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On study days, eye examinations were done in the following order (time needed per examination in brackets; reference is also provided in study flowchart, ): Humphrey 30-2 visual field test (20 minutes) Humphrey 30-2 visual field test (20 minutes) Administration of eye drops for mydriasis and waiting period (30 minutes) Administration of eye drops for mydriasis and waiting period (30 minutes) The color discrimination error score of this test was the primary variable for the assessment of visual function.
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Total error score was calculated based on the test results for the individual caps. In addition, partial scores (error lines 1–4) were calculated for each of the four boxes of the Farnsworth–Munsell 100 test. According to published data square root of error scores were used to reach a better approximation of the normal distribution.Citation16 Scotopic and photopic ERG measurements were performed according to International Society for Clinical Electrophysiology of Vision (ISCEV) standards.Citation17 ERGs were recorded by Amplaid MK15 evoked potential system (Amplaid USA Inc., Rolling Meadows, IL, USA) connected to corneal jet electrodes.
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Quantitative target variables were subjected to an analysis of covariance (ANCOVA) with the factors: treatment, period, subject, sequence, time, and the interactions period*time, treatment*time and the baseline value as a covariate. BAY 38–9456 40 mg (vardenafil hydrochloride) was generally well tolerated. Adverse events were more common in subjects receiving active BAY 38–9456 (vardenafil hydrochloride) when compared to those receiving placebo. The most frequently reported adverse event in each treatment group was “headache”. The intensity of all adverse events was reported as “mild” or “moderate” and the relationship to study drug was “possible” in all cases.
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All adverse events had resolved by the end of the study while there was no evidence for a serious adverse event at any time (). The color discrimination error score of the Farnsworth– Munsell test was the primary variable for the assessment of the visual function. The most pronounced differences between the two treatment groups were observed for total error score 1 and 6 hours after drug administration, and for error score online levitra pharmacy lines 3, and 4 one hour after drug administration, indicating an impairment of color discrimination particularly in representing color vision of blue/green and purple. Minor differences were still present after 6 hours affecting error score lines 1, 3, and 4. There were no differences after 24 hours between active and placebo ( and ). Following dark adaptation of 30 minutes ERGs were recorded according to single flash stimulation with constant luminance stimulus (cds/m2) of 2.4 cds/m2 (no background illumination) and 5.0 cds/m2 (additional background illumination of 20 cd/m2). Concentration measurements of BAY 38–7268 and BAY 44–5576 in plasma indicated subject compliance. Moreover, urine probes were taken at baseline to detect possible drug abuse (opiates, amphetamines, barbiturates, cannabis, benzodiazepines, cocaine-metabolites) which would have led to exclusion of the subject. The statistical evaluation was performed using SAS software package (version 6; SAS Institute Inc., Cary, NC, USA). All data were listed and trial summary tables were provided. Exploratory statistical tests were performed to compare the visual function tests following BAY 38–9456 and placebo, respectively. Quantitative target variables were subjected to an analysis of covariance (ANCOVA) with the factors: treatment, period, subject, sequence, time, and the interactions period*time, treatment*time and the baseline value as a covariate. BAY 38–9456 40 mg (vardenafil hydrochloride) was generally well tolerated. Adverse events were more common in subjects receiving active BAY 38–9456 (vardenafil hydrochloride) when compared to those receiving placebo. The most frequently reported adverse event in each treatment group was “headache”. The intensity of all adverse events was reported as “mild” or “moderate” and the relationship to study drug was “possible” in all cases. All adverse events had resolved by the end of the study while there was no evidence for a serious adverse event at any time ().
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The color discrimination error score of the Farnsworth– Munsell test was the primary variable for the assessment of the visual function. The most pronounced differences between the two treatment groups were observed for total error score 1 and 6 hours after drug administration, and for error score online levitra pharmacy lines 3, and 4 one hour after drug administration, indicating an impairment of color discrimination particularly in representing color vision of blue/green and purple.
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In comparison to screening ERG with b-wave amplitude of 225±91 µV (2.4 cds/m2), in ERG after 1 hour 20 minutes with active treatment b-wave amplitude was reduced by 15% compared to a reduction of 10% observed with placebo. While there was no relevant difference in b-wave amplitude between the treatment groups after 6 hours 20 minutes, there were again differences between active and placebo after 24 hours (). Compared to a baseline value of 92±41 µV (5 cds/m2), b-wave amplitude was reduced by 27% after 1 hour 20 minutes with active treatment while placebo group showed a reduction of 12%. A less prominent amplitude reduction was still present after 6 hours 20 minutes with active treatment. At 24 hours, the amplitude had nearly returned to baseline values; however, there was still a difference between active and placebo after 24 hours ().
