A man in his 60s died hours after taking Viagra this month, becoming the first reported fatality in Japan linked to the hugely popular anti-impotence drug, the Health and Welfare Ministry announced Wednesday. The man also had been taking nitroglycerin for high blood pressure, diabetes and irregular pulse. U.S.-based manufacturers of Viagra warn buyers not to take the drug when they are also on nitroglycerin because the combination can cause blood pressure to drop suddenly. The warning comes with each bottle of pills.