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Viagra maximum dosage per day


VIAGRA at 50 mg or mg helped approximately 4 out of 5 men get and keep erections hard enough for sex. * * Seventy-two percent, 80%, and 85% of the patients on 25 mg, 50 mg, and mg of VIAGRA, respectively, achieved erections hard enough for sex, compared to 50% on placebo. What Is The Maximum Dosage Of Viagra Per Day. Free Bonus Pills With Every Order. Cheapest Prices on Internet. Canada Licensed Doctors Prescribe ED Medication Online, VIPPS Pharmacy Ships to You Since Secure Medical has Processed over 2 Million Orders! What Is The Maximum Dosage Of Viagra Per Day. Cheapest Prices, Fast Shipping to U.S. and Internationally. No Prescription Required. Dosages Anywhere From mg to 40mg in stock.
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Always keep a current list of the drugs and supplements you take and review the list with your healthcare providers and your pharmacist. Erections do not last for four hours, however, a man has the ability to have an erection for up to four hours. However, this drug should only be used during pregnancy if clearly needed. Viagra maximum dosage per day Главная › Форумы › Раздел 1 › Viagra maximum dosage per day. В этой теме 0 ответов, 1 участник, последнее обновление ackelnareg 1 месяц, 2 нед. назад.  CLICK HERE CLICK HERE CLICK HERE CLICK HERE CLICK HERE See risks and benefits of VIAGRA® (sildenafil citrate). Talk to your doctor The maximum recommended dosing frequency is once per day. Be sure to tell your However, Viagra Connect is only available in 50mg doses. The initial recommended dose for the majority of men is 50mg, taken a maximum of once a genericcialistadalafil.onlineed dosage guidelines and administration information for Viagra (sildenafil citrate). The maximum recommended dosing frequency is once per genericcialistadalafil.online 25, . viagra online. viagra maximum dosage per day. Анонимный. Ответить Цитировать. Ответить в теме. Новая тема. Страница: 1. enter site cheap viagra canada. buy viagra. buy cheap viagra. compre al canadiense viagra. YlosJouby. Ответить Цитировать.

It is not possible to determine whether these reported events are related directly to the use of Viagra, to the patient's underlying risk factors for hearing loss, a combination of these factors, or to other factors [ see Warnings and Precautions 5. Non-arteritic anterior ischemic optic neuropathy NAION , a cause of decreased vision including permanent loss of vision, has been reported rarely post-marketing in temporal association with the use of phosphodiesterase type 5 PDE5 inhibitors, including Viagra.

Most, but not all, of these patients had underlying anatomic or vascular risk factors for developing NAION, including but not necessarily limited to: Administration of Viagra with nitric oxide donors such as organic nitrates or organic nitrites in any form is contraindicated. Use caution when co-administering alpha-blockers with Viagra because of potential additive blood pressure-lowering effects. When Viagra is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating Viagra treatment and Viagra should be initiated at the lowest dose [ see Dosage and Administration 2.

When Viagra mg was co-administered with amlodipine 5 mg or 10 mg to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [ see Warnings and Precautions 5.

Co-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil fold increase in AUC. It is therefore recommended not to exceed a maximum single dose of 25 mg of Viagra in a 48 hour period [ see Dosage and Administration 2. Stronger CYP3A4 inhibitors such as ketoconazole or itraconazole could be expected to have greater effects than seen with saquinavir.

A starting dose of 25 mg of Viagra should be considered in patients taking erythromycin or strong CYP3A4 inhibitors such as saquinavir, ketoconazole, itraconazole [ see Dosage and Administration 2. In a drug-drug interaction study sildenafil 50 mg given with alcohol 0. There are no data with the use of Viagra in pregnant women to inform any drug-associated risks for adverse developmental outcomes. Limited data indicate that sildenafil and its active metabolite are present in human milk.

There is no information on the effects on the breastfed child, or the effects on milk production. Viagra is not indicated for use in pediatric patients. Safety and effectiveness have not been established in pediatric patients. However, since higher plasma levels may increase the incidence of adverse reactions, a starting dose of 25 mg should be considered in older subjects due to the higher systemic exposure [ see Dosage and Administration 2.

