Irish manufacturing output fell by 4.5 per cent between the second and third quarter of the year, according to the Central Statistics Office. On an annual basis, production was 13.7 per cent lower year-on-year in September, the largest annual decline since November 2009.

The decline was driven by the pharmaceutical sector, which recorded a 35.2 per cent monthly decline in basic pharmaceuticals and a 31.9 per cent fall in chemicals and pharmaceuticals, according to Davy Research.

In a note published yesterday, they described the decline as a "worrying development" that might represent the first signs of patent expirations in the pharmaceutical sector.

The patents on many of the drugs made in Ireland will expire over the next few years, which could have a significant effect on export sales as competition from generic rivals intensifies.

However, Davy also pointed out that volatility of such magnitude in the "modern sector" of the economy which includes pharmaceuticals is not uncommon.

Merrion Economics noted that most recent purchasing managers' (PMI) data suggests that the manufacturing sector picked up in October.