Merck's Zocor, one of the biggest-selling drugs of all time, is set to lose up to 90% of its UK sales overnight following the introduction of generic competition.

Launched in the UK in 1989, Zocor (simvastatin) was the first drug in the cholesterol-lowering statin class of drugs, which now makes up the single biggest expense to the NHS and other healthcare systems.

The product earned £185 million in UK sales last year, with over 5.2 million prescriptions written in England in 2001, compared to 4.39 million for its closest rival, Pfizer's Lipitor.

Statins are one of the fastest growing class of medicines, with world-wide sales of around $19 billion. Last year Zocor ceded leadership of the statin market to Lipitor, which generated sales $8.6 billion.

Now generics manufacturer Alpharma has become the first to market its copy of simvastatin in the UK, but will shortly be joined by eight other companies eager to supply cut-price versions to meet the NHS's ever-growing demand for the drug.

The National Service Framework for Coronary Heart Disease has been a major driver of increased statin use, which has proven to be highly successful in reducing deaths through strokes and heart disease. The Government's heart czar Dr Roger Boyle estimated statins are responsible for saving between 4,000 and 6,000 lives every year.

The availability of generic versions may help curb NHS costs, with statins already representing the largest chunk of prescription costs, accounting for a fifth of last year's £850 million rise in NHS prescription costs.

But Government controls mean that Alpharma's list price at launch will remain the same as branded Zocor for several months, in order to give the NHS time to prepare for potentially huge cost savings.

Even for patients on Zocor, the switch to the generic version may not be completely straightforward, while GPs wishing to switch patients on other statins must carefully consider whether or not it is suitable for individual patients.

Alpharma's initial price will be 28 tablets for £18.03 at 10mg, and £29.69 for both 20mg and 40mg doses exactly the same as Zocor and Pfizer's Lipitor.

The costs associated with increasing statin use have prompted Dr Boyle to call for a NICE review into the class's cost-effectiveness.

The patent expiry has coincided with hints from the Department of Health that statins may soon be available to patients for purchase as over-the-counter medicines.

The move would be unprecedented in POM-P switches, but has been welcomed by many in the medical community

"This is a good option. It is a good way forward for expanding the prevention of coronary heart disease", Prof Chris Packard, Head of Clinical Biochemistry at Glasgow Royal Infirmary, told the Sunday Telegraph.

Merck Sharp and Dohme refused to comment on whether it would be applying for OTC status for Zocor.

Some concerns remain about the safety profile of statins, however, following the withdrawal of Bayer's Lipobay in 2001. Muscle wasting and other serious side-effects are seen occasionally in all statins, but simvastatin in particular has a wealth of data to show its overwhelmingly sound safety profile.

The newest statin, Crestor, was launched just a few months ago, with makers AstraZeneca claiming the drug is the most effective in lowering 'bad' LDL-cholesterol.

Given earlier fears over high-dose Crestor use, however, Zocor maintains the upper hand with its established safety profile. MSD is certain to push this with the recent UK launch of Ezetrol (ezetimibe) a cholesterol-absorption inhibitor co-marketed with Schering-Plough as a combination therapy with simvastatin.

Zocor is also open to generic competition in Germany, but its patent remains in force until 2005 in the US, where the majority of its sales are generated.

pharmafocus@pharmafile.co.uk