A starting dose of 25 mg should be considered in patients with severe renal impairment [ see Dosage and Administration 2.

The pharmacokinetics of sildenafil in patients with severely impaired hepatic function Child-Pugh Class C have not been studied. A starting dose of 25 mg should be considered in patients with any degree of hepatic impairment [ see Dosage and Administration 2. In studies with healthy volunteers of single doses up to mg, adverse reactions were similar to those seen at lower doses but incidence rates and severities were increased.

In cases of overdose, standard supportive measures should be adopted as required. Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and it is not eliminated in the urine. Viagra sildenafil citrate , an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate cGMP -specific phosphodiesterase type 5 PDE5.

Sildenafil citrate is designated chemically as 1-[[3- 6,7-dihydromethyloxopropyl-1 H -pyrazolo[4,3- d ]pyrimidinyl ethoxyphenyl]sulfonyl]methylpiperazine citrate and has the following structural formula:.

Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3. Viagra is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and mg of sildenafil for oral administration. In addition to the active ingredient, sildenafil citrate, each tablet contains the following inactive ingredients: The physiologic mechanism of erection of the penis involves release of nitric oxide NO in the corpus cavernosum during sexual stimulation.

NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate cGMP , producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.

Sildenafil enhances the effect of NO by inhibiting phosphodiesterase type 5 PDE5 , which is responsible for degradation of cGMP in the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum.

Sildenafil at recommended doses has no effect in the absence of sexual stimulation. Studies in vitro have shown that sildenafil is selective for PDE5. PDE3 is involved in control of cardiac contractility. Sildenafil is only about fold as potent for PDE5 compared to PDE6, an enzyme found in the retina which is involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision [ see Clinical Pharmacology In addition to human corpus cavernosum smooth muscle, PDE5 is also found in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle, brain, heart, liver, kidney, lung, pancreas, prostate, bladder, testis, and seminal vesicle.

The inhibition of PDE5 in some of these tissues by sildenafil may be the basis for the enhanced platelet antiaggregatory activity of NO observed in vitro , an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo.

Effects of Viagra on Erectile Response: Most studies assessed the efficacy of Viagra approximately 60 minutes post dose. The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours. Effects of Viagra on Blood Pressure: The decrease in sitting blood pressure was most notable approximately 1—2 hours after dosing, and was not different than placebo at 8 hours.

Similar effects on blood pressure were noted with 25 mg, 50 mg and mg of Viagra, therefore the effects are not related to dose or plasma levels within this dosage range.

Larger effects were recorded among patients receiving concomitant nitrates [ see Contraindications 4. In the following patients: Although plasma levels of sildenafil at 24 hours post dose are much lower than at peak concentration, it is unknown whether nitrates can be safely co-administered at this time point [ see Contraindications 4.

Three double-blind, placebo-controlled, randomized, two-way crossover studies were conducted to assess the interaction of Viagra with doxazosin, an alpha-adrenergic blocking agent. In the first study, a single oral dose of Viagra mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia BPH.

Following at least 14 consecutive daily doses of doxazosin, Viagra mg or matching placebo was administered simultaneously with doxazosin. Following a review of the data from these first 4 subjects details provided below , the Viagra dose was reduced to 25 mg. Thereafter, 17 subjects were treated with Viagra 25 mg or matching placebo in combination with doxazosin 4 mg 15 subjects or doxazosin 8 mg 2 subjects. The mean subject age was The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 25 mg Viagra or matching placebo are shown in Figure 2.

Blood pressure was measured immediately pre-dose and at 15, 30, 45 minutes, and 1, 1. No severe adverse events potentially related to blood pressure effects were reported in this group. Of the four subjects who received Viagra mg in the first part of this study, a severe adverse event related to blood pressure effect was reported in one patient postural hypotension that began 35 minutes after dosing with Viagra with symptoms lasting for 8 hours , and mild adverse events potentially related to blood pressure effects were reported in two others dizziness, headache and fatigue at 1 hour after dosing; and dizziness, lightheadedness and nausea at 4 hours after dosing.

There were no reports of syncope among these patients. For these four subjects, the placebo-subtracted mean maximum decreases from baseline in supine and standing systolic blood pressures were Both of these subjects were protocol violators, one due to a low baseline standing SBP, and the other due to baseline orthostatic hypotension. In the second study, a single oral dose of Viagra 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with BPH.

