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N-acetyltranserase 2 gene mutations and bioavailability of isoniazid in tuberculosis patients

Abstract number: P1942

Zabost A., Augustynowicz-Kopec E., Brzezinska S., Kozinska M., Blachnio M., Zwolska Z.

Isoniazid (INH) is a most important drug used in the treatment of tuberculosis. INH is metabolised by N-acetyltransferase type 2 in the liver. The genetically polymorphic NAT2 is responsible for INH metabolism and bioavailability to the blood. Individuals can be classified as rapid or slow acetylators. The acetylation polymorphism is associated with an increased risk of drug toxicity and with and increased frequency of certain cancers. The objective of the study was associations between NAT2 genotyping and INH concentrations in fast and slow acetylators for personalised therapeutic dose.

Methods: Blood samples were taken from 22 patients before (time 0) and 1, 3, 6 hrs after drug administration. Plasma concentrations of INH were determined with biological and chromatography (HPLC) method. In both methods lowest measurable concentration was 0.2 mg /ml. This methods guarantee high accuracy and secured repeatable results. Genotyping: Genomic DNA was extracted by Blood DNA kit and amplified by PCR with two primers: NAT1 and NAT2. After amplification, the PCR product was cut separately with 3 different restriction enzymes: Kpn1, Tag1, and BamH1. A loss of a Kpn1 restriction site denotes NAT2*5 allele, a Tag1 restriction site denotes NAT2*6 allele, and a BamH1 restriction site denotes NAT2*7 allele. The products was separated on agarose gels. The presence of any 2 mutant alleles defines the slow-acetylator genotype, whereas the rapid acetylators have 1 or 2 wild-type NAT2*4 alleles.

Results: Four different NAT 2 alleles were detected in the tested population. There were 7 different NAT2 genotypes in 22 tuberculosis patients, including *4/*4, *4/*5, *4/*6, *4/*7, *5/*5, *5/*6, *6/*6. INH mean plasma concentration of 9 fast acetylators tested by both methods in 1 h were 2.7 (0.5–5) mg/ml whereas of 13 slow acetylator 4.5 (2–8) mg/ml. For all treated patients concentrations of INH and AUCtotal observed in the rapid acetylators were considerably lower then those found in the slow acetylators p < 0.05. The type of mutations in N-acetylotranserase gene were correlated with plasma concentration of INH.

Conclusion: On the basis of our results we suggest the using of NAT 2 genotyping for discrimination of the fast and slow acetylators in monitoring of tuberculosis therapy in one sample of the blood.

This work was supported by KBN nr. 2 PO5B 136 27

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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