doserisposta

Dose-response, or dose–response relationship, describes how the magnitude of a biological or therapeutic effect varies with the dose or concentration of a drug or other agent. It is a fundamental concept in pharmacology and toxicology, linking exposure to effect across individuals and systems. In Italian pharmacology, the concept is usually referred to as curva dose-risposta or relazione dose-risposta.

Responses can be graded or quantal. A graded response plots effect against dose to produce a sigmoidal curve. Key parameters include Emax (maximum effect) and EC50 (the dose producing half-maximal effect). The Hill coefficient describes curve steepness and cooperativity. Potency refers to the dose needed for a given effect, while efficacy denotes the maximal achievable response. A drug may be highly potent but have limited efficacy, or vice versa. Partial agonists yield submaximal Emax.

Curve position and shape are influenced by receptor density, signaling efficiency, genetic factors, age, disease, and pharmacokinetics. Shifts to the left indicate increased potency; rightward shifts indicate reduced potency. Tolerance, tachyphylaxis, desensitization, and drug interactions can alter the dose–response profile. Quantal dose–response curves describe the proportion of individuals achieving a fixed effect at each dose and are used to assess safety and therapeutic index.

Mathematical models include the Hill equation, E = Emax · D^n / (EC50^n + D^n). Dose–response studies guide dose selection, compare drugs, and evaluate adverse effects, but have limitations when translating from models to clinical outcomes due to variability among individuals and conditions.