Following at least 14 consecutive days of doxazosin, Viagra 50 mg or matching placebo was administered simultaneously with doxazosin 4 mg 17 subjects or with doxazosin 8 mg 3 subjects. The mean subject age in this study was Twenty subjects received Viagra 50 mg, but only 19 subjects received matching placebo.

One patient discontinued the study prematurely due to an adverse event of hypotension following dosing with Viagra 50 mg. This patient had been taking minoxidil, a potent vasodilator, during the study. The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 50 mg Viagra or matching placebo are shown in Figure 3.

Blood pressure was measured after administration of Viagra at the same times as those specified for the first doxazosin study. In these two subjects, hypotension was reported as a moderately severe adverse event, beginning at approximately 1 hour after administration of Viagra 50 mg and resolving after approximately 7.

There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study. In the third study, a single oral dose of Viagra mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with BPH. In dose period 1, subjects were administered open-label doxazosin and a single dose of Viagra 50 mg simultaneously, after at least 14 consecutive days of doxazosin.

If a subject did not successfully complete this first dosing period, he was discontinued from the study. Subjects who had successfully completed the previous doxazosin interaction study using Viagra 50 mg , including no significant hemodynamic adverse events, were allowed to skip dose period 1. Treatment with doxazosin continued for at least 7 days after dose period 1. Thereafter, Viagra mg or matching placebo was administered simultaneously with doxazosin 4 mg 14 subjects or doxazosin 8 mg 6 subjects in standard crossover fashion.

Twenty-five subjects were screened. Two were discontinued after study period 1: Of the twenty subjects who were ultimately assigned to treatment, a total of 13 subjects successfully completed dose period 1, and seven had successfully completed the previous doxazosin study using Viagra 50 mg.

The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with mg Viagra or matching placebo are shown in Figure 4. Blood pressure was measured after administration of Viagra at the same times as those specified for the previous doxazosin studies. All three were taking Viagra mg, and all three reported mild adverse events at the time of reductions in standing SBP, including vasodilation and lightheadedness.

While there were no severe adverse events potentially related to blood pressure reported in this study, one subject reported moderate vasodilatation after both Viagra 50 mg and mg. There were no episodes of syncope reported in this study. When Viagra mg oral was co-administered with amlodipine, 5 mg or 10 mg oral, to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic.

Viagra 50 mg did not potentiate the hypotensive effect of alcohol 0. The maximum observed decrease in systolic blood pressure was The maximum observed decrease in diastolic blood pressure was There were no reports of postural dizziness or orthostatic hypotension.

The maximum recommended dose of mg sildenafil was not evaluated in this study [ see Drug Interactions 7. Effects of Viagra on Cardiac Parameters: Single oral doses of sildenafil up to mg produced no clinically relevant changes in the ECGs of normal male volunteers.

Studies have produced relevant data on the effects of Viagra on cardiac output. In one small, open-label, uncontrolled, pilot study, eight patients with stable ischemic heart disease underwent Swan-Ganz catheterization. A total dose of 40 mg sildenafil was administered by four intravenous infusions. Even though this total dosage produced plasma sildenafil concentrations which were approximately 2 to 5 times higher than the mean maximum plasma concentrations following a single oral dose of mg in healthy male volunteers, the hemodynamic response to exercise was preserved in these patients.

In a double-blind study, patients with erectile dysfunction and chronic stable angina limited by exercise, not receiving chronic oral nitrates, were randomized to a single dose of placebo or Viagra mg 1 hour prior to exercise testing. The primary endpoint was time to limiting angina in the evaluable cohort. The mean times adjusted for baseline to onset of limiting angina were These results demonstrated that the effect of Viagra on the primary endpoint was statistically non-inferior to placebo.

Effects of Viagra on Vision: At single oral doses of mg and mg, transient dose-related impairment of color discrimination was detected using the Farnsworth-Munsell hue test, with peak effects near the time of peak plasma levels. This finding is consistent with the inhibition of PDE6, which is involved in phototransduction in the retina. An evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of Viagra on visual acuity, intraocular pressure, or pupillometry.

