Phlexy-Vits Powder Sachets Phlexy-Vits Powder is a concentrated powdered vitamin, mineral & trace element preparation. Phlexy-Vits may be used as the vitamin, mineral & trace element component of restrictive therapeutic diets & has been designed to meet the micronutrient requirements of older children (from Approx. 11 years) & adults. Phlexy-Vits can be used as part of the Phlexy-10 system for use in the management of phenylketonuria.