This is definitely Dreamcatcher.
Suddenly, herds of forest animals flee past their cabin, followed by two military helicopters that announce the area is now quarantined. Jonesy and Beaver return to the cabin to find a trail of blood from the bedroom to the bathroom, where Rick is sitting semi-catatonic on the toilet, which is now covered in blood. Rick is thrown from the toilet, dead into the tub as a three-foot long lamprey like creature writhes and screams in the toilet. Beaver attempts to trap the creature under the toilet lid, but the creature breaks out and kills him.
However, it's toothpicks, not cigarettes, that result in Beaver's death.
While Jonesy searched futily for duct tape, Beaver attempted to reach for a lone, untouched toothpick on the floor, seeing as he has a habit for chewing on them. As he did so, whatever was in the toilet tried to bang its way out, making Beaver hold down again.
Finally, Beaver couldn't take it anymore, leaning off the toilet just enough for the creature to get out and knocked Beaver to the ground and go for the back of his neck. When it moved away, Beaver grabbed his glasses and looked at it, only to see a medium-sized worm-looking creature with rows of razor sharp teeth. Fending it off (And losing 4 of his fingers in the process), Jonesy returned with the tape, only to see Beaver batteling the worm. In order to save his friend, he told Jonesy to get out and shut the door. When he did so, the worm attacked and killed The Beav.