Pfizer's little blue pill, Viagra, loses patent protection in Ireland and Britain today. It is just the latest blockbuster drug to fall off the patent cliff – a multi-year window when some of the largest selling drugs of a generation come to the end of their period of exclusivity.

It's a feeling Pfizer knows only too well, having seen sales of Lipitor plummet 60 per cent last year.

Compared to the cholesterol drug – the world’s top selling prescription medication until the last couple of years – the impact of Viagra will be muted. Even with the dramatic slump in sales, Lipitor last year brought in more revenue than the erectile dysfunction therapy.

But it’s not insignificant. Viagra was the company’s sixth best-selling drug last year, pulling in income of $2.05 billion, up 4 per cent on 2011.

Pfizer is currently downplaying the importance of today's lapsed patent, comforted in large part by the fact that it has managed to extend patent protection in the all-important US market until 2020. It's clearly a long way from finished as a major revenue earner.

Competition
But in much of Europe, now including Britain and Ireland, the drug will face increased competition from generics. The most immediate impact for customers should be a fall in prices. Under Irish pricing agreements, drugs coming off patent face a cut of 50 per cent in the price they can charge.

From the company’s perspective, it anticipates the falloff in revenue might be less dramatic than for other drugs coming off patent. In the first place, by its nature Viagra has been a somewhat restricted product on the public healthcare market. That increased reliance on the private market in itself should ease the decline.

It is also the dominant brand in the sector and Pfizer hopes customers will stick with the branded product rather than take a chance with generic substitutes.

In any case, more than most patented drugs, Viagra is well used to competition. Even outside the legitimate alternatives – Cialis and Levitra – Viagra has long faced aggressive competition from counterfeit products selling online. A 2011 study by the company of product appearing on the 22 top ranking sites as Pfizer’s Viagra found that 80 per cent was not genuine. Many did have some of the drug’s active ingredient – sildenafil – but in much smaller amounts than Viagra.

That might provide some reassurance for staff at the company's plant in Ringaskiddy where much of the active pharmaceutical ingredient in Viagra is produced.

But there won't be any complacency. Workers at Pfizer's Irish businesses have seen significant cutbacks in recent years – especially following the $68 billion takeover of biotechnology group Wyeth in 2009. That acquisition was driven, in large part, by a need to counteract the increasing struggle of its in-house R&D teams to deliver the blockbuster drugs required to replace declining revenue from legacy products.

Since then, more than 1,000 employees have left the business in Ireland, some following a downsizing to prepare for the end of Lipitor’s protected status. Last year, there were job cuts at Ringaskiddy and this year more jobs are going as the firm announced the closure of a plant at Little Island, also in Cork. Competition from lower cost economies means ever increasing pressure on productivity.

But it’s not all without hope. When it announced its most recent job cuts, Pfizer did note that it was exploring the options for future investment in Irish plants.