Accounts for the facility in Co Offaly show that it has posted total pre-tax profits of just over €38m between 2012 and last year.
More than 300 people are to be laid off after the US company said it will close the site by 2026.
The Irish manufacturing operation, whose annual wage bill tops €13m, has also been heavily backed by the State.
The most recently filed set of accounts for the Irish unit show that it has received total grants of more than €6m from government agencies.
“Capital and revenue grants received from governmental agencies can be repayable in certain circumstances where the conditions of the grant agreements are not met by the company,” the accounts say.
Cardinal Health CEO Jason Hollar told investors earlier this month, as the group delivered full-year results, that it had enjoyed a “strong year of operational execution and record financial results”.
It reported revenue of $226.8bn (€205bn) for the last financial year, which was up 11pc year-on-year. Its operating profit rose 65pc to $1.2bn.
The results exceeded the company’s own expectations.
“As we turn the page to fiscal year ‘25, our confidence is reinforced by our strong and resilient business, with positive industry trends supporting our growth,” Mr Hollar told investors.
“And we continue to take actions to optimise not only the performance of our businesses, but also the financial strength of the broader enterprise.”
Underlining the contribution of the Irish operation to the US group, the Irish Times reported that an Irish unit of Cardinal Health paid a $100m (€90m) dividend to its US parent earlier this year.
The Irish unit was bought by Cardinal Health from US firm Medtonic in 2017 as part of a wider deal to acquire Medtronic’s patient product portfolio for $6.1bn (€5.5bn).
The operation in Co Offaly has previously undergone restructuring and seen previous layoffs.
In its 2021 financial year, it incurred just over €2m in restructuring costs, which followed a more than €500,000 charge it incurred the previous year.
“Restructuring costs relate primarily to termination benefits provided to employees under a programme to realign resources and right size the business going forward,” the 2021 accounts for the Irish business note.
Trade union Siptu said that it will begin negotiations with Cardinal Health management regarding the planned closure.
“The plant was a major employer in Tullamore and the surrounding area for more than four decades, this closure will have a devastating impact on our members, their families, the wider community and the local economy,” said Siptu organiser Ashling Dunne.
“The workers have provided loyal and dedicated service to their employer for many decades and have been left deeply upset at the decision to close the plant.”
Ms Dunne said that the union would meet with management under the statutory 30-day collective redundancy period “to explore all alternative options that could reduce the impact of these job losses”.
Cardinal Health staff in Tullamore were told this week that the company will shift production from the Irish site to facilities in Mexico and Costa Rica.
“Commercial activities in Ireland will not be impacted by these plans,” the group said in a statement.
“This decision is part of our regular assessment of our global business, manufacturing and supply chain operations to ensure we are able to meet the evolving needs of our customers, the industry and our business.”