posology

Posology is the branch of pharmacology that deals with dosing of medicines. It concerns determining the amount of a drug to be administered, the route of administration, the dosing interval, and the duration of therapy, with adjustments made for individual patient factors.

Dose selection depends on drug properties such as pharmacokinetics and pharmacodynamics, including absorption, distribution, metabolism, elimination, and the drug’s therapeutic index.

Common elements include loading doses to rapidly achieve therapeutic levels, maintenance doses to sustain them, and titration to reach a target response. Dosing regimens account for body size (mg/kg, mg/m2), organ function, age (neonates, pediatrics, adults, elderly), and coexisting conditions.

Renal or hepatic impairment often necessitates dose reductions or longer intervals. Drug interactions, pregnancy, and lactation may also require adjustments.

In clinical practice posology is supported by product labeling, clinical guidelines, and, for some medicines, therapeutic drug monitoring. Individualized dosing may be informed by pharmacogenomics and dose-response modeling. The aim is to maximize therapeutic benefit while minimizing adverse effects.