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A Double-blind Placebo-controlled Evaluation of the Effect of Topical Sildenafil on Erectile Dysfunction

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Several adverse effects have been reported with use of oral sildenafil in the treatment of erectile dysfunction (ED). In this study, a formulation of sildenafil topical gel was compared with sildenafil tablet in a randomized, double-blind, prospective, placebo-controlled clinical trial. A total of 94 patients, with clinically diagnosed ED were recruited. The patients were evaluated by treatment group, nature of ED, and age. The cases received a topical gel containing 1% sildenafil and placebo tablet, and the control group received 100 mg sildenafil tablet and a gel base (without drug) as placebo. The tablets were taken one hour before sexual activity and approximately 0.5 g of the topical gel was applied on the glans of the penis and was massaged for 5 minutes before sexual activity. In the case group, five patients (12.5%) had complete erection, five patients (12.5%) had moderate erection, and 30 patients (75%) had no erection. In the control group, these results were 28 (70%), 6 (15%) and 6 (15%) respectively. The onset of erection in the case group (in patients with complete erection) was 7.4 ± 3.6 minutes, but was 37.8 ± 14.9 minutes in the control group. Four cases of mild headache were observed in the case group. This was pain treated four minutes before receiving any drugs for headache. Two cases of severe headache were observed in the control group. In the control group, one patient developed disturbance in visual function and one patient developed severe dyspepsia. The findings suggest that sildenafil delivery using a transdermal formulation can be enhanced by several synthetic or natural percutaneous absorption enhancers, and appears to be a promising approach for the treatment ED.
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The Journal of Applied Research Vol. 5, No. 2, 2005 289
A Double-blind Placebo-controlled
Evaluation of the Effect of Topical
Sildenafil on Erectile Dysfunction
Mehdi Yonessi, MD*
Madjid Saeedi, PhD
*Department of Urology, Faculty of Medicine,Mazandaran University of Medical Sciences,
Sari, Iran
Department of Pharmaceutics, Faculty of Pharmacy,Mazandaran University of Medical
Sciences, Sari, Iran
onset of erection in the case group (in
patients with complete erection) was 7.4
±3.6 minutes,but was 37.8 ± 14.9 min-
utes in the control group. Four cases of
mild headache were observed in the
case group. This was pain treated four
minutes before receiving any drugs for
headache. Two cases of severe headache
were observed in the control group. In
the control group,one patient devel-
oped disturbance in visual function and
one patient developed severe dyspepsia.
The findings suggest that sildenafil
delivery using a transdermal formula-
tion can be enhanced by several syn-
thetic or natural percutaneous
absorption enhancers,and appears to be
a promising approach for the treatment
ED.
INTRODUCTION
Erectile dysfunction (ED) is a common
problem with a prevalence of approxi-
mately 50% in men aged 40 to 70 years.1
Sildenafil citrate,a selective inhibitor of
cyclic guanosine monophosphate
(cGMP)-specific phosphodiesterase
type 5 (PDE5), is an effective oral treat-
ment of ED.2The physiologic mecha-
nism of erection involves release of
nitric oxide in the corpora during sexual
stimulation. This release activates the
enzyme guanylate cyclase and results in
KEY WO R D S : erectile dysfunction,
s i l d e n a f i l , t o p i c a l , t r a n s d e r m a l , a d v e r s e
e f f e c t
ABSTRACT
Several adverse effects have been
reported with use of oral sildenafil in
the treatment of erectile dysfunction
(ED). In this study,a formulation of
sildenafil topical gel was compared with
sildenafil tablet in a randomized, dou-
ble-blind, prospective,placebo-con-
trolled clinical trial. A total of 94
patients,with clinically diagnosed ED
were recruited. The patients were evalu-
ated by treatment group,nature of ED,
and age. The cases received a topical gel
containing 1% sildenafil and placebo
tablet, and the control group received
100 mg sildenafil tablet and a gel base
(without drug) as placebo. The tablets
were taken one hour before sexual
activity and approximately 0.5 g of the
topical gel was applied on the glans of
the penis and was massaged for 5 min-
utes before sexual activity.In the case
group,five patients (12.5%) had com-
plete erection, five patients (12.5%) had
moderate erection, and 30 patients
(75%) had no erection. In the control
group,these results were 28 (70%), 6
(15%) and 6 (15%) respectively. The
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Vol. 5, No. 2, 2005 The Journal of Applied Research
290
increased levels of cGMP. This increased
cGMP relaxes the smooth muscle in the
corpus cavernosum and allows greater
inflow of blood, thus increasing the
intracavernosal pressure compressing
the peripheral venules and leading to an
erection. The main action of sildenafil is
the enhancement of the effect of nitric
oxide by inhibiting the cGMP-specific
PDE5 degradation.3
The main adverse effects reported
in clinical trials were headache,dyspep-
sia, visual disturbance (changes in per-
ception of color hue or brightness),
flushing,and rhinitis. These were mild in
severity and the number of discontinua-
tions because of adverse effects was
small (< 1%).