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The ANCOVA for the observations of a-wave and b-wave revealed a significant influence of the factor treatment on the amplitude of the a-wave, 2.4 cds/m2 (P=0.0152), as well as on the amplitude of the b-wave, 2.4 cds/m2 (P=0.0302) and 5 cds/m2 (P=0.0028). Moreover, a significant influence of time on the amplitude of the b-wave, 2.4 cds/m2 (P=0.0170) and 5 cds/m2 (P=0.0020), was observed. The b-wave amplitude increased with time after administration of active treatment or placebo. There were no relevant differences between active and placebo in regard to ERG latency for neither a-wave nor b-wave at any time up to 24 hours after drug administration. Other ophthalmological examinations like visual acuity, refraction, intraocular pressure, Humphrey 30-2 visual field test, Amsler grid field test, slit-lamp, and funduscopy did not reveal any significant differences between the two treatment groups (Supplementary materials). Minor differences were still present after 6 hours affecting error score lines 1, 3, and 4.
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It is known from in-vitro studies that PDE-6, which is found levitra for ed predominantly in retinal photoreceptors, is a key enzyme in the phototransduction cascade.Citation15 PDE-6 is required for the transformation of light into electrical signals. For this reason, retinal effects of PDE inhibitors are not unexpected. PDE-6 is also weakly inhibited by PDE-5 inhibitors and high plasma concentrations of the latter can be expected to inhibit the phototransduction process in retinal photoreceptors.Citation10 Many investigations have been performed on ocular side effects of PDE-5 inhibitors, especially for the use of its best-known representative sildenafil citrate.Citation18–Citation22 In regard to visual function, visual acuity, visual fields, and contrast sensitivity remained unaffected while a temporary impairment of color discrimination represents a definitive effect. Studies on retinal function due to ingestion of sildenafil showed temporary alterations of ERG and color vision correlating with peak plasma concentrations of sildenafil.Citation13,Citation14 Accordingly, in our double-blind, crossover study on ocular side effects of vardenafil hydrochloride, the most pronounced differences between active treatment and placebo in the Farnsworth–Munsell 100 test were observed for total error score 1 and 6 hours after drug administration. The findings correlated with BAY 38–7268 and its active metabolite’s plasma concentrations.
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There were no differences after 24 hours between active and placebo. The data indicate a mild and transient impairment of color discrimination particularly in representing color vision of blue/green and purple and go along with the results of investigations performed on ocular side effects of sildenafil revealing similar color vision alterations which resolve within 24 hours in correlation with plasma concentrations of the drug.Citation9,Citation11,Citation18 Moreover, ERG measurements showed reductions of the b-wave amplitude with no relevant effects on a-wave amplitude which predominantly recovered after 24 hours. There were no relevant differences between active and placebo in regard to ERG latency at any time up to 24 hours following drug administration. Studies on retinal function after sildenafil administration show a complete recovery of all ERG parameters within 24 hours.Citation9,Citation13 However, as we found a mild reduction of the b-wave amplitude even 24 hours after ingestion of vardenafil our study design could not deliver data on detecting a more precise point in time for complete recovery. Because all these studies were performed in healthy subjects there is little evidence on ocular side effects of PDE-5 inhibitors in patients with preexisting ocular pathologies. There were no differences after 24 hours between active and placebo ( and ). In comparison to screening ERG with b-wave amplitude of 225±91 µV (2.4 cds/m2), in ERG after 1 hour 20 minutes with active treatment b-wave amplitude was reduced by 15% compared to a reduction of 10% observed with placebo. While there was no relevant difference in b-wave amplitude between the treatment groups after 6 hours 20 minutes, there were again differences between active and placebo after 24 hours ().
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Compared to a baseline value of 92±41 µV (5 cds/m2), b-wave amplitude was reduced by 27% after 1 hour 20 minutes with active treatment while placebo group showed a reduction of 12%.
