Get to Know the ABCB1 Gene

What Is It?

ABCB1 (ATP-Binding Cassette subfamily B 1) aka Multi-Drug Resistance Protein 1 (MDRP1) codes for Pgp (Permeability glycoprotein) that pumps foreign substances out of the cells as a protective mechanism.

How does it affect your patients?

Variations in this gene can affect the absorption of many drugs. A good functional Pgp system decreases the efficacy of a drug where a patient might need an increase in dose


T/T allele:

  • Pgp system works efficiently
  • Drug absorption can be decreased

C/C allele

  • Pgp system is deficient
  • Drug absorption can be increased


A standard dose a medication may not be the same standard level of medication in the body due to Pgp system. Knowing how efficient or not the Pgp system works, can give insight if a dose may need to be decreased or increased due to rate of absorption.

Consider additive effects:

CYP2D6 PM + ABCB1 C/C Slowly metabolizing, rapidly absorbing. (Think of flooding your sink but not draining well) Concentration of a drug increases, therefore, a decrease in dose may be needed.