The 25-year-old is set to have a medical at the Premier League club on Tuesday.
Gabbiadini, who has six caps for Italy, joined Napoli from Sampdoria in 2015 and has scored 15 goals in 55 league appearances.
However, he has struggled for a first-team place in recent weeks and has not started a Serie A match since November.
Southampton are looking for extra forward cover, with Charlie Austin expected to be out for another three months with a shoulder injury.
Keep up to date with all the Premier League transfers in January as we track and profile all the players leaving or joining a club this month.
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The Bank of Scotland facility has been secured against the company's inventory of whisky stocks.
Thai-owned Inver House said the new facility would help the business improve its margins over the next five years.
It will also provide "increased headroom" to support overseas expansion in India, Kazakhstan and Poland.
Inver House's brand portfolio includes Old Pulteney, Balblair, anCnoc and Speyburn single malts.
A year ago, the Airdrie-based distiller announced it had completed a £10m investment programme which included boosting production capacity at its Speyburn distillery in Moray.
Inver House financial director Roger Hall said: "The new facility is significantly better value for us. It gives us access to the most cost-effective borrowing, which is crucial to our business.
"It also helps us to continue investment in our whisky stocks, which will see our brands grow over the next 12 years and beyond."
Inver House, which is owned by ThaiBev, currently employs 210 people across its six sites in Scotland.
In October, it reported a sharp fall in revenue and profits for 2015. The firm largely attributed the results to a reduction in sales of bulk whiskies and other "value-for-money" products.
It also cited a major reorganisation of distribution arrangements in its key US market.
Southampton have agreed a fee of about £14m for Napoli striker Manolo Gabbiadini.
[NEXT_CONCEPT]
Scotch whisky producer Inver House Distillers has secured a £45m bank lending deal to support growth plans.