A fast acting orally disintegrating film (ODF) for treatment of various medical conditions including emesis that has a simple formulation, easy to manufacture and has similar pharmacokinetic profile to currently commercially available orally administered drug products is provided. The ODF comprises an active pharmaceutical ingredient such as ondansetron or a pharmaceutical acceptable salt thereof in an amount of 2 to 24 mg, at least one hydrophilic film forming polymer in an amount of at least 8% by weight of the film, wherein the at least one hydrophilic film forming polymer is characterized by having a molecular weight of 5000 to 50000 Da, and a water soluble excipient in an amount of 10 to 30% by weight of the film. The present invention also provides a method for preparing the ODF that remains stable over a period of time under a normal pharmacologically storage condition and a method for treating or preventing various medical conditions such as nausea or vomiting or a treatment method mediated through antagonizing action of 5HT at 5-HT3 receptor by administering the ODF to a patient in need thereof.