In a prospective study,the adverse
reactions most commonly observed were
flushing (30.8%), headache (25.4%),
nasal congestion (18.7%), and heartburn
(10.5%).3All events were short lived
and mild in nature,with 31.6% of
patients experiencing one or more
adverse events. There was a significant
association between higher doses and
the occurrence of side effects.
In a recent study,no pattern of
errors was evident in any visual function
test following sildenafil administration.5
Sildenafil has been associated with a
mild decrease in systemic arterial pres-
sure as well as a synergistic and often
major decrease in systemic arterial pres-
sure in the presence of organic nitrates.6-
8Priapism (painful or uncomfortable
erection persisting for several hours
after ejaculation) was reported in one
case.9In another study,the number of
deaths associated with sildenafil citrate
and injections of alprostadil, both of
which are used exclusively in the treat-
ment of ED,were compared based on
the number of deaths per filled prescrip-
tion for these agents reported to the
FDA.10 The results showed that the
number of deaths per prescriptions filled
for sildenafil was significantly greater
than that for injections of alprostadil.
Repeated doses of oral sildenafil are
required to sustain plasma levels
because of its short duration of action
(t1/2 = 1 h) with high liver metabolism.11
Thus,topical delivery through local tis-
sue area may be an alternative to oral
administration to reduce the incidence
of adverse effects,increase the time to
onset of response,and sustain effects for
longer periods.Furthermore,transder-
mal delivery of sildenafil can offer sev-
eral advantages over conventional
dosage forms and the multiple dosing
can be eliminated.12 However,transder-
mal permeation of compounds in the
local skin, in general, is slow due to low
permeability resulting from physico-
chemical properties of the compound,
low partition ability,and the tissue barri-
er from the stratum corneum, which cre-
ates a low diffusion coefficient.13 Liaw
showed that after transdermal adminis-
tration of 15.8 µg/mL of sildenafil to
nude mouse skin, it was detected in the
bloodstream as early as 15 minutes.12
The transport amount of sildenafil could
be quantitated and, at pH of 8 to 11, had
the highest permeation rate in nude
mouse skin.
In the present study,sildenafil topi-
cal gel was compared with sildenafil
tablet in a double-blind, placebo-control
clinical trial.
MATERIALS AND METHODS
The following chemicals were used:
Methylparaben and propylparaben,
polyethylene glycol (PEG) 200, PEG
300, PEG 400, isopropyl alcohol, glyc-
erin, ethanol, KH2PO4,NaOH (supplied
by Merck), HPMC K100M (supplied by
Colorcon). The sildenafil powder was
provided by Razak Company, Tehran,
Iran. The sildenafil tablets were pur-
chased from Rouz Daru Company,
Tehran, Iran.
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The Journal of Applied Research Vol. 5, No. 2, 2005 291
Preparation of the Formulations
Several agents (PEG 200, 300, 400;
ethanol, propylene glycol, glycerin) were
used as cosolvent for sildenafil in water
and a buffer (pH 7.4). The solubility of
sildenafil in several systems was deter-
mined spectrophotometerically at 223
nm. The linearity interval established
was 10-30 µg/mL (r2= 0.9997).14
HPMC K100M was dispersed in
preserved buffer (methylparaben 0.18%
and propylparaben 0.02%) and ethanol
for overnight. The sildenafil powder
(1%)15 was dissolved in solvent system
before the addition of polymer and
stirred with a double bladed mixer (Ika-
werk, Germany) 500 rpm for 30 minutes
and then added to polymer dispersion
and stirred till gel forming. The formula-
tions were kept in 4˚C,25˚C,and 40˚C
for physical stability evaluation during a
two-week period. The drug release from
gel base and percutaneous absorption
was determined in vitro. Final formula-
tions for clinical trial were controlled
microbiologically based on USP XXIV.16
Clinical Trial
The study design was a randomized
(block-random sampling), double blind,
prospective,placebo-controlled trial.
