posologia

Posologia, or posology, is the branch of pharmacology concerned with the study and determination of the appropriate amount and schedule of a drug's administration. It encompasses the science and practice of dosing regimens to achieve efficacy while minimizing adverse effects. Dosing regimens cover the amount per administration, the frequency of administration, the route of delivery, and the duration of treatment, including concepts such as loading doses, maintenance doses, titration, and on-demand dosing.

Dosing is influenced by pharmacokinetic and pharmacodynamic properties of the drug and by patient-specific factors. Key determinants include age, body weight or surface area, organ function (especially liver and kidneys), pregnancy and lactation status, genetic factors affecting metabolism, comorbidities, and potential drug interactions. The route and formulation (oral, intravenous, topical, sustained-release) also shape the posology.

Special populations require tailored dosing. Pediatric regimens are frequently based on weight or body surface area; elderly patients may have reduced clearance and sensitivity to medications; pregnancy-related considerations balance maternal benefit and fetal risk, with often adjusted dosages or alternatives.

Dosing information is derived from clinical trials, pharmacokinetic and pharmacodynamic data, and regulatory labeling, and is summarized in pharmacopoeias and clinical guidelines. Clinicians use standard units such as mass (mg, g) per dose, time intervals, and sometimes weight-based or area-based calculations (mg/kg, mg/m2). Monitoring, therapeutic drug monitoring when indicated, and adherence assessment are integral to ensure appropriate posology.

Safety considerations include avoiding underdose that risks inefficacy or overdosage that causes toxicity, recognizing interactions, and adjusting for organ impairment. Dosing errors remain a focus of pharmacovigilance and quality assurance.