USFDA Guidance: Pharmacokinetics in Patients with Impaired Hepatic Function: Study Design, Data Analysis, and Impact on Dosing and Labeling

Sharan Murugan
4 hours ago
4 min read

The U.S. Food and Drug Administration (FDA) has issued the September 2026 draft guidance “Pharmacokinetics in Patients with Impaired Hepatic Function: Study Design, Data Analysis, and Impact on Dosing and Labeling”. The guidance provides recommendations for sponsors and applicants planning studies to evaluate how hepatic impairment affects the pharmacokinetics (PK) and, where appropriate, pharmacodynamics (PD) of drugs, including therapeutic biological products. It is a draft, nonbinding guidance and is not for implementation.

Why Hepatic Impairment Matters in Drug Development

The liver plays an important role in drug elimination through metabolism and biliary excretion. Liver disease can alter drug-metabolizing enzymes, transporters, hepatic blood flow, and other processes that influence drug absorption, distribution, and elimination.

Because these changes can affect drug exposure and potentially safety or effectiveness, understanding the impact of hepatic impairment is an important part of drug development. The FDA guidance provides recommendations on when hepatic impairment studies may be appropriate, how they should be designed, how results should be analyzed, and how findings can inform dosage recommendations and labeling.

When a Dedicated Hepatic Impairment Study Should Be Conducted

FDA recommends a dedicated pharmacokinetic study in patients with hepatic impairment when hepatic metabolism or excretion accounts for more than 30% of elimination of the absorbed parent drug or active metabolites. A study is also recommended when small changes in drug concentrations could result in clinically meaningful differences in safety or effectiveness, when elimination pathways are not adequately characterized, or when the drug is intended to treat or is likely to be used in patients with hepatic impairment.

A dedicated study may not be warranted when hepatic impairment is unlikely to alter pharmacokinetics enough to require a different dosage. Examples include drugs with limited hepatic elimination, drugs eliminated entirely through the kidneys, single-administration products, locally acting drugs with limited systemic exposure, and certain gaseous or volatile drugs primarily eliminated through the lungs. FDA recommends assessing the effect of hepatic impairment early in development so that trial eligibility and dosage recommendations can be appropriately considered.

Assessing Hepatic Function

The guidance recommends selecting an appropriate method for classifying hepatic function according to the patient population.

For subjects with cirrhosis caused by chronic liver disease, FDA recommends the Child-Pugh (CP) classification. For patients with cancer, the National Cancer Institute (NCI) Organ Dysfunction Working Group criteria may be used, except in patients with hepatobiliary cancers where Child-Pugh classification may be more appropriate.

Child-Pugh classification categorizes hepatic impairment as mild, moderate, or severe, corresponding to CP groups A, B, and C. Other approaches may be considered when appropriate, but sponsors should consult the relevant FDA review division when proposing a different classification system.

Designing the Hepatic Impairment Study

The primary purpose of a dedicated hepatic impairment study is to determine how hepatic impairment affects drug pharmacokinetics and, where appropriate, pharmacodynamics, and whether the observed changes require different conditions of use, such as avoiding use, modifying the dosage, or increasing monitoring for adverse reactions.

Study subjects with hepatic impairment and normal hepatic function should be appropriately comparable for characteristics that may influence pharmacokinetics, such as age, sex, weight, and other relevant factors. Where pharmacokinetics are affected by polymorphic enzymes or transporters, genotype assessment may also be appropriate.

Sample size should be sufficient to provide precise estimates of relevant PK parameters, with justification for the selected number of subjects. A single-dose design is generally sufficient when the drug and active metabolites show dose-proportional and time-independent pharmacokinetics. A multiple-dose, preferably steady-state, design should be considered when pharmacokinetics are non-dose-proportional or time-dependent.

Sample Collection, Population PK, and Pharmacodynamic Assessments

Sampling should be adequate to characterize the pharmacokinetics of the parent drug and relevant active metabolites. For highly liver-extracted and extensively protein-bound drugs, FDA recommends particular attention to measuring unbound drug concentrations. Where applicable, PK parameters should be reported using both total and unbound concentrations.

A population pharmacokinetic (popPK) approach may be sufficient when clinical trials include adequate numbers of subjects with different degrees of hepatic impairment and sufficient concentration data are available. FDA recommends maintaining appropriate hepatic-function classifications, accurate dosing and sampling records, adequate samples, and relevant parent and active-metabolite measurements.

Pharmacodynamic assessments should be included when hepatic impairment could produce PD changes independent of PK changes. These assessments can be particularly useful when concentration-response information is unavailable or when hepatic impairment may alter the pharmacodynamic response.

Data Analysis and Development of Dosage Recommendations

PK data should be analyzed to estimate relevant parameters such as AUC, Cmax, clearance, volume of distribution, terminal half-life, Tmax, and fraction unbound. Sponsors should report appropriate measures of variability and compare total and unbound exposure between impaired and control groups, including associated confidence intervals.

Relationships between hepatic-function measures and PK parameters should also be explored using appropriate statistical models. These analyses can help identify predictors of changes in drug exposure and support refinement of dosage recommendations.

Dosage recommendations should be based on the overall relationship between hepatic function, drug exposure, and exposure-response relationships for efficacy and safety. If changes in exposure are not clinically meaningful, the same dosage used in patients with normal hepatic function may be appropriate. When a different dosage is needed, recommendations should generally be based on exposure matching to a reference group with an acceptable benefit-risk profile.

Labeling Recommendations

The prescribing information should include essential scientific information needed for the safe and effective use of the drug in patients with hepatic impairment, as appropriate.

Relevant information may include PK and PD findings, hepatic elimination of the drug and active metabolites, clinical effects associated with PK or PD changes, and recommendations for preventing, mitigating, monitoring, or managing risks. Where necessary, labeling may include different dosage or monitoring recommendations for patients with hepatic impairment.