Under the assumption of an overall
mean difference of 0.5 units and a stan-
dard deviation of 0.5 units,78 patients
were required to achieve a power of
95% to reject a null hypothesis of equal-
ity,applying a two-sided test at the 5%
significance level.
All patients with ED (n = 94) who
presented to one urologist from July
2003 to May 2004 were considered for
inclusion in the study.Men with anatom-
ical defects of the penis,other sexual dis-
orders,spinal cord injury,major
psychiatric disorder,poorly controlled
diabetes,stroke,a heart attack within six
months,treatment with organic nitrate,
active peptic ulcer disease,migraine,
vision disorders,and allergic rhinitis,
were excluded. A total of 14 patients
were excluded from the trial based on
these criteria. Thus,80 patients with clin-
ically diagnosed ED were included in
the analysis.
In recognition of the multifactorial
nature of ED,men with a broad variety
of baseline etiologies were enrolled in
the trial, including those with ED of
Figure 1. Comparison of the effect of sildenafil on ED in oral and transdermal administration.
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292
organic,psychogenic,and mixed causes.
Patients were divided categories by age
(ie, < 50 and 50) and by ED etiology.
The case group received a topical
gel containing 1% sildenafil and placebo
tablet, and the control group received
100 mg sildenafil tablet and gel base
(without drug) as placebo. The tablets
were taken one hour before sexual
activity and approximately 0.5 g of the
topical gel was applied to the glans of
penis and was massaged for five minutes
before sexual activity.
The overall clinical response was
assessed by erection (complete,moder-
ate,and none) and the onset of erection.
Headache,dyspepsia, rhinitis,diarrhea,
heartburn, visual dysfunction, and pri-
apism were studied as adverse drug
reactions. The patients were followed for
up to two weeks.
Statistical Analysis
Student ttest, and Chi-square test were
used to determine significant differences
between groups,and a Pvalue of < 0.05
was considered statistically significant.
RESULTS
A total of 24 solvent systems were inves-
tigated and the percent of solubility was
determined. These results showed the
best solubility in media buffer compared
with distilled water.Of these solvents,
ethanol showed the best results.Several
formulations of the topical gel formula-
tions were investigated (data not
shown). Carbopol did not show suitable
results in selected systems and this find-
ing could not be explained by the low
ratio of water in selected systems.
Several kinds of HPMC were tested as
gelling agent and, of these,HPMC
K100M showed the best results.
After evaluation of the physical sta-
bility of formulations,the most stable
gels were chosen for clinical trial. The
release profile of one selected formula-
tion was studied in vitro. These results
showed that ethanol had the most effect
on the release profile of sildenafil.
Patient characteristics are shown in
Table 1. Fourteen patients were exclud-
ed from the efficacy analyses: nine
patients were given another drugs that
stimulated erection and five patients suf-
fered from other disorders during study.
In the case group,five patients
(12.5%) had complete erection, five
patients (12.5%) had moderate erection,
and 30 (75%) had no erection (Figure
1). In the control group,these results
were 28 (70%), six (15%), and six
(15%), respectively.
The onset of erection was 7.4 ± 3.6
minutes in the case group (in patients
with complete erection), and was 37.8 ±
14.9 minutes in the control group.
Four patients experienced mild
headache in the case group. This pain
was treated four minutes before receiv-
ing any drugs.In the control group,two
patients developed severe headache,one
experienced disturbance in visual func-
tion, and one patient experienced severe
dyspepsia.
DISCUSSION
Despite the proven efficacy of oral ther-
apy for ED,some patients are unable to
take these medications because of drug
interactions,side effects,or a lack of
Table 1. Patient Characteristics
Case Control
Age
Mean (year) 47.2 50.8
Range 26-63 37-65
Duration of ED (month)
Mean 17.5 18.1
Range 7-34 7-36
Nature of ED
Organic 17 16
Psychogenic 23 24
Mixed … …
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The Journal of Applied Research Vol. 5, No. 2, 2005 293
tablet. For example,only 5% of patients
in this study reported headache com-
pared with 25.4% of sildenafil-treated
patients in a study by Baylor et al3and
16.0% in a study by Morales et al4.
