targets, such as the sedation caused by first-generation H1 antihistamines or the dry mouth caused by antimuscarinic agents. Because the term does not necessarily imply harm, it is not synonymous with adverse drug reaction, and a side effect may even be exploited therapeutically, as with the hair growth produced by minoxidil.

Regulatory texts now prefer the terms adverse reaction or undesirable effect: section 4.8 of the SmPC (Kısa Ürün Bilgisi, KÜB) is titled undesirable effects, whereas the patient leaflet (Kullanma Talimatı, KT) uses the more familiar term side effects.

Clinical pearl

Warning patients in advance about expected, benign effects (e.g., orange-red discolouration of urine and tears with rifampicin) prevents alarm and unnecessary discontinuation.

Example drugs

Diphenhydramine Minoxidil Rifampicin Atropine
TRIn Turkish

Yan Etki

Bir ilacın olağan dozlarda ortaya çıkan, farmakolojik özelliklerinden kaynaklanan ve zararlı, nötr ya da bazen yararlı olabilen amaçlanmayan etkisidir.

Yan etkiler genellikle ilacın ana hedefi üzerinden başka dokularda ya da ikincil hedeflerde oluşturduğu etkileri yansıtır; birinci kuşak H1 antihistaminiklerin sedasyon yapması veya antimuskarinik ilaçların ağız kuruluğuna yol açması buna örnektir. Terim zarar anlamı taşımak zorunda olmadığından advers ilaç reaksiyonuyla eş anlamlı değildir; hatta minoksidilin saç büyümesini artırıcı etkisinde olduğu gibi bir yan etkiden tedavi amacıyla yararlanılabilir.

Düzenleyici metinler günümüzde advers reaksiyon veya istenmeyen etki terimlerini tercih eder: Kısa Ürün Bilgisi'nin (KÜB) 4.8 numaralı bölümü istenmeyen etkiler başlığını taşırken hastaya yönelik Kullanma Talimatı (KT) daha tanıdık olan yan etki terimini kullanır.

Beklenen ve zararsız etkiler konusunda hastanın önceden bilgilendirilmesi (ör. rifampisinle idrar ve gözyaşının turuncu-kırmızı renk alması) gereksiz endişeyi ve tedavinin gereksiz yere bırakılmasını önler.

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

Read next

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.

 Adverse EventAdvers Olay

Any untoward medical occurrence in a patient or clinical-trial subject given a medicinal product, whether or not it is considered causally related to the treatment.

 Type A Adverse ReactionTip A Advers Reaksiyon

An adverse drug reaction resulting from an exaggeration of a drug's known pharmacological action; it is dose-related, predictable and usually common but rarely fatal.

 SelectivitySeçicilik

The degree to which a drug acts on a particular target (receptor subtype, enzyme or tissue) rather than on others, usually expressed as the ratio of its affinities or potencies at different targets.

 Medication AdherenceTedaviye Uyum

The extent to which a patient's medication-taking behaviour corresponds with the recommendations agreed with the prescriber.

 Nocebo EffectNosebo Etkisi

The occurrence or worsening of symptoms, including adverse effects, that results from negative expectations about a treatment rather than from its pharmacological action.