To obtain the subject medicinal agent containing a hetrocyclic compound having a specific structure as active ingredient, capable of preventing or treating septicemia, rheumatic inflammation. Crohn's disease, etc., through inhibiting nitrogen monoxide production.

This medicinal agent contains, as active ingredient, a 4- aminoquinazoline derivative of the formula [R1 is H, etc.; Ya is a 1-6C alkylene; Aa is CyAa-(R2a)1a, etc. (CyAa is a 3- to 7-membered monocyclic (saturated) carbon ring; R2a is H, etc.; (1a) is 1 or 2); CyBa is a 4- to 7-membered (saturated) heterocycle containing one N-atom; R3a is H, etc.; R4a is H, etc.; Za is methylene, etc.; (ma) and (na) are each 1 or 2] [e.g. 4-(1,1-dimethyl-2-methoxyethyl) amino-2-(1-imidazolyl)quinazoline] or a nontoxic salt, acid adduct or hydrate thereof. The compound of the formula inhibits nitrogen monoxide production by inhibiting the manifestation of the mRNA of nitrogen monoxide synthase.