Botox plant to stay in Mayo

The company has just bought Allergan - which has a large factory in Westport, Co Mayo - for about €53bn. The deal brings its Irish workforce to 1,500 across Clondalkin, Baldoyle, Dundalk and a city centre office as well as the Westport site.

The company is committed to Ireland and has plans to expand, chief operating officer Bob Stewart told the Sunday Independent. This won't mean a new factory - it will more likely expand at its existing site in Clondalkin.

The Westport facility "will continue as normal" he said.

Botox going off patent will not change this, Mr Stewart added. "Botox is off patent but it is a biological product, it is complicated to make. It is a very durable asset."

He differentiated his company from rival drugmaker Pfizer. "We build blockbuster franchises rather than blockbuster drugs - product lines that we can group our sales force and branding around. This is more sustainable."

Pfizer will have difficulty finding a use for the Cork facilities it configured to make Lipitor now that the blockbuster drug has gone off patent, Mr Stewart added.

"Their plant is only configured for that. Once a plant that is producing global volumes of a single drug loses that volume, it is very, very difficult to find a product that uses similar technology and can fill that capacity."

Ireland made a mistake by focusing too heavily on attracting investment based on blockbuster drugs, he said.

The Actavis-Allergan deal was not motivated by tax, he added, since Actavis was already headquartered in Ireland before the deal.

However, international scrutiny of Ireland's tax regime "is certainly something that investors and analysts pay attention to", Mr Stewart added.

"Any further changes to tax policy could certainly create a disincentive [to investing in Ireland]… we like stability and knowing what to plan for", he said. "It is something we always have to be mindful of".