Effects of Viagra on Sperm: There was no effect on sperm motility or morphology after single mg oral doses of Viagra in healthy volunteers. The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range. It is eliminated predominantly by hepatic metabolism mainly CYP3A4 and is converted to an active metabolite with properties similar to the parent, sildenafil.

Both sildenafil and the metabolite have terminal half lives of about 4 hours. Mean sildenafil plasma concentrations measured after the administration of a single oral dose of mg to healthy male volunteers is depicted below:.

Viagra is rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to minutes median 60 minutes of oral dosing in the fasted state. The mean steady state volume of distribution Vss for sildenafil is L, indicating distribution into the tissues.

Protein binding is independent of total drug concentrations. Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function Child-Pugh Class C have not been studied [ see Dosage and Administration 2.

A starting oral dose of 25 mg should be considered in those patients [ see Dosage and Administration 2. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance. The concomitant use of erythromycin or strong CYP3A4 inhibitors e.

Viagra had no effect on saquinavir pharmacokinetics. A stronger CYP3A4 inhibitor such as ketoconazole or itraconazole could be expected to have greater effect than that seen with saquinavir.

Population pharmacokinetic data from patients in clinical trials also indicated a reduction in sildenafil clearance when it was co-administered with CYP3A4 inhibitors such as ketoconazole, erythromycin, or cimetidine [ see Dosage and Administration 2.

This is consistent with ritonavir's marked effects on a broad range of P substrates. Viagra had no effect on ritonavir pharmacokinetics [ see Dosage and Administration 2. Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels.

In a study of healthy male volunteers, co-administration of sildenafil at steady state 80 mg t. Concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil. In healthy male volunteers, there was no evidence of a clinically significant effect of azithromycin mg daily for 3 days on the systemic exposure of sildenafil or its major circulating metabolite. Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors such as tolbutamide, warfarin , CYP2D6 inhibitors such as selective serotonin reuptake inhibitors, tricyclic antidepressants , thiazide and related diuretics, ACE inhibitors, and calcium channel blockers.

These effects on the metabolite are not expected to be of clinical consequence. No significant interactions were shown with tolbutamide mg or warfarin 40 mg , both of which are metabolized by CYP2C9. In a study of healthy male volunteers, sildenafil mg did not affect the steady state pharmacokinetics of the HIV protease inhibitors, saquinavir and ritonavir, both of which are CYP3A4 substrates.

Sildenafil at steady state, at a dose not approved for the treatment of erectile dysfunction 80 mg t. Sildenafil was not carcinogenic when administered to rats for 24 months at a dose resulting in total systemic drug exposure AUCs for unbound sildenafil and its major metabolite of and times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose MRHD of mg.

Sildenafil was negative in in vitro bacterial and Chinese hamster ovary cell assays to detect mutagenicity, and in vitro human lymphocytes and in vivo mouse micronucleus assays to detect clastogenicity.

In clinical studies, Viagra was assessed for its effect on the ability of men with erectile dysfunction ED to engage in sexual activity and in many cases specifically on the ability to achieve and maintain an erection sufficient for satisfactory sexual activity.

Viagra was evaluated primarily at doses of 25 mg, 50 mg and mg in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in duration, using a variety of study designs fixed dose, titration, parallel, crossover. Viagra was administered to more than 3, patients aged 19 to 87 years, with ED of various etiologies organic, psychogenic, mixed with a mean duration of 5 years.

Viagra demonstrated statistically significant improvement compared to placebo in all 21 studies. The studies that established benefit demonstrated improvements in success rates for sexual intercourse compared with placebo. Efficacy Endpoints in Controlled Clinical Studies. The effectiveness of Viagra was evaluated in most studies using several assessment instruments.

The primary measure in the principal studies was a sexual function questionnaire the International Index of Erectile Function - IIEF administered during a 4-week treatment-free run-in period, at baseline, at follow-up visits, and at the end of double-blind, placebo-controlled, at-home treatment. Two of the questions from the IIEF served as primary study endpoints; categorical responses were elicited to questions about 1 the ability to achieve erections sufficient for sexual intercourse and 2 the maintenance of erections after penetration.

