Fosbait 500 Tablet is used to treat hyperphosphatemia (high phosphorus level in blood). It contains Lanthanum, which works by binding to the phosphate in the gastrointestinal tract and decreasing its absorption. In some cases, this medicine may cause side effects such as vomiting, upper abdominal pain, nausea, diarrhoea, stomach ache, indigestion, and flatulence. Inform the doctor if you are pregnant or breastfeeding, taking any other medication, or have any pre-existing medical conditions.