Excretion and Mass Balance Studies
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Excretion and Mass Balance Studies

Before a drug can be approved for marketing and offered to patients, it must be extensively studied in nonclinical and clinical studies to demonstrate its safety and efficacy. Excretion and mass balance studies provided by BOC Sciences investigated the absorption and excretion of the drug after a single dose in subjects. The drug is radiolabeled to determine drug disposition and assess major metabolic pathways. Each study is tailored to the specific challenges unique to each project.

Introduction to Excretion and Mass Balance Studies

Mass balance studies are also known as absorption, distribution, metabolism and excretion (ADME) studies. Mass balance refers to collecting as much radiolabel as possible from human subjects in a clinical study. Radiolabeling is derived from excreta, including urine, feces, exhaled air, sweat, etc., while detecting exposure to radioactivity and drugs in whole blood, plasma, cerebrospinal fluid or other tissues of interest. The goal of excretion and mass balance clinical studies is to understand the excretion process of a drug after administration. Information on excretion and mass balance helps determine what additional clinical studies may be required for regulatory approval of a new drug.

Why Do Excretion and Mass Balance Studies

  • To study the balance of substances and compare the dose and recovery of radioactive administration
  • To study elimination pathways and the extent of absorption
  • To study metabolites in circulation and excreta
  • To study the clearance mechanism of drug
  • To study the exposure of prototypes and metabolites
  • To validate the rationality of animal species used for toxicological testing
  • To explore whether metabolites have an impact on pharmacological or toxicological effects

Excretion and Mass Balance Studies

Conduct Excretion and Mass Balance Studies with Us

We have many years of experience designing, conducting and interpreting excretion and mass balance studies. Our experienced staff has a deep understanding of pharmacokinetic data analysis and can provide our global clients with the following services:

  • Mass balance using radiolabeled test articles in rodents, dogs and non-human primates (NHP)
  • Determination of excretion kinetics in urine, feces, exhaled air and bile
  • Parent pharmacokinetics and total radioactivity (= total drug mass)
  • Research on the combination of mass balance and QWBA

Our Focus

  • Synthesis of radiolabeled active pharmaceutical ingredients

It can take up to one to two years for the drug to be radiolabeled. It is recommended to work with a radiochemist early in the development program and before clinical ADME studies are required. This requires the placement of a radioisotope (14C preferred) in the molecular fraction which can be used for the parent drug and all relevant metabolites

  • Quantitative whole body autoradiography studies

Quantitative whole-body autoradiography (QWBA) was used to determine dosimetric calculations of allowable radiolabel doses for ADME studies in humans. This study avoids the research risk of radiolabeled drugs accumulating in sensitive tissues and causing toxicity or damage.

  • Formulation development and good manufacturing practice

Proper planning around formulation development and production of adequate quantities of radiolabeled drug at the start of an R&D project.

  • Bioanalytical and pharmacokinetic (PK) parameters

Our qualified pharmacokineticists perform bioassays of drugs using validated bioanalytical methods to provide concentration data to determine PK parameters for parent drugs and metabolites.

  • Metabolic pathway analysis

Industry standards require the identification and characterization of metabolites that account for more than 10% of total measured drug and metabolite exposure (other health regulators outside the US have similar requirements). Understanding human metabolite characterization and metabolite structure identification (MetID) of drugs is critical.

  • Clinical pharmacology program

Develop a comprehensive clinical pharmacology plan to prepare your development program for the next step.

Features of Our Services

  • Expertise: Sampling of urine, feces, volatiles, cage washes, tissues, organs and remaining cadavers
  • Personalization: Standard or custom excretion and mass balance study services, tailored to the specific challenges unique to each project to meet our client's requirements
  • Comprehensive: Multiple routes of administration for multiple isotopes
  • Cost-effective: high quality and competitive price

Quotation and Ordering

As with all of our live services, we make sure to keep in touch during the study. If you have any special needs or questions about our services, please feel free to contact us to support our experienced experts. We look forward to working with you in the future.


  1. Quiroga P. Bioavailability: Mass Balance Studies. Springer, Cham. 2021.