Drug Interactions

Synergism

TRSinerji
Also known as:Synergy · Synergistic interaction · Supra-additive effect

An interaction in which two drugs that each produce a given effect on their own cause a combined effect greater than that predicted from their individual effects under additivity.

Formula

a/A + b/B < 1 → synergy a/A + b/B = 1 → additivity a/A + b/B > 1 → antagonism (sub-additivity)

In depth

Synergy is judged against a reference model of additivity, most often Loewe additivity (isobolograms) or Bliss independence. In the Loewe interaction index, a and b are the doses used in combination and A and B the doses of each drug alone that produce the same effect; synergistic combinations fall below the line of additivity. Synergism differs from potentiation, in which one drug has no relevant effect of its own.

Synergy is exploited in antimicrobial combinations (a β-lactam plus an aminoglycoside against enterococci; trimethoprim plus sulfamethoxazole blocking sequential steps of folate synthesis) and in multimodal analgesia and anesthesia, but it also underlies dangerous combinations such as opioids with benzodiazepines.

Clinical pearl

Synergy can allow lower doses of each drug with fewer dose-related adverse effects, but the same principle makes combinations of CNS or respiratory depressants disproportionately dangerous.

Example drugs

Trimethoprim Sulfamethoxazole Ampicillin Gentamicin
TRIn Turkish

Sinerji

Her biri tek başına belirli bir etkiyi oluşturan iki ilacın birlikte, aditivite varsayımıyla tek başına etkilerinden beklenenden daha büyük bir etki oluşturduğu etkileşimdir.

Sinerji bir aditivite referans modeline göre değerlendirilir; en sık Loewe aditivitesi (izobologramlar) veya Bliss bağımsızlığı kullanılır. Loewe etkileşim indeksinde a ve b kombinasyonda kullanılan dozları, A ve B ise aynı etkiyi tek başına oluşturan dozları gösterir; sinerjik kombinasyonlar aditivite çizgisinin altında kalır. Sinerji, ilaçlardan birinin kendi başına ilgili bir etkisinin olmadığı potansiyalizasyondan farklıdır.

Sinerjiden antimikrobiyal kombinasyonlarda (enterokoklara karşı beta-laktam ile aminoglikozit; folat sentezinin ardışık basamaklarını bloke eden trimetoprim ile sülfametoksazol) ve multimodal analjezi ile anestezide yararlanılır; ancak opioidlerle benzodiazepinler gibi tehlikeli kombinasyonların temelinde de sinerji yatar.

Sinerji her bir ilacın daha düşük dozda kullanılmasına ve doza bağımlı advers etkilerin azalmasına olanak tanıyabilir; ancak aynı ilke SSS veya solunum depresanlarının kombinasyonlarını orantısız biçimde tehlikeli kılar.

Diğer adları:Sinerjizm · Sinerjistik etki · Supra-aditif etki
Updated 24.09.2026 0 views Educational reference — verify against current sources before clinical use.

Read next

Additive EffectAditif Etki

A combined effect of two drugs acting on the same endpoint that equals the effect predicted from their individual dose–response relationships, as if one drug were partly substituted for the other.

 PotentiationPotansiyalizasyon

An interaction in which a drug that lacks the relevant effect on its own increases the effect of another drug, through either a pharmacokinetic or a pharmacodynamic mechanism.

 Pharmacodynamic InteractionFarmakodinamik Etkileşim

An interaction in which one drug modifies the response to another at the same or related receptors, physiological systems or pathways, independently of any change in plasma concentrations.

 Dose–Response CurveDoz–Yanıt Eğrisi

A graph relating the dose or concentration of a drug to the magnitude of its effect (graded curve) or to the proportion of a population showing a specified all-or-none response (quantal curve).

 Physiological AntagonismFizyolojik Antagonizma

Opposition between two drugs that act on different receptors or pathways to produce opposing physiological effects, so that each counteracts the other's action.

 Ligand-Gated Ion ChannelLigand Kapılı İyon Kanalı

A transmembrane ion channel that opens (or, less often, closes) directly when a specific ligand, usually a neurotransmitter, binds to it, producing rapid changes in membrane potential within milliseconds.