Abstract: The present invention provides purine derivatives and pharmaceutically acceptable salts thereof which exhibit an inhibitory action towards nasal mucus secretion and are useful as pharmaceuticals for treatment of nasal secretion and rhinitis. The purine derivatives are represented by the following general formula: ##STR1## wherein R is alkyl or cycloalkyl, or optionally-substituted phenyl or phenylalkyl; R' is hydrogen or --COOX; and X is alkyl, alkenyl, alkoxyalkyl, phenyl or phenylalkyl. The compounds are useful as therapeutic and preventive agents for various types of rhinitis accompanied by acceleration of nasal mucus secretion and by the sneezing reflex such as allergic rhinitis. The compounds may be administered orally and exhibit low toxicity, little side effect and high safety. Accordingly, continuous long term administration of the pharmaceutical compositions may be performed for highly effective treatment of rhinitis.

Abstract: Antiallergic substances, are evaluated by measuring the amount of nasal secretion quantitatively using experimental animal models with nasal mucosal hypersensitivity.

Abstract: This invention provides a method of determining the behavior of drugs in living bodies, particularly those which contain a variety of active ingredients, like biological, natural drug and crude-drug preparations. It comprises administering a drug being tested to an animal, taking a blood sample from that animal, deproteinizing the plasma separated from the blood, intravenously administering the deproteinized plasma thus prepared to a different test animal, and examining the effect of drug exhibited in that test animal. The amount of active ingredients absorbed into the blood can be estimated by this indirect method even with special drugs including a variety of unknown and trace components.