Baytril is an antibiotic - so it's VERY important that it is only given under veterinary supervision (it's a prescription only medicine anyway so not really something for a first aid kit). Inappropriate use/dose of antibiotics can make buns very sick or even kill them as they can alter the good bacteria that the bun has for digesting food.
Metacam is a painkiller, it is also prescription only and inappropriate use can again cause damage (kidneys I think) and stomach ulceration. The right dosage is absolutely tiny. Again I would only give this under the supervision of a vet.
Infacol is a baby medicine which you can buy in a chemist, if your bun has a gassy tum, it helps to break the gas down so that your bun can pass it more easily. It is not absorbed by the body so in the 'normal' dosages, it is fairly safe. But again, at the risk of sounding like a stuck record, it should really only be used in an emergency - a bun with symptoms of a painful gut should be got to a vet ASAP.