The influence of other drugs on the metabolism of viagra 50mg
The metabolism of viagra 50mg occurs primarily in the liver under the influence of CYP3A4 (major route) and CYP2C9 may therefore inhibitors of these isoenzymes may reduce viagra 50mg clearance and inducers, respectively, to increase viagra 50mg clearance.
With the simultaneous application of inhibitors of CYP3A4 (eg ketoconazole, erythromycin, cimetidine) reduced clearance of viagra 50mg.
Cimetidine (800 mg), a nonspecific inhibitor of CYP3A4, whereas admission to viagra 50mg (50 mg) leads to an increased plasma concentration of viagra 50mg by 56%.
A single dose of 100 mg of sildenafil in combination with erythromycin, a specific inhibitor of CYP3A4 (erythromycin, when taking two doses of 500 mg over 5 days) on the bottom of a consistent level of erythromycin in the blood to reach leads to an increase of sildenafil AUC by 182%.
With the concomitant use of sildenafil (single dose of 100 mg) and saquinavir, which is an inhibitor of HIV protease and an inhibitor of CYP3A4 (when using saquinavir a dose of 3-1200 mg) at a constant level of background saquinavir in the blood to reach, Cmax of sildenafil in the blood increased by 140% and AUC increased by 210%. Sildenafil has no effect on saquinavir pharmacokinetics.
More potent inhibitors of CYP3A4 such as ketoconazole or itraconazole may lead to more pronounced changes in the pharmacokinetics of sildenafil.
Concomitant use of sildenafil (single dose of 100 mg) and ritonavir, an inhibitor of HIV protease and a potent inhibitor of cytochrome P450 (when receiving ritonavir 500 mg, 2) the substance to reach a constant level in the ritonavir blood, Cmax of sildenafil was increased by 300% (4 times), and AUC of 1000% (11 times). After 24 hours the concentration in plasma sildenafil is approximately 200 ng / ml (via a single sildenafil - 5 ng / ml). generic viagra online cheap
In patients with erectile dysfunction and stable angina pectoris who regularly take anti-anginal drugs (except nitrates) and used a sildenafil 100 mg once a day, there was an increase in the duration of the treadmill test (19.9 with a confidence interval 95% -38.9 0.9 a) and the median time to worsening of symptoms of angina pectoris, 423.6 and 403.7 s to exercise compared with placebo.
In patients with concomitant hypertension, in which simultaneously two or more antihypertensive drugs, viagra 50mg at a dose of 100 mg once daily improved erections in 71%, increased the number of successful sexual attempts with 62%. The number of adverse events was similar compared with patients in other populations, containing three or more antihypertensive agents.
In all studies, using PDE-5, including viagra 50mg, reported nearterialnoy anterior ischemic optic neuropathy (NAION), which is the reason for the reduction or loss of vision. Most of these patients had risk factors such as the ratio of the reduced depth / surface ("hard surface"), age over 50 years, diabetes mellitus, hypertension, coronary heart disease, hyperlipidemia and smoking. There was no solid causal links between the use of PDE-5-inhibitors and the occurrence of ischemic optic neuropathy. Physicians should advise patients who have evidence of ischemic optic neuropathy, a possible recurrence of NAION. Patients should be advised to immediately consult a physician in case of a sudden deterioration of vision.
In patients with age-retinal degeneration viagra 50mg 100 mg once inside the day was well tolerated and caused no clinical effect in the study of visual function tests (visual acuity, grid Amsler, color recognition, "a stream of artificial light", and perimetry in photostress Gamfreyu.)