Loprofin PKU Drink Loprofin PKU Drink is a low protein, low phenylalanine drink based on cows milk extracts designed for use as a milk substitute for the dietary management of conditions where it is necessary to restrict protein intake such as phenylketonuria, other inborn errors of metabolism & chronic renal failure. Loprofin PKU Drink is gluten free, wheat free, egg free & soya free.