order viagra viagra generic http://viagralim.com/.  Rare but serious side effects include a prolonged erection that can lead to damage to the penis, vision problems, and hearing loss.  Common side effects include headaches, heartburn, and flushed skin. Sildenafil, sold as the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension.  It also results in dilation of the blood vessels in the lungs.  Onset is typically within 20 minutes and lasts for about 2 hours.
 It is unclear if it is effective for treating sexual dysfunction in women.  Sildenafil should not be taken by people on nitrates such as nitroglycerin (glycerin trinitrate), as this may result in a serious drop in blood pressure.  It is taken by mouth or injection into a vein.  It requires sexual arousal, however, to work.  Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis.
 Caution is advised in those with cardiovascular disease.