The company floated in April, raising $31.5m and making paper millionaires of Boru Vodka founders David Phelan and Pat Rigney. Formerly executives with Diageoowned Baileys, they also got 4m when their firm, Roaring Water Spirits Group, merged with Castle Brands in 2003.

The latter floated in the US last April, then valuing the firm at $108m ( 89m). Its shares have since slipped, giving it a market capitalisation of just over $91m ( 71.7m).

Rigney's 3.5% stake is currently worth $3.2m, while Phelan's 4% is worth $3.6m.

Other shareholders in Castle Brands include Carbery Milk Products, which distills Boru. Its stake is worth roughly $6.75m. Clontarf Irish Whiskey is produced by John Teeling's Cooley Distillery.

British beer giant Interbrew produces a Boru vodka readyto-drink range.

Castle Brands said last week that it sold a total of almost 150,000 cases of spirits in the US in the last fiscal year and added that Boru Vodka had benefited greatly from "intense interest" in the brand. It sold over 117,000 cases of it outside the US.

Mark Andrews, chief executive of Castle Brands, said the company is "well positioned" to make "significant gains" in the US market, particularly with its Boru Vodka and Gosling's rum.