Poppers are a class of drug called alkyl nitrites: these are the amyl, butyl and isobutyl nitrites. They all have the same effect. They work on the cardiovascular (heart and blood) system by dilating blood vessels: basically making blood vessels larger so more blood gets to and from the heart. This results in a head rush, which some people find enjoyable.
Poppers are also said to relax the sphincter muscles in the anus, so it is unclear if the medication you mention is going to be affected by poppers. It would depend on what the medication is for. Taking poppers is dangerous if you have chest or heart problems, anaemia or glaucoma. If you are on medication to lower blood pressure poppers will make blood pressure fall further, often to dangerously low levels.
You can check likely side effects of your medication from the Patient Information Leaflet supplied with all medicines. Using poppers with alcohol is risky and using poppers with stimulant drugs such as ecstasy, cocaine or MCAT can put considerable strain on the heart. If any doubt it is safer not to use poppers.