The patient addressed both questions at the final visit for the last 4 weeks of the study. The possible categorical responses to these questions were 0 no attempted intercourse, 1 never or almost never, 2 a few times, 3 sometimes, 4 most times, and 5 almost always or always. Also collected as part of the IIEF was information about other aspects of sexual function, including information on erectile function, orgasm, desire, satisfaction with intercourse, and overall sexual satisfaction.

Sexual function data were also recorded by patients in a daily diary. In addition, patients were asked a global efficacy question and an optional partner questionnaire was administered. Efficacy Results from Controlled Clinical Studies. The effect on one of the major end points, maintenance of erections after penetration, is shown in Figure 6, for the pooled results of 5 fixed-dose, dose-response studies of greater than one month duration, showing response according to baseline function.

Results with all doses have been pooled, but scores showed greater improvement at the 50 and mg doses than at 25 mg. The pattern of responses was similar for the other principal question, the ability to achieve an erection sufficient for intercourse. The titration studies, in which most patients received mg, showed similar results. Figure 6 shows that regardless of the baseline levels of function, subsequent function in patients treated with Viagra was better than that seen in patients treated with placebo.

Since sildenafil clearance is reduced in patients with hepatic impairment e. With the exception of ritonavir for which co-administration with sildenafil is not advised see Section 4.

In order to minimise the potential of developing postural hypotension in patients receiving alpha-blocker treatment patients should be stabilised on alpha-blocker therapy prior to initiating sildenafil treatment. In addition, initiation of sildenafil at a dose of 25 mg should be considered see sections 4. The co-administration of PDE5 inhibitors, including sildenafil, with guanylate cyclase stimulators, such as riociguat, is contraindicated as it may potentially lead to symptomatic hypotension see section 4.

Agents for the treatment of erectile dysfunction, including sildenafil, should not be used in men for whom sexual activity is inadvisable e. VIAGRA is contraindicated in patients who have loss of vision in one eye because of non-arteritic anterior ischaemic optic neuropathy NAION , regardless of whether this episode was in connection or not with previous PDE5 inhibitor exposure see section 4.

The safety of sildenafil has not been studied in the following sub-groups of patients and its use is therefore contraindicated: A medical history and physical examination should be undertaken to diagnose erectile dysfunction and determine potential underlying causes, before pharmacological treatment is considered. Prior to initiating any treatment for erectile dysfunction, physicians should consider the cardiovascular status of their patients, since there is a degree of cardiac risk associated with sexual activity.

Sildenafil has vasodilator properties, resulting in mild and transient decreases in blood pressure see section 5. Prior to prescribing sildenafil, physicians should carefully consider whether their patients with certain underlying conditions could be adversely affected by such vasodilatory effects, especially in combination with sexual activity.

Patients with increased susceptibility to vasodilators include those with left ventricular outflow obstruction e. Serious cardiovascular events, including myocardial infarction, unstable angina, sudden cardiac death, ventricular arrhythmia, cerebrovascular haemorrhage, transient ischaemic attack, hypertension and hypotension have been reported post-marketing in temporal association with the use of VIAGRA.

Most, but not all, of these patients had pre-existing cardiovascular risk factors. Many events were reported to occur during or shortly after sexual intercourse and a few were reported to occur shortly after the use of VIAGRA without sexual activity. It is not possible to determine whether these events are related directly to these factors or to other factors.

Agents for the treatment of erectile dysfunction, including sildenafil, should be used with caution in patients with anatomical deformation of the penis such as angulation, cavernosal fibrosis or Peyronie's disease , or in patients who have conditions which may predispose them to priapism such as sickle cell anaemia, multiple myeloma or leukaemia. Prolonged erections and priapism have been reported with sildenafil in post-marketing experience.

In the event of an erection that persists for longer than 4 hours, the patient should seek immediate medical assistance. If priapism is not treated immediately, penile tissue damage and permanent loss of potency could result. Concomitant use with other PDE5 inhibitors or other treatments for erectile dysfunction. The safety and efficacy of combinations of sildenafil with other PDE5 inhibitors, or other pulmonary arterial hypertension PAH treatments containing sildenafil REVATIO , or other treatments for erectile dysfunction have not been studied.

