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HepaticSildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate and has the following structural formula: when to take viagra

Viagra was the first and is probably the most famous of the three PDE-5 inhibitors used to treat erectile dysfunction. Viagra was approved for erectile dysfunction in March 27, 1998. Viagra is manufactured by Pfizer, Inc.This can be one 25 mg tablet a day or one 50 mg tablet a day or one 100 mg tablet a day.Caution is advised when PDE5 inhibitors are co-administered with alpha-blockers. PDE5 inhibitors, including Levitra, and alpha-adrenergic blocking agents are both vasodilators with blood-pressure lowering effects. When vasodilators are used in combination, an additive effect on blood pressure may be anticipated. In some patients, concomitant use of these two drug classes can lower blood pressure significantly leading to symptomatic hypotension (for example, fainting) [see Drug Interactions (7.1) and Clinical Pharmacology (12.2)]. Consideration should be given to the following:

In a separate postmarketing study of 44 healthy volunteers, single doses of 10 mg Levitra resulted in a placebo-subtracted mean change from baseline of QTcF (Fridericia correction) of 5 msec (90% CI: 2,8). Single doses of gatifloxacin 400mg resulted in a placebo-subtracted mean change from baseline QTcF of 4 msec (90% CI: 1,7). When Levitra 10mg and gatifloxacin 400 mg were co-administered, the mean QTcF change from baseline was additive when compared to either drug alone and produced a mean QTcF change of 9 msec from baseline (90% CI: 6,11). The clinical impact of these QT changes is unknown [see Warnings and Precautions (5.7)].EF Domain Score viagra dosage Reporting of suspected adverse reactionsc.) OverdosingIn clinical studies, tadalafil was shown to augment the hypotensive effects of nitrates. This is thought to result from the combined effects of nitrates and tadalafil on the nitric oxide/cGMP pathway. Therefore, administration of CIALIS to patients who are using any form of organic nitrate is contraindicated (see section 4.5). increased redness of the eye

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Take riociguat, a guanylate cyclase stimulator, a medicine that treats pulmonary arterial hypertension and chronic-throembolic pulmonary hypertension.have had an erection that lasted for more than 4 hours

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Non-arteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision, has been reported rarely postmarketing in temporal association with the use of phosphodiesterase type 5 (PDE5) inhibitors, including Cialis. Most, but not all, of these patients had underlying anatomic or vascular risk factors for development of NAION, including but not necessarily limited to: low cup to disc ratio (“crowded disc”), age over 50, diabetes, hypertension, coronary artery disease, hyperlipidemia, and smoking. It is not possible to determine whether these events are related directly to the use of PDE5 inhibitors, to the patient's underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors [see Warnings and Precautions (5.4)].In the 6 month double-blind study, the treatment effect of Cialis did not diminish over time.