Food laced with Talaxian wormroot.
Talaxian wormroot is a plant from Talax, which causes unpleasant gas pains if consumed.
In 2377, Neelix served the con artist Gar food that had been laced with Talaxian wormroot, neglecting to tell him that "some people react badly". Neelix then told Gar that the "abdominal spasms" would worsen over 30-40 hours, unless he revealed where he had taken the Doctor so that an antidote could be administered. (VOY: "Critical Care")