Therefore the use of such combinations is not recommended. Cases of visual defects have been reported spontaneously in connection with the intake of sildenafil and other PDE5 inhibitors see section 4. Cases of non-arteritic anterior ischaemic optic neuropathy, a rare condition, have been reported spontaneously and in an observational study in connection with the intake of sildenafil and other PDE5 inhibitors see section 4.

Patients should be advised that in the event of any sudden visual defect, they should stop taking VIAGRA and consult a physician immediately see section 4. Caution is advised when sildenafil is administered to patients taking an alpha-blocker, as the co-administration may lead to symptomatic hypotension in a few susceptible individuals see section 4. This is most likely to occur within 4 hours post sildenafil dosing. In order to minimise the potential for developing postural hypotension, patients should be hemodynamically stable on alpha-blocker therapy prior to initiating sildenafil treatment.

Initiation of sildenafil at a dose of 25 mg should be considered see section 4. In addition, physicians should advise patients what to do in the event of postural hypotensive symptoms. Studies with human platelets indicate that sildenafil potentiates the antiaggregatory effect of sodium nitroprusside in vitro. There is no safety information on the administration of sildenafil to patients with bleeding disorders or active peptic ulceration.

Therefore sildenafil should be administered to these patients only after careful benefit-risk assessment. The film coating of the tablet contains lactose.

VIAGRA should not be administered to men with rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption. Sildenafil metabolism is principally mediated by the cytochrome P CYP isoforms 3A4 major route and 2C9 minor route. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.

Population pharmacokinetic analysis of clinical trial data indicated a reduction in sildenafil clearance when co-administered with CYP3A4 inhibitors such as ketoconazole, erythromycin, cimetidine.

Although no increased incidence of adverse events was observed in these patients, when sildenafil is administered concomitantly with CYP3A4 inhibitors, a starting dose of 25 mg should be considered. This is consistent with ritonavir's marked effects on a broad range of P substrates. Sildenafil had no effect on ritonavir pharmacokinetics. Based on these pharmacokinetic results co-administration of sildenafil with ritonavir is not advised see section 4.

Sildenafil had no effect on saquinavir pharmacokinetics see section 4. Stronger CYP3A4 inhibitors such as ketoconazole and itraconazole would be expected to have greater effects. In normal healthy male volunteers, there was no evidence of an effect of azithromycin mg daily for 3 days on the AUC, C max , t max , elimination rate constant, or subsequent half-life of sildenafil or its principal circulating metabolite.

Grapefruit juice is a weak inhibitor of CYP3A4 gut wall metabolism and may give rise to modest increases in plasma levels of sildenafil. Although specific interaction studies were not conducted for all medicinal products, population pharmacokinetic analysis showed no effect of concomitant treatment on sildenafil pharmacokinetics when grouped as CYP2C9 inhibitors such as tolbutamide, warfarin, phenytoin , CYP2D6 inhibitors such as selective serotonin reuptake inhibitors, tricyclic antidepressants , thiazide and related diuretics, loop and potassium sparing diuretics, angiotensin converting enzyme inhibitors, calcium channel blockers, beta-adrenoreceptor antagonists or inducers of CYP metabolism such as rifampicin, barbiturates.

In a study of healthy male volunteers, co-administration of the endothelin antagonist, bosentan, an inducer of CYP3A4 [moderate], CYP2C9 and possibly of CYP2C19 at steady state mg twice a day with sildenafil at steady state 80 mg three times a day resulted in Therefore, concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma concentrations of sildenafil.

Nicorandil is a hybrid of potassium channel activator and nitrate. Due to the nitrate component it has the potential to result in a serious interaction with sildenafil.

There are no data on the interaction of sildenafil and non-specific phosphodiesterase inhibitors such as theophylline or dipyridamole. Preclinical studies showed additive systemic blood pressure lowering effect when PDE5 inhibitors were combined with riociguat. In clinical studies, riociguat has been shown to augment the hypotensive effects of PDE5 inhibitors.

There was no evidence of favourable clinical effect of the combination in the population studied. Concomitant use of riociguat with PDE5 inhibitors, including sildenafil, is contraindicated see section 4. Concomitant administration of sildenafil to patients taking alpha-blocker therapy may lead to symptomatic hypotension in a few susceptible individuals. This is most likely to occur within 4 hours post sildenafil dosing see sections 4.

