In recent years generic sales have been booming but the competitiveness of the market has led to price wars, which in turn has seen growth slow.
This is particularly true in markets where generics are well established, such as the US and UK, which should see prices continue to fall in these nations.
Murray Aitken, senior vice president, Healthcare Insight, IMS, said: "The global generics market has posted double-digit gains in recent years. But in 2008, despite robust volume increases, we are seeing the first significant decline in sales growth as manufacturers increasingly compete in fierce price battles within most of the world's major markets.
"This trend is very apparent in markets like the US and UK as generics companies contend with aggressive competition and cost-containment measures enforced by both private and government payers."
US sales of generic drugs dipped by 2.7 per cent to $33bn in the year ending in September despite the volume of sales rising by 5.4 per cent.
This still represents the largest market for generics, accounting for 42 per cent of sales, but it appears growth will rely on new products coming off patent and other markets.
Fewer blockbusters came of patent in 2008 and consequently companies realised the largest growth in markets where generic penetration is lower. This was led by France, Italy, Spain and Japan, which all experienced double-digit growth.
Despite some difficulties for generic manufacturers in 2008 a bright future is predicted, with products generating sales of $139bn in established markets coming off patent between now and 2012.
In addition there is the new revenue stream offered by biogenerics, which should have a regulatory pathway approved in the foreseeable future.