I have a feeling that it is a medical problem, but i do not want to leave my parents without medical help or money for a new car. Levitra belongs to the class of medicines known as phosphodiesterase type 5 (pde5) inhibitors and relaxes the muscles in the penis. Eight- to 12-week-old female c57bl/6 nude mice were purchased from charles river laboratories (sulzfeld, germany) or harlan laboratories (horst, the netherlands).