Precision Dosing and Therapeutic Drug Monitoring
Precision dosing and therapeutic drug monitoring (TDM) are the parts of clinical pharmacology that try to match the right amount of a drug to the right patient. They combine measured drug concentrations, pharmacokinetic and pharmacodynamic models, and increasingly a patient's genotype to move beyond fixed one-size dosing toward exposure that is tailored to the individual.
Definition
Precision dosing is the use of patient-specific information, including measured drug concentrations and genetic or physiological covariates, together with pharmacokinetic and pharmacodynamic models, to select or adjust a drug regimen so that exposure falls within a desired therapeutic range; therapeutic drug monitoring is the measurement of drug concentrations in body fluids to guide that adjustment.
Scope
This area orients the reader to the conceptual building blocks of individualized dosing: how genotype is translated into a predicted drug-handling phenotype, how dose-adjustment rules and algorithms are constructed, how population pharmacokinetic and pharmacodynamic models describe variability, how genotyping is combined with measured concentrations in TDM, and how Bayesian methods forecast an individual's exposure. It frames these as methods within pharmacogenomics and clinical pharmacology, not as drug-specific dosing instructions.
Sub-topics
Core questions
- How can a patient's genotype be converted into a predicted metabolizing or transport phenotype?
- What information (concentrations, covariates, genotype) most improves the prediction of an individual's drug exposure?
- How are population models built so that they capture and explain between-patient variability?
- When does adding genotyping to concentration-based monitoring change the predicted exposure?
- How can prior population knowledge and a patient's own measurements be combined to forecast future exposure?
Key concepts
- Therapeutic range and target exposure
- Pharmacokinetics and pharmacodynamics
- Predicted metabolizer phenotype
- Covariates of drug exposure
- Population variability
- Bayesian individualization
- Genotype-guided dosing
Key theories
- Population pharmacokinetic-pharmacodynamic modelling
- A framework in which fixed (typical) effects, covariate relationships, and random between- and within-subject variability are estimated simultaneously from sparse data across many individuals, providing the statistical backbone for individualized dosing.
- Model-informed individualization of dosing
- The idea that an explicit pharmacokinetic model, combined with computer estimation and a patient's own data, can adapt a dosing regimen to the individual rather than relying on fixed schedules.
Mechanisms
Individualized dosing draws on several layers of information. Genotype data are mapped to a predicted phenotype (for example, the predicted activity of a drug-metabolizing enzyme), which can shift expected drug exposure. Population pharmacokinetic-pharmacodynamic models, estimated from data across many patients, describe how typical parameters and identifiable covariates relate to exposure and how much unexplained variability remains. When a drug's concentration can be measured, therapeutic drug monitoring feeds those measurements back into the model. Bayesian forecasting then combines the population prior with the individual's measurements to estimate that person's parameters and project future concentrations, allowing the regimen to be refined.
Clinical relevance
Precision dosing and TDM are central to how variability in drug response is understood and studied in the health sciences, particularly for drugs with a narrow therapeutic range or large between-patient differences in handling. This area describes the methods by which exposure is characterized and individualized in research and practice; it is reference and educational material and is not a source of drug-specific dosing recommendations or individual treatment advice.
Evidence & guidelines
Implementation of pharmacogenomic and model-informed dosing is supported by consortium efforts that translate evidence into structured guidance, including the Clinical Pharmacogenetics Implementation Consortium and the Dutch Pharmacogenetics Working Group, whose guideline programs describe how genotype information can be acted upon. The statistical and modelling foundations were established earlier through population pharmacokinetic-pharmacodynamic methodology.
History
The field grew out of clinical pharmacokinetics in the 1970s, when Sheiner and colleagues proposed using explicit models and computer estimation to individualize dosing, and matured through the population pharmacokinetic-pharmacodynamic methods consolidated by the early 1990s. From the 2000s onward, the maturation of pharmacogenomics added genotype as a covariate, and implementation consortia began publishing structured guidance, bringing genetics into the established practice of therapeutic drug monitoring.
Key figures
- Lewis Sheiner
- Stuart Beal
- Mary Relling
- Teri Klein
- Jesse Swen
Related topics
Seminal works
- sheiner1972
- sheiner1992
- relling2011
Frequently asked questions
- How does precision dosing differ from therapeutic drug monitoring?
- Therapeutic drug monitoring is the measurement of drug concentrations to inform dosing decisions, while precision dosing is the broader goal of tailoring a regimen to the individual using those measurements together with models, covariates, and increasingly genotype.
- Where does genetics fit into individualized dosing?
- Genotype acts as one covariate among several: it can be translated into a predicted drug-handling phenotype that shifts expected exposure, which can then be combined with measured concentrations and population models.