After selecting the volunteers, Azithromycin drug manufactured by Dorsa Darou Company from Iran and Pfizer from Germany will be prescribed to them orally in two doses with an interval of 7 days. For example, if in the first period of the drug administration, the volunteer received the drug manufactured by Dorsa Darou, in the next turn, the volunteer will receive drug manufacturd by Pfizer company . Each time the amount of 6 cc of blood will be taken before drug administration and at times of 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 8, 12,24,48, 72 hour after the medication is prescribed. The next sampling will 7 days later. In the second time, similar to the first time of drug administration, blood sampling will be done. Finally, the amount of drug in each sample is determined by Lc Mass Mass equipment.