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On study days, eye examinations were done in the following order (time needed per examination in brackets; reference is also provided in study flowchart, ): Humphrey 30-2 visual field test (20 minutes) Humphrey 30-2 visual field test (20 minutes) Administration of eye drops for mydriasis and waiting period (30 minutes) Administration of eye drops for mydriasis and waiting period (30 minutes) The color discrimination error score of this test was the primary variable for the assessment of visual function. Total error score was calculated based on the test results for the individual caps. In addition, partial scores (error lines 1–4) were calculated for each of the four boxes of the Farnsworth–Munsell 100 test. According to published data square root of error scores were used to reach a better approximation of the normal distribution.Citation16 Scotopic and photopic ERG measurements were performed according to International Society for Clinical Electrophysiology of Vision (ISCEV) standards.Citation17 ERGs were recorded by Amplaid MK15 evoked potential system (Amplaid USA Inc., Rolling Meadows, IL, USA) connected to corneal jet electrodes. Following dark adaptation of 30 minutes ERGs were recorded according to single flash stimulation with constant luminance stimulus (cds/m2) of 2.4 cds/m2 (no background illumination) and 5.0 cds/m2 (additional background illumination of 20 cd/m2).
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Concentration measurements of BAY 38–7268 and BAY 44–5576 in plasma indicated subject compliance. Moreover, urine probes were taken at baseline to detect possible drug abuse (opiates, amphetamines, barbiturates, cannabis, benzodiazepines, cocaine-metabolites) which would have led to exclusion of the subject. The statistical evaluation was performed using SAS software package (version 6; SAS Institute Inc., Cary, NC, USA). All data were listed and trial summary tables were provided. Exploratory statistical tests were performed to compare the visual function tests following BAY 38–9456 and placebo, respectively. A less prominent amplitude reduction was still present after 6 hours 20 minutes with active treatment. At 24 hours, the amplitude had nearly returned to baseline values; however, there was still a difference between active and placebo after 24 hours (). The ANCOVA for the observations of a-wave and b-wave revealed a significant influence of the factor treatment on the amplitude of the a-wave, 2.4 cds/m2 (P=0.0152), as well as on the amplitude of the b-wave, 2.4 cds/m2 (P=0.0302) and 5 cds/m2 (P=0.0028). Moreover, a significant influence of time on the amplitude of the b-wave, 2.4 cds/m2 (P=0.0170) and 5 cds/m2 (P=0.0020), was observed. The b-wave amplitude increased with time after administration of active treatment or placebo.
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There were no relevant differences between active and placebo in regard to ERG latency for neither a-wave nor b-wave at any time up to 24 hours after drug administration. Other ophthalmological examinations like visual acuity, refraction, intraocular pressure, Humphrey 30-2 visual field test, Amsler grid field test, slit-lamp, and funduscopy did not reveal any significant differences between the two treatment groups (Supplementary materials). It is known from in-vitro studies that PDE-6, which is found levitra for ed predominantly in retinal photoreceptors, is a key enzyme in the phototransduction cascade.Citation15 PDE-6 is required for the transformation of light into electrical signals. For this reason, retinal effects of PDE inhibitors are not unexpected.
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In our study, visual acuity, refraction, intraocular pressure, Humphrey 30-2 visual field test, Amsler grid field test, slit-lamp, and funduscopy did not reveal any significant differences between the two treatment groups. This goes along with studies investigating ocular side effects of sildenafil in patients suffering from open-angle glaucoma or age-related macular degeneration where these parameters remained unaffected as well.Citation21,Citation23 In animal experiments, knockout mice with retinal degeneration support the assumption that administration of PDE-5 inhibitors in patients with retinal degenerations may lead to more pronounced effects on retinal function. Meanwhile, recovery of electrophysiological alterations took about two weeks in carrier mice compared to a recovery period of two days in wildtype mice.Citation24 Up to now, it is unclear whether administration of PDE-5 inhibitors in human subjects would show more distinctive side effects on retinal function as well. Future investigations in patients with retinal degenerations may give an answer.Citation24,Citation25 In conclusion, BAY 38–9456 40 mg (vardenafil hydrochloride) was generally well tolerated. As expected, adverse events were more common in subjects receiving active BAY 38–9456 (vardenafil hydrochloride) compared to those receiving placebo.
