Montelukast is about 64% bioavailable, is cleared by CYP2C9 and CYP3A4 in the liver, and is nearly completely excreted into the bile. The physical properties of montelukast suggest that the drug undergoes transport by solute carrier transporters (SLC family transporters) and/or ATP-binding cassette transporters (ABC family transporters). Recent studies support the idea that genetic variation in genes encoding SLC and ABC transporters can influence the pharmacokinetics of drugs that are substrates for these transporters.