Some things never seem to change. I spent much of the ten years during which I ran the Skin Care Campaign (SCC) explaining patiently to the government and to pharmacists that, where topical treatments for skin diseases are concerned, generic substitution can present serious problems. That was not only the view of the 35 patient organisations the SCC represents; it was strongly supported by dermatology nurse specialists, GPSIs in dermatology and consultant dermatologists.

At 83%, the UK already has one of the highest rates of generic prescribing in the Western world. In an attempt to cut the cost of medicines further, the Government is now consulting interested parties on its proposal to implement Automatic Generic Substitution (AGS) from January 2010. AGS requires pharmacists to dispense a cheaper “Generic Equivalent” product against a branded prescription, unless the prescriber has chosen (and remembered) to tick a special “opt-out” box. This could lead to a situation where a patient’s notes indicate that they are using Brand ‘X’ when the chemist has actually dispensed generic ‘Y’.

AGS poses a particular set of problems for people with skin diseases because the concept of “generic equivalent” assumes that only the active ingredients matter in defining a product. Where topical treatments are concerned, this assumption could scarcely be further from the truth. Here, formulations play a crucial role in determining pharmaco-kinetics, bio-availability, stability, potential for irritation or sensitivity, cosmetic acceptability and overall patient satisfaction and compliance. Examples abound where different formulations with the same concentrations of the same active ingredients behave entirely differently in clinical use in terms of efficacy and side-effects.

It is also well understood by those with a knowledge of dermatology that everyone’s skin behaves differently, often being sensitive to particular excipients. For this reason, the widest possible range of formulations is encouraged – not least by NICE in its guidance on, ‘The management of atopic eczema in children from birth up to the age of 12 years’, which recommend that, “Healthcare professionals should offer children with atopic eczema a choice of unperfumed emollients to use every day for moisturising, washing and bathing. This should be suited to the child’s needs and preferences, and may include a combination of products or one product for all purposes.” The guidance says also that, “Healthcare professionals should offer an alternative emollient if a particular emollient causes irritation or is not acceptable to a child with atopic eczema.”The obvious and incontrovertible implication of this is that, once found, the chosen emollient(s) should be both prescribed and dispensed.

The fact that MIMS publishes a table which lists potential skin sensitisers in emollients is another reflection of their clinical importance. Indeed, the problem of potential skin sensitisers is of such importance that MIMS also have a similar list for topical corticosteroids.

The commonest form of generic substitution in treatments for skin diseases is the replacement of a branded emollient with aqueous cream, which is very inexpensive but was developed as a put-on-and-rinse-off soap substitute, rather than as a put-on-and-leave-on emollient.

In their “Audit of adverse drug reactions to aqueous cream in children with atopic eczema,” Cork M J, Timmins J, Holden C, Carr J, Berry V, Young S, Ward SJ, Tazi-Ahnin, R., (Pharmaceutical Journal, 28 November 2003) reported on an audit of 100 children aged one to 16 years with atopic eczema, carried out in Sheffield in November 2002. it showed that an irritant reaction occurred in over 56 per cent of them when aqueous cream was used as an emollient as compared with only 17 per cent of children using all other emollients.

In a further article entitled ‘Skin Wars’ (Chemist & Druggist 24 July, 2004, p27), Dr Cork explained that it was the surfactant in the water phase that makes the difference – he called it differential partitioning. Aqueous cream is composed of emulsifying ointment 30% in purified water 70%. Sodium lauryl sulphate is present in the emulsifying wax within the emulsifying ointment formulation. However, there is no water in emulsifying ointment, so it does not cause the same problem with cutaneous reactions, despite being in a more concentrated form.

Because excipients vary so greatly, the only way that a particular topical formulation can be defined is by its brand name. With AGS, the patient is liable to be given different formulations on different occasions, leading to inconsistencies in treatment, often determined by the latest deal from competing generic suppliers, rather than by clinical experience and need. There is a real risk that this will cause patient confusion, especially amongst the elderly, and that it will reduce adherence to agreed treatment regimens. That, in turn, will lead both to poor clinical outcomes and  waste.

If the government insists on going ahead with the proposed scheme, responsibility for ensuring that patients get what they need will fall to doctors. It is important that they should understand the issues involved – and keep ticking the boxes.

Declaration of interests: The author is patient editor of the BMJ. He was chief executive of the Skin Care Campaign for ten years until March 2007, is an Honorary Member of the British Association of Dermatologists, an Honorary Member and chairman of Trustees of the Primary Care Dermatology Society, and chairman of the Oversight Committee for the All Party Parliamentary Group on Skin.