A method of modulating plasma levels of branched chain amino acids and branched chain alpha-keto acids is disclosed, wherein an ammonia scavenger compound or a salt thereof, for example phenylbutyrate or an even numbered congener thereof or a salt thereof, is administered to an individual in need thereof. In various methods, a decrease in plasma levels of branched chain amino acids and branched chain alpha-keto acids is effected to treat individuals suffering from an inborn error in metabolism of amino acids, such as Maple Syrup Urine Disease, for example.
