Ear

This chapter deals with formulation and preparation of ear drops for application to the external auditory canal as well as those intended for the middle ear. Creams and ointments for the ear are similar to semisolid preparations for cutaneous use. The most used ear drops prepared in pharmacies are discussed for their formulation (solvent, pH, osmotic value, preservation), method of preparation, packaging, storage and methods of administration. The formulation of ear drops, especially the choice of the vehicle, depends on the site of action: the external auditory canal or the middle ear. When ear drops get to the middle ear, they may come into contact with the inner ear and so cause ototoxicity. Because of the ototoxicity of active substances, non-aqueous vehicles and many other excipients, special precautions are needed in formulations that should, or may accidentally, come into contact with the middle ear. Preparations intended for the middle ear are aqueous, sterile and preferably iso-osmotic. When non-aqueous vehicles are used in ear drops for the external auditory canal, it depends on the state of the patient’s ear drum whether they will reach the middle ear.