138RISK OF FAILURE AND TOXICITY OF ISONIAZID WITHOUT THERAPEUTIC DRUG MONITORINGIsoniazid (INH), a major antitubercular agent is subjected to an acetylating polymorphism. So Slow Acetylators risk an exaggerated accumulation of INH and Fast Acetylators are likely to see the drug become ineffective more quickly. The objective was to determine the risk of inefficiency and toxicity of INH from its acetylator phenotype. We carried out a prospective multicentric study in two pneumo-phthisiology Departments for 12 months. This study concerned patients presenting a first episode of pulmonary tuberculosis who have given their informed consent. Acetylator phenotype was determined by using Vivien method. We recruited 48 patients. The sex ratio and the mean age were similar in the groups. The serum level of isoniazid obtained at the third hour allowed to noting that only 25% of the patients were in the therapeutic zone and 75% were outside of therapeutic zone (15% in failure zone and 60% in the toxic zone). Among the Fast Acetylators, 19.3% (6/31) were in infratherapeutic zone and 41.9% (13/31) in toxic zone, while 94.1% of the Slow acetylators (16/17) were in toxic zone. The majority of patients in infratherapeutic zone (85.7%) was Very Fast Acetylators and received 5 mg/kg/d of INH. The comparison of the average doses according to the weight and recommended doses after measurement of the INH were respectively 5.58 against 7.09 mg/kg/d for Fast Acetylators and 5.29 against 2.12 mg/kg/d for Slow Acetylators. The unexpected event risk of AR/AL was of 2.02 (IC95% : 0.81-5.22). The determination of the acetylator phenotype of patients with tuberculosis permitted to specify the isoniazid dosage. The higher serum level makes run the risk of intolerance and the lower serum levels risk may be ineffective and allow consequently to the selection of resistant bacilli.kamadg@yahoo.frResearch812018Acetylator Phenotype,Isoniazid,Failure,Toxicity,Therapeutic Drug MonitoringMamadou Kamagate,Alimata Sandia Bakayoko-Yeo-Ténena, Kanga Sita N’zué,Boko Alexandre Kouassi,Augustine Kakou,Thérèse Daubrey-Potey,Zakaria Koné,Yaya Dao,Elisabeth Aka-Danguy,Kouao M Serge Domoua,Henri Die-KakouClinical Pharmacology Department, UFR-SMB, University Alassane Ouattara, Bouaké, Côte d’Ivoire.,Pneumo-phithisiology Department, UFRSMA, CHU Treichville, Cote d’Ivoire,Clinical Pharmacology Department, UFR-SMB, University Alassane Ouattara, Bouaké, Côte d’Ivoire.,Pneumo-phithisiology Department, UFRSMA, CHU Cocody, Cote d’Ivoire,Clinical Pharmacology Department, UFR-SMA, University Félix Houphouet-Boigny, Abidjan, Cote d’Ivoire.,Clinical Pharmacology Department, UFR-SMA, University Félix Houphouet-Boigny, Abidjan, Cote d’Ivoire.,Pneumo-phithisiology Department, UFRSMA, CHU Treichville, Cote d’Ivoire,Pneumo-phithisiology Department, UFRSMA, CHU Treichville, Cote d’Ivoire,Pneumo-phithisiology Department, UFRSMA, CHU Cocody, Cote d’Ivoire,Pneumo-phithisiology Department, UFRSMA, CHU Treichville, Cote d’Ivoire,Clinical Pharmacology Department, UFR-SMA, University Félix Houphouet-Boigny, Abidjan, Cote d’Ivoire.