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Microsomal Stability Assay


Metabolism stability refers to the susceptibility of drugs to bio-transformational enzymes such as CYPs and UGTs, which are abundant in the liver. Microsomes from liver are generally used to study in vitro drug metabolism. The metabolism of the drug in the body and whether it forms metabolites are also important parameters in assessing the bioavailability, toxicity, and dosing potential of a compound. Metabolic transformation of a drug taking place in liver can change significantly its efficacy, which may be harmful to the body. On this account, drug candidates are tested early in the discovery process for metabolic stability.

Microsomal stability assay

The metabolic stability assays offer a method to calculate the rate of clearance of a test compound over time in microsomal incubations, and these data are used to evaluate intrinsic clearance. Microsomal assays primarily assess metabolism by the cytochrome P450 system (phase I enzymes). Data from microsomal assays allow clients to identify metabolic properties earlier and focus on the improvement of drug candidates through structure-activity relationships. We provide microsomal stability assays for all small compounds such as pharmaceuticals, industrial chemicals, and clients’ products.

Microsomal Stability Assay Protocol

Test systemHuman liver microsomes (pooled)
Test Compound Concentration3 µM (or custom)
Microsome Concentration0.5 mg/mL
Time Points0, 5, 15, 30, 45, 60 minutes
Number of Replicates3
Negative ControlVehicle (0.1% DMSO)
Heat inactivated microsomes
Positive ControlsVerapamil (rapid clearance)
Diazepam (low clearance)
Compound Requirements50 µL of 10 mM solution

Creative Bioarray is committed to providing microsomal stability assay service with high effectivity and reliability to accelerate the drug development process. If you have any special needs or questions regarding our services, please feel free to contact us at or 1-631-626-9181. We look forward to working with you in the future.

Case Study

1. Preparation of rat liver microsomes

Rats were sacrificed, and liver was collected and perfused with saline. Liver homogenized using PBS. Liver was homogenized using PBS. The homogenate was centrifuged at 9000 x g for 20 min at 4 °C. Protein concentration was determined and stored at -80 °C until use.

2. Method Validation

As seen in the protocol above, dispense 30 µL of 1.5 µM test compound solution containing 0.5 mg/mL microsomes solution to the assay plates designated for different time points (0, 5, 15, 30, 45 min). After the incubation, transfer the supernatant from each well into a 96-well sample plate for LC/MS analysis.

  Test ArticleT1/2 (minute)CLint (mL/min/kg)Percent Remaining (%)
0 min5 min15 min30 min45 min

3. Data Analysis and criteria

  • CLint (uL/min/mg protein) = ln (2) * 1000 / t1/2 / protein conc.
  • Unit of Protein Conc. = mg/mL
  • T1/2 = 0.693/K

Note: K is the rate constant from a plot of ln [concentration] vs. incubation time.


  • High metabolism, T1/2 < 30 min;
  • Moderate metabolism, 30 min < T1/2 <120 min;
  • Low metabolism, T1/2 >120 min.

For research use only. Not for any other purpose.

Related Sections

ADME and Pharmacokinetic Services:

In Vitro Metabolism Services:

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Tel: 1-631-626-9181
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