ANYONE who has ever woken up in the morning to that tell-tale twinge in the corner of the mouth which heralds the on-set of cold sores knows how irritating they can be. Unsightly and uncomfortable, the worst thing about them is that they just keep coming back.

Cold sores are one of the commonest manifestations of the herpes virus. It is estimated that at least one person in five is a chronic sufferer, afflicted by them at regular intervals. Treatment should be easy. A few applications of Zovirax, an anti-viral developed by Wellcome, and they soon disappear.

Unfortunately, however, Zovirax is only available on prescription and few cold sore sufferers feel the problem is bad enough to merit a visit to the doctor. Even if they do, doctors may be reluctant to prescribe Zovirax, either because they feel the complaint is too minor to treat or because the cream is so expensive.

That could be about to change. Wellcome is seeking authorisation to sell Zovirax as a cold sore treatment over the counter in pharmacies. The application is currently being considered by the licensing authorities, so Wellcome was unwilling to discuss the application. But, if all goes well, it should soon be available at the local chemist.

Wellcome's application is motivated less by concern for cold sore sufferers than by its desire to maximise profits. The patent on Zovirax runs out in 1995. That means it will face competition from generic manufacturers, who have incurred none of the research and development costs suffered by Wellcome, so can sell their own versions much more cheaply.

Switching to selling over the counter is one of the strategies Wellcome is using to protect its revenue from Zovirax. It hopes to be able to build brand-loyalty among consumers, so enabling it to maintain sales when its patent runs out and competitors come in to the market.

It already has permission for the switch in Germany, where the patent runs out in 1994, and it is planning a major launch of the treatment in the autumn. Applications have been filed in most other European countries. Judging by the record of such switches, its chances of building a successful brand are good.

The first drugs to be switched in Britain were Nurofen, the painkiller manufactured by Boots, and Imodium or Arret, the anti-diarrhoeal from Janssen, which have both been available from pharmacies since 1983. And both are now among the market leaders. Research in the US shows that, of the 10 best-selling drugs launched in the over-the-counter market since 1975, nine were formerly available on prescription only.

Boots' transfer of Nurofen has parallels with Wellcome's strategy for Zovirax. Nurofen can be used to treat a variety of ailments, from headaches and period pains to osteo-arthritis and other serious conditions. But pharmacies can only sell it for minor, self-limiting conditions like headaches. Patients with more serious ailments still have to consult their doctors.

That is reflected in the different dosages. Doctors can prescribe up to 2,400mg a day, double the maximum permitted in the over-the-counter version. But, because few people go to the doctor for headaches and period pains, it also meant that launching Nurofen in pharmacies had little effect on prescription sales.

Zovirax is used for all forms of the herpes virus, from shingles and chicken pox to genital herpes. Last year, its world sales were pounds 471m and, analysts estimate, it contributed pounds 263m to trading profits. With patent expiry looming, it is vital that Wellcome does all it can to protect revenue and it is hoping that the over-the-counter launch will create a new market while having little impact on prescriptions for other conditions.

Selling direct to consumers is more expensive than selling through doctors. Drugs have to be advertised and promoted, although industry guidelines impose strict rules on how this is done, and companies cannot have special offers, for example. It also requires important decisions about pricing.

When Nurofen was launched over the counter, it was slightly more expensive than the prescription charge at that time, but its greater efficacy meant consumers were prepared to pay the price. Wellcome's current plan is to charge the same as the cost of the prescription to the NHS.

More and more companies are considering switching their drugs to pharmacies as patents run out - a practice which is likely to be encouraged as the Government tries to reduce its healthcare bills and to encourage us to take more responsibility for our own health.

SmithKline Beecham, for example, is considering launching its ulcer treatment, Tagamet, in the over-the-counter market, although initially only in the US.

Only a limited number of drugs are suitable for selling through pharmacies - heart drugs, cancer treatments and other drugs for conditions which need constant supervision by doctors would clearly be unacceptable. Companies also have to consider local attitudes. In the US, where genital herpes is common, Wellcome is seeking approval to sell Zovirax in pharmacies. British sufferers are, however, less likely to want to treat such conditions themselves.

Drugs have to meet strict conditions set by the Committee on Safety of Medicines before transfer will be permitted. They should have a good safety profile, generally established while being prescribed by doctors, and should not cause serious harm if the recommended dosages are exceeded. The CSM will also be concerned if the ailment treated could mask something more severe - stomach cancer, for example, has similar symptoms to an ulcer.

The EC is attempting to harmonise drug classification and has recently issued a draft directive stipulating what should only be available on prescription. These include drugs which have to be injected (unless, like diabetes, the treatment is long-term and has to involve the patient),drugs where there is the risk of masking more serious conditions, or drugs where prolonged use could cause complications, severe side- effects, or be addictive. The implication of the directive, however, is that anything which does not meet the criteria should not be prescription-only.

The Proprietary Association of Great Britain (PAGB) represents manufacturers of non-prescription medicines and is keen to see the range of over-the-counter treatments expanded. But it is critical of the time taken by the CSM to approve the switch - generally two to five years - even when it recommends the change.

A working party, established by the Medicines Control Agency, with representatives from the PAGB and the Association of the British Pharmaceutical Industry, is looking at of switching with the aim of establishing procedure and cutting the time required.

Self-medication is becoming more acceptable. Research commissioned by the Propriety Association found that the proportion of consumers prepared to treat themselves rose from 57 per cent in 1986 to 74 per cent in 1989. The more drugs available over the counter, the higher that figure is likely to get.

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