Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Clinical Studies Chemotherapy 2011;57:7–11 DOI: 10.1159/000321045 Isoniazid Blood Levels in Patients with Pulmonary Tuberculosis at a Tuberculosis Referral Center Fanak Fahimi   a, b, d Farzad Kobarfard   e Payam Tabarsi   b Shabnam Hemmati   d Jamshid Salamzadeh   d Shadi Baniasadi   a, c a  Department of Pharmaceutical Care, b  Chronic Respiratory Disease Research Center and c  Virology Research Center, National Research Institute of Tuberculosis and Lung Diseases, Masih Daneshvari Hospital, and Departments of d  Clinical Pharmacy and e  Medicinal Chemistry, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran therapeutic drug monitoring may be needed to optimize INH dosage, especially in patients with inadequate clinical response or toxicity to INH. Copyright © 2010 S. Karger AG, Basel Introduction Around two billion of the world’s people, mostly those living in developing countries, are infected with Myco- bacterium tuberculosis [1]. Patients with drug-susceptible strains of tuberculosis (TB) have high cure rates and low toxicity with standard doses of the first-line medications [2]. However, treatment success of new sputum smear- positive TB cases in Iran was 83% in 2006 [3]. This rela- tively low cure rate may be related to low serum concen- trations of anti-TB drugs. A low serum drug level not only leads to treatment failure, but may also cause drug resistance, thus render- ing TB treatment more complex if only half of the multi- drug-resistant (MDR) TB patients would turn out to be smear negative [4]. In 2007, MDR-TB was found to be 48% in previously treated TB cases in Iran [3]. Although Ra- mazanzadeh et al. [5] reported that MDR-TB is much Key Words Isoniazid  Serum isoniazid  Therapeutic drug monitoring  Tuberculosis Abstract Background: Serum concentrations of isoniazid (INH) were evaluated in Iranian patients admitted to the Tuberculosis Ward of Masih Daneshvari Hospital, Tehran, Iran. Factors correlated to plasma INH levels were determined. Meth - ods: Blood samples were obtained 2 h after ingestion of 5 mg/kg INH in 82 patients (1 sample/patient) on days 3–15 of treatment. The following variables were investigated: INH plasma level, duration of therapy, age, sex, weight, dose of INH administered and smoking status. Results: The average ( 8SD) age and weight of patients were 60.68 8 18.53 years and 74.96 8 7.15 kg, respectively. INH concentrations were low in 14.63% and high in 23.17% of the patients (INH refer- ence range: 3–5 g/ml). Plasma INH was statistically corre- lated with duration of INH administration (Kendall’s rank cor- relation, r = 0.66, p ! 0.001) but not with other variables. Con- clusion: Based on the result of this study, plasma INH concentrations were not within the therapeutic range for 37.80% of the patients on conventional therapy. Therefore Received: February 11, 2010 Accepted after revision: September 9, 2010 Published online: December 3, 2010 Shadi Baniasadi, PhD Department of Pharmaceutical Care, Virology Research Center, NRITLD Masih Daneshvari Hospital Shahid Bahonar Avenue, Darabad, Tehran 19569 (Iran) Tel. +98 21 2610 9503, Fax +98 21 2610 9484, E-Mail baniasadi  @  nritld.ac.ir © 2010 S. Karger AG, Basel 0009–3157/11/0571–0007$38.00/0 Accessible online at: www.karger.com/che