Abstract: Methods of modifying the rate of systemic absorption of a drug administered to a subject by a pulmonary route, the method comprising covalently conjugating a hydrophilic polymer to a drug, wherein the drug has a half-life of elimination from the lung of less than about 180 minutes, to form a drug-polymer conjugate, wherein the drug-polymer conjugate has a net hydrophilic character and a weight average molecular weight of from about 50 to about 20,000 Daltons, and wherein the half-life of elimination from the lung of the drug-polymer conjugate is at least about 1.5-fold greater than the half-life of elimination from the lung of the drug, wherein the half-life of elimination from the lung is measured by bronchoalveolar lavage followed by assaying residual lung material.