Definition: Nitrates are heart medicines, such as nitroglycerin, that relax and widen blood vessels so the heart needs less oxygen. MedlinePlus lists nitroglycerin as a vasodilator used to treat and prevent chest pain from angina. On ED pill labels, "nitrates" means these medicines in any form, used regularly or only now and then.
The Viagra label says it must not be used with nitric oxide donors such as organic nitrates or nitrites in any form, or with riociguat, because blood pressure can drop sharply. Cialis has the same contraindication. If a nitrate is needed in a life-threatening emergency, the Cialis label says at least 48 hours should pass after the last Cialis dose. The Stendra and vardenafil labels carry the same nitrate warning.
Nitroglycerin comes as tablets under the tongue, sprays, patches and ointment, and other nitrates come as daily pills. A medicine taken only for chest pain attacks still counts, which is why the labels say "used regularly or now and then".
Tadalafil lasts long enough that the timing of the last dose matters in an emergency. A medicine list that shows every PDE5 dose with its time, kept where a family member or paramedic can see it, answers the question an emergency team will ask.
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