Sildenafil citrate (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg). Sildenafil at steady state, at a dose not approved for the treatment of erectile dysfunction (80 mg t.i.d.) resulted in a 50% increase in AUC and a 42% increase in C max of bosentan (125 mg b.i.d.). 13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of FertilityCarcinogenesisSildenafil 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 20- and 38- times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 100 mg. Sildenafil was not carcinogenic when administered to mice for 18 to 21 months at dosages up to the Maximum Tolerated Dose (MTD) of 10 mg/kg/day, approximately 0.4 times the MRHD on a mg/m2 basis in a 50 kg subject. 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 20- and 38- times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 100 mg. Sildenafil was not carcinogenic when administered to mice for 18 to 21 months at dosages up to the Maximum Tolerated Dose (MTD) of 10 mg/kg/day, approximately 0.4 times the MRHD on a mg/m2 basis in a 50 kg subject.
2.4 Dosage Adjustments Due to Drug Interactions
At the end of the long-term study, 88% of patients reported that sildenafil citrate improved their erections.Men with untreated ED had relatively low baseline scores for all aspects of sexual function measured (again using a 5-point scale) in the IIEF. Sildenafil citrate improved these aspects of sexual function: frequency, firmness and maintenance of erections; frequency of orgasm; frequency and level of desire; frequency, satisfaction and enjoyment of intercourse; and overall relationship satisfaction.One randomized, double-blind, flexible-dose, placebo-controlled study included only patients with erectile dysfunction attributed to complications of diabetes mellitus (n=268). As in the other titration studies, patients were started on 50 mg and allowed to adjust the dose up to 100 mg or down to 25 mg of sildenafil citrate; all patients, however, were receiving 50 mg or 100 mg at the end of the study. There were highly statistically significant improvements on the two principal IIEF questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) on sildenafil citrate compared to placebo. On a global improvement question, 57% of sildenafil citrate patients reported improved erections versus 10% on placebo.
Storage Requirements
Diary data indicated that on sildenafil citrate, 48% of intercourse attempts were successful versus 12% on placebo.One randomized, double-blind, placebo-controlled, crossover, flexible-dose (up to 100 mg) study of patients with erectile dysfunction resulting from spinal cord injury (n=178) was conducted. The changes from baseline in scoring on the two end point questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) were highly statistically significantly in favor of sildenafil citrate. On a global improvement question, 83% of patients reported improved erections on sildenafil citrate versus 12% on placebo. Diary data indicated that on sildenafil citrate, 59% of attempts at sexual intercourse were successful compared to 13% on placebo.Across all trials, sildenafil citrate improved the erections of 43% of radical prostatectomy patients compared to 15% on placebo.Subgroup analyses of responses to a global improvement question in patients with psychogenic etiology in two fixed-dose studies (total n=179) and two titration studies (total n=149) showed 84% of sildenafil citrate patients reported improvement in erections compared with 26% of placebo. Diary data in two of the studies (n=178) showed rates of successful intercourse per attempt of 70% for sildenafil citrate and 29% for placebo.Efficacy Results in Subpopulations in Controlled Clinical StudiesA review of population subgroups demonstrated efficacy regardless of baseline severity, etiology, race and age. 14 CLINICAL STUDIES In clinical studies, sildenafil citrate 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. Sildenafil citrate was evaluated primarily at doses of 25 mg, 50 mg and 100 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).
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Sildenafil citrate was administered to more than 3,000 patients aged 19 to 87 years, with ED of various etiologies (organic, psychogenic, mixed) with a mean duration of 5 years.
5.8 Effects on Bleeding
Sildenafil citrate was effective in a broad range of ED patients, including those with a history of coronary artery disease, hypertension, other cardiac disease, peripheral vascular disease, diabetes mellitus, depression, coronary artery bypass graft (CABG), radical prostatectomy, transurethral resection of the prostate (TURP) and spinal cord injury, and in patients taking antidepressants/antipsychotics and anti-hypertensives/diuretics. Sildenafil citrate demonstrated statistically significant improvement compared to placebo in all 21 studies.
12.3 Pharmacokinetics
Sildenafil citrate (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg). Sildenafil at steady state, at a dose not approved for the treatment of erectile dysfunction (80 mg t.i.d.) resulted in a 50% increase in AUC and a 42% increase in C max of bosentan (125 mg b.i.d.). 13 NONCLINICAL TOXICOLOGY 13.1 Carcinogenesis, Mutagenesis, Impairment of FertilityCarcinogenesisSildenafil 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 20- and 38- times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 100 mg. Sildenafil was not carcinogenic when administered to mice for 18 to 21 months at dosages up to the Maximum Tolerated Dose (MTD) of 10 mg/kg/day, approximately 0.4 times the MRHD on a mg/m2 basis in a 50 kg subject. 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 20- and 38- times, for male and female rats, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 100 mg.
