en Immunology Immunology Original Research Original Research <p> <strong> Background: </strong>Cytochrome P450 2C19 (CYP2C19) is important in metabolism of wide range of drugs. <i>CYP2C19*17 </i>is a novel variant allele which increases gene transcription and therefore results in ultra-rapid metabolizer phenotype (URM). Distribution of this variant allele has not been well studied worldwide. The aim of present study was to investigate allele and genotype frequencies of <i>CYP2C19*17</i> in a healthy Iranian population and compare them with other ethnic groups. </p><p> <strong> Methods </strong>: One hundred eighty healthy unrelated Iranian volunteer took part in this study and were genotyped for <i>CYP2C19 *2, *3, *17</i> (-3402) by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and <i>CYP2C19*17 </i>(-806) by a nested-PCR assays. The distribution of <i>CYP2C19*17</i> polymorphism in Iranian population was then compared with other ethnic groups. </p><p> <strong> Results </strong>: The <i>CYP2C19*17</i> allele frequency was 21.6% in Iranian population. Among studied subjects 5.5% were homozygous for CYP2C19*17 and phenotyped as ultra-rapid metabolizers 28.8% were genotyped as <i>CYP2C19*1*17</i> (extensive metabolizers) and 3.3% as <i>CYP2C19*2*17</i> (intermediate metabolizers). </p><p> <strong> Conclusion </strong>: The <i>CYP2C19*17</i> genetic distribution in Iranian population is similar to Middle East or European countries. The high frequency of <i>CYP2C19*17</i> in Iranian population highlights the importance of this new variant allele in metabolism of CYP2C19 substrates. Thus, future association studies are required to reveal clinical consequence of this genetic polymorphism in carrier individuals. </p> CYP2C19, Genotyping, Iranian, Polymorphism, Polymerase chain reaction. 872 980 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-893&slc_lang=en&sid=1 Maryam Payan payan@razi.tums.ac.ir 200319475328460018696 200319475328460018696 No Biopharmaceutics and Pharmacokinetics Division, Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical sciences, Tehran, Iran. Nader Tajik nadertajik@yahoo.com, tajik.n@iums.ac.ir 200319475328460018697 200319475328460018697 Yes Immunology Research Center (IRC), Iran University of Medical Sciences, Tehran, Iran. Mohammad Reza Rouini rouini@tums.ac.ir 200319475328460018698 200319475328460018698 No Biopharmaceutics and Pharmacokinetics Division, Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Med-ical sciences, Tehran, Iran. Mohammad Hossein Ghahremani mhghahremani@razi.tums.ac.ir 200319475328460018699 200319475328460018699 No Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tehran University of Medical sciences, Tehran, Iran