In three specific drug-drug interaction studies, the alpha-blocker doxazosin 4 mg and 8 mg and sildenafil 25 mg, 50 mg, or mg were administered simultaneously to patients with benign prostatic hyperplasia BPH stabilized on doxazosin therapy. When sildenafil and doxazosin were administered simultaneously to patients stabilized on doxazosin therapy, there were infrequent reports of patients who experienced symptomatic postural hypotension.

These reports included dizziness and light-headedness, but not syncope. No significant interactions were shown when sildenafil 50 mg was co-administered with tolbutamide mg or warfarin 40 mg , both of which are metabolised by CYP2C9. Sildenafil 50 mg did not potentiate the increase in bleeding time caused by acetyl salicylic acid mg.

Pooling of the following classes of antihypertensive medication; diuretics, beta-blockers, ACE inhibitors, angiotensin II antagonists, antihypertensive medicinal products vasodilator and centrally-acting , adrenergic neurone blockers, calcium channel blockers and alpha-adrenoceptor blockers, showed no difference in the side effect profile in patients taking sildenafil compared to placebo treatment.

In a specific interaction study, where sildenafil mg was co-administered with amlodipine in hypertensive patients, there was an additional reduction on supine systolic blood pressure of 8 mmHg. The corresponding additional reduction in supine diastolic blood pressure was 7 mmHg. These additional blood pressure reductions were of a similar magnitude to those seen when sildenafil was administered alone to healthy volunteers see section 5. Sildenafil mg did not affect the steady state pharmacokinetics of the HIV protease inhibitors, saquinavir and ritonavir, both of which are CYP3A4 substrates.

In healthy male volunteers, sildenafil at steady state 80 mg t. No relevant adverse effects were found in reproduction studies in rats and rabbits following oral administration of sildenafil. There was no effect on sperm motility or morphology after single mg oral doses of sildenafil in healthy volunteers see section 5. As dizziness and altered vision were reported in clinical trials with sildenafil, patients should be aware of how they react to VIAGRA, before driving or operating machinery.

The most commonly reported adverse reactions in clinical studies among sildenafil treated patients were headache, flushing, dyspepsia, nasal congestion, dizziness, nausea, hot flush, visual disturbance, cyanopsia and blurred vision. Because not all adverse reactions are reported to the Marketing Authorisation Holder and included in the safety database, the frequencies of these reactions cannot be reliably determined.

Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness. Medically important adverse reactions reported at an incidence greater than placebo in controlled clinical studies and medically important adverse reactions reported through post-marketing surveillance. Respiratory, thoracic and mediastinal disorders. Myalgia, Pain in extremity. Renal and urinary disorders.

Reproductive system and breast disorders. Chest pain, Fatigue, Feeling hot. Reporting suspected adverse reactions after authorisation of the medicinal product is important. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.

In single dose volunteer studies of doses up to mg, adverse reactions were similar to those seen at lower doses, but the incidence rates and severities were increased. Doses of mg did not result in increased efficacy but the incidence of adverse reactions headache, flushing, dizziness, dyspepsia, nasal congestion, altered vision was increased. In cases of overdose, standard supportive measures should be adopted as required.

Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and not eliminated in the urine. Sildenafil is an oral therapy for erectile dysfunction. In the natural setting, i.

The physiological mechanism responsible for erection of the penis involves the release of nitric oxide NO in the corpus cavernosum during sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate cGMP , producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.

Sildenafil has a peripheral site of action on erections. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum but potently enhances the relaxant effect of NO on this tissue. Therefore sexual stimulation is required in order for sildenafil to produce its intended beneficial pharmacological effects.

Studies in vitro have shown that sildenafil is selective for PDE5, which is involved in the erection process.

Physicians should advise patients to stop use of all PDE5 inhibitors, including Viagra, and seek medical attention in the event of a sudden loss of vision in one or both eyes. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance. Stronger CYP3A4 inhibitors such as ketoconazole and itraconazole would be expected to have greater effects. Viagra is formulated as blue, viagra maximum dosage per day, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and mg of sildenafil for oral administration. Qualitative and quantitative composition 3. Viagra maximum dosage per day
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