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Our study shows comparable results to studies on sildenafil and confirms a good tolerability of vardenafil in regard to ocular side effects. The authors report no conflicts of interest in this work. MorelandRBGoldsteinITraishASildenafil, a novel inhibitor of phosphodiesterase type 5 in human corpus cavernosum smooth muscle cellsLife Sci19986220PL309PL318 BoolellMAllenMJBallardSASildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunctionInt J Impot Res19968247528858389 BallardSAGingellCJTangKTurnerLAPriceMENaylorAMEffects of sildenafil on the relaxation of human corpus cavernosum tissue in vitro and on the activities of cyclic nucleotide phosphodi-esterase isozymesJ Urol19981596216421719598563 PorstHRosenRPadma-NathanHThe efficacy and tolerability of vardenafil, a new, oral, selective phosphodiesterase type 5 inhibitor, in patients with erectile dysfunction: the first at-home clinical trialInt J Impot Res200113419219911494074 StarkSSachseRLiedlTVardenafil increases penile rigidity and tumescence in men with erectile dysfunction after a single oral doseEur Urol200140218119011528196 KlotzTSachseRHeidrichAVardenafil increases penile rigidity and tumescence in erectile dysfunction patients: a RigiScan and pharmacokinetic studyWorld J Urol2001191323911289568 HellstromWJGittelmanMKarlinGVardenafil for treatment of men with erectile dysfunction: efficacy and safety in a randomized, double-blind, placebo-controlled trialJ Androl200223676377112399521 KeatingGMScottLJVardenafil: a review of its use in erectile dysfunctionDrugs200363232673270314636086 ZrennerENo cause for alarm over retinal side-effects of sildenafilLancet19993539150340341 LuuJKChappelowAVMcculleyTJMarmorMFAcute effects of sildenafil on the electroretinogram and multifocal electroretinogramAm J Ophthalmol2001132338839411530053 GabrieliCBRegineFVingoloEMRispoliEFabbriAIsidoriASubjective visual halos after sildenafil (Viagra) administration: Electroretinographic evaluationOphthalmology2001108587788111320016 LatiesAZrennerEViagraZEViagra (sildenafil citrate) and ophthalmologyProg Retin Eye Res200221548550612207947 JägleHJägleCSéreyLVisual short-term effects of Viagra: double-blind study in healthy young subjectsAm J Ophthalmol2004137584284915126148 BeavoJACyclic nucleotide phosphodiesterases: functional implications of multiple isoformsPhysiol Rev19957547257487480160 KinnearPRProposals for scoring and assessing the 100-hue testVision Res19701054234335312357 BrigellMBachMBarberCKawasakiKKooijmanAGuidelines for calibration of stimulus and recording parameters used in clinical electrophysiology of vision. PDE-6 is also weakly inhibited by PDE-5 inhibitors and high plasma concentrations of the latter can be expected to inhibit the phototransduction process in retinal photoreceptors.Citation10 Many investigations have been performed on ocular side effects of PDE-5 inhibitors, especially for the use of its best-known representative sildenafil citrate.Citation18–Citation22 In regard to visual function, visual acuity, visual fields, and contrast sensitivity remained unaffected while a temporary impairment of color discrimination represents a definitive effect. Studies on retinal function due to ingestion of sildenafil showed temporary alterations of ERG and color vision correlating with peak plasma concentrations of sildenafil.Citation13,Citation14 Accordingly, in our double-blind, crossover study on ocular side effects of vardenafil hydrochloride, the most pronounced differences between active treatment and placebo in the Farnsworth–Munsell 100 test were observed for total error score 1 and 6 hours after drug administration. The findings correlated with BAY 38–7268 and its active metabolite’s plasma concentrations.
| Side Effect | Severity | Frequency | Additional Notes |
|---|---|---|---|
| Headache | Mild to Moderate | Common | Usually subsides in a few hours |
| Flushing | Mild | Common | Feelings of warmth or redness |
| Dizziness | Mild | Less Common | Avoid driving if affected |
| Nasal Congestion | Mild | Less Common | Temporary nasal stuffiness |
| Back Pain | Mild | Less Common | Usually resolves spontaneously |
There were no differences after 24 hours between active and placebo. The data indicate a mild and transient impairment of color discrimination particularly in representing color vision of blue/green and purple and go along with the results of investigations performed on ocular side effects of sildenafil revealing similar color vision alterations which resolve within 24 hours in correlation with plasma concentrations of the drug.Citation9,Citation11,Citation18 Moreover, ERG measurements showed reductions of the b-wave amplitude with no relevant effects on a-wave amplitude which predominantly recovered after 24 hours.
