[7] These enzymes are responsible for the hydrolysis of ester- and amide-bond-containing xenobiotics and drugs such as cocaine and heroin.

As part of phase II metabolism, the resulting carboxylates are then often conjugated by other enzymes to increase solubility and eventually excreted.

This enzyme is known to hydrolyze aromatic and aliphatic esters and can manage cellular cholesterol esterification levels.

It may also play a role in detoxification in the lung and/or protection of the central nervous system from ester or amide compounds.

[10][11][12][13] Genetic variants of CES1 can significantly affect both pharmacokinetics and pharmacodynamics of drugs metabolized by CES1, such as methylphenidate and clopidogrel.