Clinical DevelopmentLast reviewed April 2026

Pharmacokinetics(PK)

The study of how a drug moves through the body: absorption, distribution, metabolism, and excretion over time.

Usage Examples

The dose-ranging Phase 1 PK study established linear pharmacokinetics across the evaluated dose range.
Population PK modeling supported dosing recommendations in renal impairment and pediatric populations.

What is PK?

Pharmacokinetics (PK) characterizes what the body does to a drug — the time course of absorption, distribution, metabolism, and excretion (ADME). Standard PK parameters include Cmax (peak concentration), Tmax (time to peak), AUC (area under the curve / total exposure), clearance, volume of distribution, and half-life. These parameters drive dose selection, dosing interval, drug-drug interaction predictions, and special-population dosing adjustments.

PK data supports regulatory decisions throughout drug development: first-in-human dose selection, dose-proportionality assessment, food effect evaluation, renal and hepatic impairment dosing, DDI assessment, and bioequivalence. FDA Clinical Pharmacology reviewers evaluate PK data in every NDA and BLA; PK inadequacies are a common source of Complete Response Letters. Population PK modeling (pop-PK) integrates PK data with demographics to inform dosing in diverse populations.

Regulatory Context

This term appears most often in clinical development workflows where submission quality, regulatory evidence, and audit readiness depend on consistent language. It is commonly referenced alongside ICH E4, ICH E7, ICH M12.

FDAEMAPMDA

When This Matters

The dose-ranging Phase 1 PK study established linear pharmacokinetics across the evaluated dose range.
Population PK modeling supported dosing recommendations in renal impairment and pediatric populations.

Common Mistakes

Applying one-region clinical assumptions to global submission strategies.
Missing protocol-to-regulation traceability for pivotal studies.
Underestimating how regional guidance updates impact trial documentation.

Related Regulations

ICH E4ICH E7ICH M12FDA PK GUIDANCE

Frequently Asked Questions

Cmax, Tmax, AUC (total and per interval), clearance, volume of distribution, half-life, and accumulation ratio for multi-dose regimens. Special-population data (renal, hepatic, elderly, pediatric, drug interactions) are evaluated based on drug class and indication.

Population PK (pop-PK) models combine PK data across individuals to characterize typical parameters, inter-individual variability, and covariate effects (age, weight, renal function, etc.). Pop-PK supports dosing recommendations in subpopulations where dedicated studies weren't feasible.

Bioequivalence is demonstrated through PK parameter comparison — test and reference products must produce equivalent Cmax and AUC within 80-125% (or tighter bounds for NTI drugs). BE is a specific PK-based regulatory demonstration for generic and hybrid applications.