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There were no relevant differences between active and placebo in regard to ERG latency at any time up to 24 hours following drug administration. Studies on retinal function after sildenafil administration show a complete recovery of all ERG parameters within 24 hours.Citation9,Citation13 However, as we found a mild reduction of the b-wave amplitude even 24 hours after ingestion of vardenafil our study design could not deliver data on detecting a more precise point in time for complete recovery. Because all these studies were performed in healthy subjects there is little evidence on ocular side effects of PDE-5 inhibitors in patients with preexisting ocular pathologies. In our study, visual acuity, refraction, intraocular pressure, Humphrey 30-2 visual field test, Amsler grid field test, slit-lamp, and funduscopy did not reveal any significant differences between the two treatment groups. This goes along with studies investigating ocular side effects of sildenafil in patients suffering from open-angle glaucoma or age-related macular degeneration where these parameters remained unaffected as well.Citation21,Citation23 In animal experiments, knockout mice with retinal degeneration support the assumption that administration of PDE-5 inhibitors in patients with retinal degenerations may lead to more pronounced effects on retinal function.
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Meanwhile, recovery of electrophysiological alterations took about two weeks in carrier mice compared to a recovery period of two days in wildtype mice.Citation24 Up to now, it is unclear whether administration of PDE-5 inhibitors in human subjects would show more distinctive side effects on retinal function as well. Future investigations in patients with retinal degenerations may give an answer.Citation24,Citation25 In conclusion, BAY 38–9456 40 mg (vardenafil hydrochloride) was generally well tolerated.
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As expected, adverse events were more common in subjects receiving active BAY 38–9456 (vardenafil hydrochloride) compared to those receiving placebo. Our study shows comparable results to studies on sildenafil and confirms a good tolerability of vardenafil in regard to ocular side effects.
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The authors report no conflicts of interest in this work. MorelandRBGoldsteinITraishASildenafil, a novel inhibitor of phosphodiesterase type 5 in human corpus cavernosum smooth muscle cellsLife Sci19986220PL309PL318 BoolellMAllenMJBallardSASildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunctionInt J Impot Res19968247528858389 BallardSAGingellCJTangKTurnerLAPriceMENaylorAMEffects of sildenafil on the relaxation of human corpus cavernosum tissue in vitro and on the activities of cyclic nucleotide phosphodi-esterase isozymesJ Urol19981596216421719598563 PorstHRosenRPadma-NathanHThe efficacy and tolerability of vardenafil, a new, oral, selective phosphodiesterase type 5 inhibitor, in patients with erectile dysfunction: the first at-home clinical trialInt J Impot Res200113419219911494074 StarkSSachseRLiedlTVardenafil increases penile rigidity and tumescence in men with erectile dysfunction after a single oral doseEur Urol200140218119011528196 KlotzTSachseRHeidrichAVardenafil increases penile rigidity and tumescence in erectile dysfunction patients: a RigiScan and pharmacokinetic studyWorld J Urol2001191323911289568 HellstromWJGittelmanMKarlinGVardenafil for treatment of men with erectile dysfunction: efficacy and safety in a randomized, double-blind, placebo-controlled trialJ Androl200223676377112399521 KeatingGMScottLJVardenafil: a review of its use in erectile dysfunctionDrugs200363232673270314636086 ZrennerENo cause for alarm over retinal side-effects of sildenafilLancet19993539150340341 LuuJKChappelowAVMcculleyTJMarmorMFAcute effects of sildenafil on the electroretinogram and multifocal electroretinogramAm J Ophthalmol2001132338839411530053 GabrieliCBRegineFVingoloEMRispoliEFabbriAIsidoriASubjective visual halos after sildenafil (Viagra) administration: Electroretinographic evaluationOphthalmology2001108587788111320016 LatiesAZrennerEViagraZEViagra (sildenafil citrate) and ophthalmologyProg Retin Eye Res200221548550612207947 JägleHJägleCSéreyLVisual short-term effects of Viagra: double-blind study in healthy young subjectsAm J Ophthalmol2004137584284915126148 BeavoJACyclic nucleotide phosphodiesterases: functional implications of multiple isoformsPhysiol Rev19957547257487480160 KinnearPRProposals for scoring and assessing the 100-hue testVision Res19701054234335312357 BrigellMBachMBarberCKawasakiKKooijmanAGuidelines for calibration of stimulus and recording parameters used in clinical electrophysiology of vision.
