LONDON, May 6 (Reuters) - Two rival cholesterol-lowering injections from Sanofi and Amgen have been recommended by Britain's healthcare cost watchdog after the manufacturers offered special discounts to the country's state-run health service.

Sanofi's Praluent, which was developed with Regeneron , and Amgen's Repatha are both so-called PCSK9 medicines that work in a different way to existing cholesterol fighters such as statins.

The National Institute for Health and Care Excellence (NICE) said in draft guidance on Friday that both drugs could be considered for use by people whose cholesterol is still not under control despite trying other treatments.

It stressed that the medicines would only be cost-effective with the promised discounts.

Both drugs cost more than 4,000 pounds ($5,780) per patient a year in Britain. That is already a lot less than their U.S. list price of around $14,000, but Sanofi and Amgen have committed to discount the British price by a further undisclosed amount for the UK National Health Service.

While Praluent and Repatha are both viewed by analysts as eventual multi-billion-dollar-a-year sellers, demand for the medicines in markets worldwide so far has proved disappointing.

($1 = 0.6921 pounds) (Reporting by Ben Hirschler; editing by Adrian Croft)