this invention provides a method for inhibiting adsorption of container - derived contaminants on a powdery or solid drug which comprises establishing a lower alcohol vapor phase within a container made , at least in part , of rubber or a plastic material . the method inhibits adsorption of container - derived substances on a drug to preclude development of insoluble particulate matter owing to said adsorption in an aqueous solution prepared extemporaneously without causing loss of the drug and avoiding the toxic effect of decomposition or degradation of the drug , thus insuring a long - term trouble - free stable shelf - life of the drug .