A powdery pharmaceutical composition and a powdery preparation in unit dosage form for application to the mucosa of the nasal cavity, at least about 90% of which consists of particles having an effective particle diameter of about 20 to about 250 microns, said composition comprising a lower alkyl ether of cellulose having a viscosity, determined at about 37.degree. C. for a 2% aqueous solution thereof, of at least about 5 centipoises and a pharmaceutically effective amount of a drug; and a method for treating or preventing a human nasal disease, which comprises administering a powdery preparation in unit dosage form to the nasal cavity of a human being requiring treatment or prevention of a nasal disease through his nostrils.