take viagra when they need it. ask your doctor if your heart is healthy enough for sex. do not take viagra if you take nitrates for chest pain or adempas® for pulmonary hypertension. your blood pressure could drop to an unsafe level. to avoid long-term injury, seek immediate medical help for an erection lasting more than four hours. stop taking wbr id "wbr14223" viagra and call your doctor right away if you experience a sudden decrease or loss in vision or hearing. ask your doctor about viagra single packs. /b