Described are antihypertensive agents selected from the class consisting of 2[4(tetrahydro-2-furoyl)-piperazino]-4-amino-6,7-dimethoxyquinazoline and 2-[4(tetrahydropyran-2-carbonyl)-piperazinyl]-4-amino-6,7-dimethoxyquinazo line, and pharmaceutically acceptable acid addition salts thereof. The compounds are highly water soluble and can be administered in time release form as well as parenterally, including intravenously.