Aug 19 (Reuters) - American Varvara Lepchenko has been provisionally suspended for an anti-doping rule violation after the 35-year-old returned a positive test for a prohibited substance, the International Tennis Federation (ITF) said on Thursday. Lepchenko provided a urine sample on July 12 during the Hungarian Grand Prix, which was found to contain metabolites of adrafinil and/or modafinil - both substances prohibited by the World Anti-Doping Agency, the ITF added. The world number 127 was issued a pre-charge notice on Aug. 9 and her provisional suspension came into effect on Thursday. "Lepchenko had (and retains) the right to apply to the chair of the independent tribunal convened to hear her case why the provisional suspension should not be imposed (or should be vacated), but has not exercised that right," the ITF said. Reporting by Shrivathsa Sridhar in Bengaluru Editing by Toby Davis Our Standards: The Thomson Reuters Trust Principles.