Visual disorders was reported in 5.8%
and 3.0% of patients in the Baylor and
Morales studies—an incidence that is
similar to that found in our study.No
cases of heartburn were observed in our
study,however,it seems that our exclu-
sion criteria may explain this subject.
Flushing and nasal congestion were not
observed in our study.
This investigation is the first con-
trolled-randomized trial on sildenafil in
Iran. Thus,further studies are needed for
evaluation of sildenafil tablet side
effects in our country.
CONCLUSION
In conclusion, sildenafil delivery using a
transdermal formulation can be
enhanced by several synthetic or natural
percutaneous absorption enhancers,and
appears to be a promising approach for
the treatment ED.
ACKNOWLEDGMENT
This work was supported by a grant
from the research council of the
Mazandaran University of Medical
Sciences. We would like to thank Dr.
Khorrami (Targolshimi Company) for
her help,Colorcon (UK) for donating
the HPMC,and Razak Company for
supplying sildenafil powder.
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... One of the most widely used treatments of ED is sildenafil citrate, a selective guanosine inhibitor, which has shown to be effective in treatment of erectile dysfunction. Despite its undeniable effects, it also has several adverse effects, the most important of which reported in various studies is visual impairment (12). In fact, synthetic drugs with favorable results in treatment of ED have adverse effects, indicating the necessity of alternative drugs with fewer complications (13). ...
... The first trial by Kamenov et al. (2017) showed that the International index of erectile function and its dimensions) (IIEF) score significantly improved in Prior to the treatment, the mean IIEF was 13.2 (minimum 5-21 maximum) in the intervention group and the mean IIEF was 11.6 (6-21) in the placebo group. After treatment, the mean IIEF was 15.3 (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) in the intervention group and 13.7 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) in the placebo group. Therefore, TT was not more effective than placebo in improving the symptoms of ED (21). ...
... The first trial by Kamenov et al. (2017) showed that the International index of erectile function and its dimensions) (IIEF) score significantly improved in Prior to the treatment, the mean IIEF was 13.2 (minimum 5-21 maximum) in the intervention group and the mean IIEF was 11.6 (6-21) in the placebo group. After treatment, the mean IIEF was 15.3 (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) in the intervention group and 13.7 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) in the placebo group. Therefore, TT was not more effective than placebo in improving the symptoms of ED (21). ...
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... The mechanism of action of sildenafil involves the specific degradation of cyclic guanosine monophosphate (cGMP), resulting in smooth muscle relaxation via the nitric oxide (NO) pathway [1]. Thus, sildenafil citrate is an effective oral treatment for erectile dysfunction and premature ejaculation [2,3]. It is available only in the form of tablets. ...
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... If an exogenous NO donor were administered concurrently with a PDE 5 inhibitor, there would be enhancement of the smooth muscle effects of NO but no cGMP dependent feedback on NO generation, since it does not involve NO generation through nNOS. The reports we have found in the literature on priapism with PDE 5 inhibitors involve either the use of selective PDE 5 inhibitors at a dosage above the recommended level or their use together with other pro-erectile substances by oral or intracavernous administration (Aoyagi et al., 1999;McMahon, 2003;Yonessi and Saeedi, 2005). At least the latter are situations where a negative cGMP-dependent feedback on NO formation might be expected to be bypassed. ...
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Introduction Due to the prevalence of erectile dysfunction and impotence among men in recent years, several pharmacotherapies have been considered for such problems. Systemic drug therapies in the treatment of erectile dysfunction have significant issues, including drug interactions and contraindications in a wide range of diseases, which makes researchers seek to design drugs and dosage forms with fewer side effects, interactions, and contraindications with maintained efficacy. Objectives 5-Phosphodiesterase inhibitors (5-PDEIs or PDE5Is), previously used systemically to treat erectile malfunction, are now appropriate candidates for topical application with considerable potency and fewer complications. Methods We sought to investigate the recent findings on the current subject in order to provide a comprehensive overview of the issue using an extensive literature search to pinpoint the latest scientific reports on this subject. Results In the present review, the function of 5-Phosphodiesterase inhibitors as topical formulations was evaluated with details including formulation type, adsorption, and comparative efficacy in all recent studies as an acceptable alternative therapy to systemic drugs. Conclusions Due to the fact that the influential factors in erectile dysfunction interact with many diseases and delinquent treatments, the use of topical therapeutic agents can be promising in mild to moderate cases. The utilization of 5-PDEIs through novel topical and transdermal drug delivery techniques plays a vital role in improving this effectiveness. Hamzehnejadi M, Tavakoli MR, Abiri A, et al. A Review on Phosphodiesterase-5 Inhibitors as a Topical Therapy for Erectile Dysfunction. Sex Med Rev 2021;XX:XXX–XXX.
