Genetic polymorphisms of drug-metabolizing enzymes and the susceptibility to antituberculosis drug-induced liver injury.

Three first-line antituberculosis drugs, isoniazid, rifampicin and pyrazinamide, may induce liver injury, especially isoniazid. This antituberculosis drug-induced liver injury ranges from a mild to severe form, and the associated mortality cases are not rare. The major drug-metabolizing enzyme of isoniazid is N-acetyltransferase. Other possible enzymes are CYP2E1 and glutathione S-transferase. There is evidence that polymorphisms of the genes that encode these enzymes may influence the activity of the corresponding drug-metabolizing enzymes. Recent studies demonstrated that these genetic polymorphisms may be associated with the susceptibility to antituberculosis drug-induced liver injury. The proposed risk-associated genotypes are NAT2 slow acetylator (without wild-type NAT2*4 allele), CYP2E1 *1A/*1A (homozygous wild type) and homozygous null GSTM1 genotype. Although the available data in the field are still limited and warrants further confirmation in different ethnic populations with larger sample sizes, it still cast some light on the application of these pharmacogenetic or pharmacogenomic approaches to prevent grave antituberculosis drug-induced liver injury in the near future.