Advantages and disadvantages of different routes of analgesic drug administration including rectal, oral transmucosal and intranasal routes are discussed. Although the rectal route has advantages of high bioavailability, rapid onset of action and usability by patients who cannot take medicines by mouth, some patients cannot tolerate suppositories. Transmucosal routes also have the advantages of lacking first pass effect by the liver and not having to take drugs by mouth. At present, a clinical trial is being conducted in Japan on rescue drugs by the oral transmucosal route. With the intranasal route, drug aerosol is administered into the nasal cavity and absorbed through the mucosa of the upper airway. Nebulized fentanyl has been reported. Selection of the route of administration should be made according to the patient's condition taking into consideration the advantages of each route of administration.