Do Not Take Viagra If You:
Sildenafil was not carcinogenic when administered to mice for 18 to 21 months at dosages up to the Maximum Tolerated Dose (MTD) of 10 mg/kg/day, approximately 0.4 times the MRHD on a mg/m2 basis in a 50 kg subject. 14 CLINICAL STUDIES In clinical studies, sildenafil citrate 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. Sildenafil citrate was evaluated primarily at doses of 25 mg, 50 mg and 100 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). Sildenafil citrate was administered to more than 3,000 patients aged 19 to 87 years, with ED of various etiologies (organic, psychogenic, mixed) with a mean duration of 5 years. Sildenafil citrate demonstrated statistically significant improvement compared to placebo in all 21 studies.
What should I do if I miss a dose of sildenafil?
The studies that established benefit demonstrated improvements in success rates for sexual intercourse compared with placebo.Efficacy Endpoints in Controlled Clinical StudiesThe effectiveness of sildenafil citrate 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, sildenafil 100 mg cost (3) sometimes, (4) most times, and (5) almost always or always. The studies that established benefit demonstrated improvements in success rates for sexual intercourse compared with placebo.Efficacy Endpoints in Controlled Clinical StudiesThe effectiveness of sildenafil citrate 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.
- Common side effects include headache and flushing.
- Some may experience nasal congestion or dizziness.
- Serious side effects require immediate medical attention.
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, sildenafil 100 mg cost (3) sometimes, (4) most times, and (5) almost always or always.
- Overdose symptoms may include dizziness, nausea, or prolonged erections.
- Seek emergency help if an erection lasts over 4 hours.
- Avoid excessive dosing to prevent adverse events.
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 StudiesThe 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 100 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 100 mg, showed similar results.
5.5 Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives
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 StudiesThe 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 100 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 100 mg, showed similar results.
How does sildenafil work (mechanism of action)?
Figure 6 shows that regardless of the baseline levels of function, subsequent function in patients treated with sildenafil citrate was better than that seen in patients treated with placebo. At the same time, on-treatment function was better in treated patients who were less impaired at baseline.Effect of Sildenafil citrate on Maintenance of Erection by Baseline ScoreEffect of Placebo on Maintenance of Erection by Baseline ScoreFigure 6. Effect of Sildenafil Citrate and Placebo on Maintenance of Erection by Baseline Score.The frequency of patients reporting improvement of erections in response to a global question in four of the randomized, double-blind, parallel, placebo-controlled fixed dose studies (1,797 patients) of 12 to 24 weeks duration is shown in Figure 7. These patients had erectile dysfunction at baseline that was characterized by median categorical scores of 2 (a few times) on principal IIEF questions. Erectile dysfunction was attributed to organic (58%; generally not characterized, but including diabetes and excluding spinal cord injury), psychogenic (17%), or mixed (24%) etiologies.
Serious Side Effects
Sixty-three percent, 74%, and 82% of the patients on 25 mg, 50 mg and 100 mg of sildenafil citrate, respectively, reported an improvement in their erections, compared to 24% on placebo. In the titration studies (n=644) (with most patients eventually receiving 100 mg), results were similar.Overall treatment p<0.0001Figure 7. Percentage of Patients Reporting an Improvement in ErectionsThe patients in studies had varying degrees of ED. One-third to one-half of the subjects in these studies reported successful intercourse at least once during a 4-week, treatment-free run-in period.In many of the studies, of both sildenafil tablets lp 100 mg fixed dose and titration designs, daily diaries were kept by patients. In these studies, involving about 1,600 patients, analyses of patient diaries showed no effect of sildenafil citrate on rates of attempted intercourse (about 2 per week), but there was clear treatment-related improvement in sexual function: per patient weekly success rates averaged 1.3 on 50 to 100 mg of sildenafil citrate vs 0.4 on placebo; similarly, group mean success rates (total successes divided by total attempts) were about 66% on sildenafil citrate vs about 20% on placebo.During 3 to 6 months of double-blind treatment or longer-term (1 year), open-label studies, few patients withdrew from active treatment for any reason, including lack of effectiveness. Figure 6 shows that regardless of the baseline levels of function, subsequent function in patients treated with sildenafil citrate was better than that seen in patients treated with placebo. At the same time, on-treatment function was better in treated patients who were less impaired at baseline.Effect of Sildenafil citrate on Maintenance of Erection by Baseline ScoreEffect of Placebo on Maintenance of Erection by Baseline ScoreFigure 6. Effect of Sildenafil Citrate and Placebo on Maintenance of Erection by Baseline Score.The frequency of patients reporting improvement of erections in response to a global question in four of the randomized, double-blind, parallel, placebo-controlled fixed dose studies (1,797 patients) of 12 to 24 weeks duration is shown in Figure 7. These patients had erectile dysfunction at baseline that was characterized by median categorical scores of 2 (a few times) on principal IIEF questions. Erectile dysfunction was attributed to organic (58%; generally not characterized, but including diabetes and excluding spinal cord injury), psychogenic (17%), or mixed (24%) etiologies. Sixty-three percent, 74%, and 82% of the patients on 25 mg, 50 mg and 100 mg of sildenafil citrate, respectively, reported an improvement in their erections, compared to 24% on placebo. In the titration studies (n=644) (with most patients eventually receiving 100 mg), results were similar.Overall treatment p<0.0001Figure 7.