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Sildenafil is used to treat erectile dysfunction, and prescription on the NHS is restricted. We are conducting a study of prescription event monitoring for sildenafil in England, the first phase of which investigates possible short term effects in a cohort of about 5000 users. In view of the interest in myocardial infarction as a possible short term side effect1 we report on an analysis of selected cardiovascular events reported in the first phase. Prescription event monitoring has been described elsewhere.2 Patients were identified from NHS prescriptions in England. Simple questionnaires were posted to the prescribing general practitioners about five months after the first prescription. These forms requested reporting of events after the drug had been prescribed. An “event” was any new diagnosis, any reason for referral to a consultant or admission to hospital, unexpected deterioration (or improvement) in a …
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Sildenafil citrate is the first orally active therapy proved to be effective and safe treatment for erectile dysfunction (ED). Because men with cardiovascular disease are at increased risk of developing ED, and because ED and cardiovascular disease share important risk factors, attention has focused recently on the use of sildenafil in these men. When used in combination with nitroglycerin and other nitric oxide (NO) donors, sildenafil may potentiate major drops in blood pressure. Use of nitrate antianginal agents are an absolute contraindication to sildenafil use. In normotensive men and in men receiving antihypertensive medications evaluated in Phase II/III clinical trials, sildenafil use at the recommended doses (25-100 mg 1 hour before sexual intercourse and no more than once daily) was associated with modest, transient reductions in blood pressure and negligible effects on heart rate. In a more recent study, sildenafil was well tolerated in patients receiving antihypertensive medications and was not associated with major decreases in blood pressure. From the time of its approval in the United States in March 1998 through mid-November 1998, with approximately 6 million prescriptions written, 130 deaths were reported by the US Food and Drug Administration (FDA). Seventy-seven of the men who died had documented cardiovascular events. Sixteen men took or were administered nitroglycerin or an organic nitrate; 3 others had nitroglycerin in their possession. Physician prescribing guidelines issued by the American College of Cardiology/American Heart Association (ACC/AHA) recommend caution when prescribing sildenafil to men with certain cardiovascular conditions, liver or kidney disease, and to those taking medications that may prolong sildenafil's half-life (e.g., erythromycin or cimetidine). Those with known or suspected coronary artery disease may benefit from an exercise test to determine whether resumption of sexual activity with use of sildenafil is likely to be associated with an increased risk of myocardial ischemia.
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Sildenafil citrate is the first oral agent approved for the treatment of erectile dysfunction (ED); other oral agents are in the process of development. Because the mechanism of action of many of these agents involves vasodilation, there is a potential for interaction with the cardiovascular system. Sildenafil inhibits phosphodiesterase-5 (PDE-5) which is found in the corpus cavernosum and in the systemic vasculature. Sildenafil causes a mild decrease in systemic arterial pressure ( approximately -8/-5.5 mm Hg); it causes a synergistic and often major decrease in systemic arterial pressure in the presence of organic nitrates (nitric oxide donors). Sildenafil is therefore contraindicated in patients taking organic nitrates. A review was made of clinical trials in populations of men with (1) erectile dysfunction; (2) chronic stable ischemic heart disease and erectile dysfunction; and (3) hypertension and erectile dysfunction. This review showed that sildenafil was effective and not associated with an increase in serious cardiovascular adverse events, myocardial infarction (MI), or death compared with placebo. Although there have been spontaneous reports of death among men using sildenafil, there are limitations to spontaneous-event reporting. In addition. the numbers of such reports are well below the expected numbers of deaths when considering the number of men who have received prescriptions for sildenafil and their age and cardiovascular risk factor profile. Because there is a small but finite risk of having a cardiac event with sexual activity, physicians should discuss with their cardiac patients the risks of sexual activity before prescribing any treatment for ED. In addition, they should evaluate their patients' cardiac status when considering the safety of administering any ED treatment that may have systemic vasodilatory properties and can potentially lower blood pressure. In some cases, exercise treadmill testing may be warranted to determine whether ED patients with coronary artery disease can achieve the physiologic workload (4-6 metabolic equivalents) associated with sexual intercourse.
