Taking Valtoval 500 Tablet if you have advanced HIV infection can increase the risk of developing Thrombotic Thrombocytopenic Purpura/Hemolytic Uremic Syndrome (TTP/HUS). In TTP/HUS, small blood clots form suddenly throughout the body, which can lead to death. If you experience bloody diarrhea, abdominal pain, vomiting, blood in urine, fits, and bleeding from the nose or mouth, you should stop Valtoval 500 Tablet and seek emergency medical support and advice.