- Sildenafil interacts with nitrates, causing dangerous blood pressure drops.
- Consult a doctor before starting if on other medications.
- Alcohol may reduce the effectiveness and increase side effects.
Percentage of Patients Reporting an Improvement in ErectionsThe patients in studies had varying degrees of ED. One-third to one-half of the subjects in these studies reported successful intercourse at least once during a 4-week, treatment-free run-in period.In many of the studies, of both sildenafil tablets lp 100 mg fixed dose and titration designs, daily diaries were kept by patients. In these studies, involving about 1,600 patients, analyses of patient diaries showed no effect of sildenafil citrate on rates of attempted intercourse (about 2 per week), but there was clear treatment-related improvement in sexual function: per patient weekly success rates averaged 1.3 on 50 to 100 mg of sildenafil citrate vs 0.4 on placebo; similarly, group mean success rates (total successes divided by total attempts) were about 66% on sildenafil citrate vs about 20% on placebo.During 3 to 6 months of double-blind treatment or longer-term (1 year), open-label studies, few patients withdrew from active treatment for any reason, including lack of effectiveness. At the end of the long-term study, 88% of patients reported that sildenafil citrate improved their erections.Men with untreated ED had relatively low baseline scores for all aspects of sexual function measured (again using a 5-point scale) in the IIEF. Sildenafil citrate improved these aspects of sexual function: frequency, firmness and maintenance of erections; frequency of orgasm; frequency and level of desire; frequency, satisfaction and enjoyment of intercourse; and overall relationship satisfaction.One randomized, double-blind, flexible-dose, placebo-controlled study included only patients with erectile dysfunction attributed to complications of diabetes mellitus (n=268).
- Physical activity might improve erectile response when combined with medication.
- Maintain a healthy weight for better sexual function.
- Lifestyle changes can enhance sildenafil efficacy over time.
As in the other titration studies, patients were started on 50 mg and allowed to adjust the dose up to 100 mg or down to 25 mg of sildenafil citrate; all patients, however, were receiving 50 mg or 100 mg at the end of the study. There were highly statistically significant improvements on the two principal IIEF questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) on sildenafil citrate compared to placebo. On a global improvement question, 57% of sildenafil citrate patients reported improved erections versus 10% on placebo. Diary data indicated that on sildenafil citrate, 48% of intercourse attempts were successful versus 12% on placebo.One randomized, double-blind, placebo-controlled, crossover, flexible-dose (up to 100 mg) study of patients with erectile dysfunction resulting from spinal cord injury (n=178) was conducted. The changes from baseline in scoring on the two end point questions (frequency of successful penetration during sexual activity and maintenance of erections after penetration) were highly statistically significantly in favor of sildenafil citrate. On a global improvement question, 83% of patients reported improved erections on sildenafil citrate versus 12% on placebo.
| Medication Class | Interaction Type | Effect | Clinical Significance |
|---|---|---|---|
| Nitrates | Additive hypotensive effect | Severe hypotension | Contraindicated |
| Alpha-blockers | Enhanced hypotension | Blood pressure drop | Use with caution |
| CYP3A4 inhibitors | Increased sildenafil levels | Prolonged or intensified side effects | Dose adjustment may be needed |
| Protease inhibitors | Elevated sildenafil levels | Increased adverse effects | Monitoring required |
Diary data indicated that on sildenafil citrate, 59% of attempts at sexual intercourse were successful compared to 13% on placebo.Across all trials, sildenafil citrate improved the erections of 43% of radical prostatectomy patients compared to 15% on placebo.Subgroup analyses of responses to a global improvement question in patients with psychogenic etiology in two fixed-dose studies (total n=179) and two titration studies (total n=149) showed 84% of sildenafil citrate patients reported improvement in erections compared with 26% of placebo. Diary data in two of the studies (n=178) showed rates of successful intercourse per attempt of 70% for sildenafil citrate and 29% for placebo.Efficacy Results in Subpopulations in Controlled Clinical StudiesA review of population subgroups demonstrated efficacy regardless of baseline severity, etiology, race and age. Sildenafil citrate was effective in a broad range of ED patients, including those with a history of coronary artery disease, hypertension, other cardiac disease, peripheral vascular disease, diabetes mellitus, depression, coronary artery bypass graft (CABG), radical prostatectomy, transurethral resection of the prostate (TURP) and spinal cord injury, and in patients taking antidepressants/antipsychotics and anti-hypertensives/diuretics.
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