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Sildenafil citrate (Viagra) has been shown to be an effective treatment for erectile dysfunction. Initial studies reported a high tolerability and low incidence of certain characteristic adverse reactions. We sought to evaluate the incidence of side effects of sildenafil citrate, independent of industry support and constraints, utilizing a heterogeneous cohort of patients from a university-based practice. A prospective, open-label, flexible-dose study of 256 patients treated with sildenafil citrate for erectile dysfunction was performed at a single institution. The patients were questioned explicitly about the occurrence of headache, flushing, dyspepsia, nasal congestion, visual changes, and other side effects. The adverse reactions most commonly observed were flushing (30.8%), headache (25. 4%), nasal congestion (18.7%), and heartburn (10.5%). All events were short lived and mild in nature. In the present study, 31.6% of patients experienced one or more adverse events. However, no one withdrew from the study because of the severity of these events. There was a significant association between higher doses and the occurrence of side effects. The incidence of adverse events attributable to sildenafil citrate may be higher than initially reported, but an explanation may be the methodology of data collection and the industry-independent nature of this study. The side-effect profile is dose related and mild. Sildenafil citrate remains a safe and well-tolerated treatment for erectile dysfunction.
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Sildenafil (Viagra) has been linked to 240 deaths (128 verified, 112 unverified) reported to the Food and Drug Administration (FDA) during 7.5 months of availability, and to 522 reported deaths after 13 months of availability. To date, no updated information about FDA-reported deaths has emerged, and no comparative analyses have been published. To compare the mortality rates between sildenafil and injectable alprostadil, both of which are used exclusively for treating erectile dysfunction. A comparison of the number of deaths per filled prescriptions reported to the FDA involving sildenafil and injectable alprostadil was undertaken to perhaps provide further insight into this issue. Materials included FDA statements on sildenafil adverse event reports to the FDA involving sildenafil and injectable alprostadil, and data on prescriptions filled for sildenafil and injectable alprostadil. The number of deaths per prescriptions filled reported in association with sildenafil was significantly greater (5.15-6.28 times) than in association with injectable alprostadil. Previous explanations for sildenafil-associated deaths have been based on the expected attrition within the population of men with erectile dysfunction and its commonly associated disorders, the physiologic stress of renewed sexual activity, and a pharmacologic effect of sildenafil. The results of this analysis may indicate that a pharmacologic effect of sidenafil is responsible for these deaths. However, other factors may also explain these findings: a greater frequency of reporting of sildenafil-associated events by physicians, a difference in the populations using these two drugs, or the number of prescriptions filled may not accurately reflect actual exposure. Further study should be undertaken to clarify the issues associated with sildenafil-related deaths. In the meantime, reasonable precautions might be considered in prescribing sildenafil, such as initiating treatment with a low test dose of sildenafil.
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A flow injection analysis (FIA) of sildenafil citrate (SLD) using UV detection is described in this study. The best solvent system was found to be consisting of 0.2 M phosphate buffer at pH 8 having 10% MeOH. A flow rate of 1 ml. min(-1) was pumped and active material was detected at 292 nm. The calibration equation was linear in the range of 1x10(-6)-5x10(-6) M. Limit of detection (LOD) and limit of quantitation (LOQ) were calculated to be 3x10(-7) and 8.9x10(-7) M with a R.S.D. 1.9 and 0.6% (n=7), respectively. The proposed method was applied to the determination of SLD in VIAGRA tablet, containing 50 mg active material. The results were compared with those obtained from UV-Spectrophotometry. The results showed that there is a good agreement between FIA method and the UV-Spectrophotometry. The validation studies were realised by the related applications and the results were evaluated statistically. According to the results, insignificant difference was observed between the methods.
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Erectile dysfunction (ED) is a common problem with a multifactorial aetiology. The treatment of ED has been revolutionised by the introduction of intracavernosal injections some two decades ago. However, the recent development of the orally-administered drug sildenafil (Viagra) has had a major impact on the treatment of ED. We discuss the trials with sildenafil with special reference to cardiovascular risk factors associated with ED.