Prescribing Guidance â€“ January 2011 Dietary Products for Phenylketonuria (PKU) Introduction Phenylketonuria (PKU) is an inherited metabolic disorder affecting the metabolism of foods containing protein. In people with PKU the enzyme required to convert the amino acid Phenylalanine into Tyrosine is either missing or its activity greatly reduced. PKU is diagnosed by screening at birth. If untreated, the build up of phenylalanine in the blood results in severe brain damage. PKU can be successfully treated by a low phenylalanine diet1.
Background In the financial year 2009-10 the total cost of prescribed low protein products was ÂŁ75,000 on low protein products alone. This does not include the cost of other products that people with PKU may need.
Who should they be prescribed for? People diagnosed as having PKU. These patients should be under the regular care of a specialist dietician. Whilst many of the low protein foods are gluten free, these products should be reserved for people with PKU or other metabolic disorders requiring a low protein diet as they are substantially more expensive than regular gluten-free products. The requirement for an ongoing low protein diet should be reviewed by a specialist dietician when patient reaches adulthood.
Which products should be prescribed? There are four elements to dietary prescribing for patients with PKU1-4: 1. 2. 3. 4.
A phenylalanine-free protein substitute (e.g. PKU Gel, PKU Abamix Infant etc.) Vitamins and minerals (if not contained in the substitute). Low protein foods which are ACBS listed (cereal, pasta, bread flour) Milk replacements (Calogen, Duocal, Loprofin Drink, Prozero and SnoPro) and glucose polymer supplements.
Low protein special foods are expected to provide 50% of estimated daily energy needs in patients with PKU. For this reason patients with PKU are likely to need a large quantity and variety of products on an ongoing basis. They are not readily available to purchase and all ACBS approved products (for PKU) are suitable for prescribing. Suggested quantities are outlined in the tables below:
Definition of PKU low protein prescribing â€˜unitâ€™3:
ACBS prescribeable foods
Definition of one unit
Pasta Bread/bread rolls Flour mix/cake mix Breakfast cereals Pasta snack pots Pizza bases Sausage/burger mixes Biscuits Energy supplements e.g. Duobar, Vitabite Cakes Egg replacer Dessert mixes Low protein spreads
1 box (500g) 1 packet 1 packet (500g) 1 packet 4 snack pots 2 pizza bases 4 sachets 1 packet (150g) 1 packet 6 x 40g 1 packet 6 sachets 1 tub
This table does not include milk replacements such as Calogen, Duocal, Loprofin Drink, Prozero and SnoPro and glucose polymer supplements. The quantity for prescription is determined on an individual basis.
Table indicating recommended maximum number of units of low protein foods for each age group3.
Age of patient with PKU 4 months -3 years 4-6 years 7-10 years 11-18 years Adults Pre-pregnancy/Pregnancy
Recommended maximum number of low protein items to prescribe each month 15 units 25 units 30 units 50 units 50 units 50 units
References 1. Phenylketonuria: Information for GPs about diet and PK. 2010. National Society for PKU 2. The patient with Phenylketinuria: Information for Pharmacists. National Society for PKU 3. The prescription of low protein foods in PKU. 2010. National Society for PKU 4. British National Formulary 60. September 2010. BMJ group and Pharmaceutical Press. www.bnf.org.uk Information on references (except BNF) available in Publications section of: The National Society for Phehylketonuria (United Kingdom) Ltd: www.nspku.org/ For more information please contact the Medicines Management Team on 01484 464276 /464281