Download EVALUATION OF ERECTILE RESPONSE TO SIlDENAFIL

EVALUATION OF ERECTILE RESPONSE TO SIlDENAFIL
THROUGH SEXUAL VISUAL STIMULATION IN ERECTILE
DISFUNCTION
Molo M.T., Ristori S., Perozzo P., Vighetti S., Cantafio P.
CE.R.NE. Centro di Ricerche in Neuroscienze
- Turin, Italy
SUMMARY
The aim of this work is to evaluate the erectile response in a sample of patients treated with
Sildenafil. To do this, 20 people aged between 20 and 50 years with a diagnosis of erectile
disfunction were selected. Each erectile response to sexual visual stimulation (SVS) was recorded
using Rigiscan, and both neurovegetative and neurophysiological parameters were monitored.
The erectile responses were studied during two different phases : the first one in basal conditions,
and the second one after adminastration of 50 mg. of Sildenafil by mouth. Using SVS we managed
to obtain an objective evaluation of the erectile response with this pharmacological treatment,
which, as it is well known, requires an adequate stimulation at the same time. The SVS, widely
tested on a normal population, in this case proves to be a proper stimulation.
INTRODUCTION
The Sildenafil revolution is basically due to the fact that it represents the first oral drug
often effective in treating a disease so diffused and rich of emotional implications such as the
Erectile Disfuction ; furthermore it shows mild collateral effects and few absolute
contraindications.
As usual the market launch of the molecule came after a huge number of studies carried
out to assess its clinical effectiveness and its tolerance in practically any kind of Erectile
Disfunction .
From a review of these works it can be argued that :
1.
Sildenafil is effective in doses between 25 and 100 mg, and it shows dose-dependent results
not improving with doses higher than 100 mg
1
2.
Best effects are observed when taken approximately one hour before the sexual performance
3.
Effectiveness
varies
through
the
kind
of
pathology
underlying
the
Erectile
Disfunction (psychogenic 90%)
4.
The drug-induced erection lasts up to four hours
5.
Collateral effects both in the short and in the long run are the same, however mild and rare
(cephalea 16%, flush 10%, dyspepsia 7%, visual alterations 3%, nasal congestion 4%).
Almost all the results above summarized were obtained in studies which assessed the
response through subjective parameters (IIEF, questionnaires investigating the size of the erectile
response, the number of sexual intercourse, the level of satisfaction of the subject and of his
partner). These results, obtained via self evaluation, have been confirmed through objective
methodologies (Rigiscan).
It is well known that “a drug can not substitute an erogenous stimulus, neither can it turn
in erogenous a stimulus that is not so” (Drug Evaluation and Inspection Department of Health
Ministery). Thus a strict survey on Sildenafil’s effectiveness, besides the use of Rigiscan to
measure the erectile response, requires, after taking the drug, an adequate erogenous stimulus on
the subject.
In this research sexual visual stimulation (SVS) has been proposed as an adequate erogenous
stimulus : it is a diagnostic technique not thoroughly standardized, quite spread and already used
by some researchers (Boolell,1998,1999) during studies on sildenafil.
In detail, our study aims to :
confirm on a sample of italian population the general data about response to
sildenafil;
assess in which cases the use of sildenafil can be associated to SVS as a not-invasive
technique effective and adeguate in sexological diagnosis.
We also intended to determine possible Sildenafil effects on the Central Nervous System
and on the Autonomic Nervous System using Brain Mapping and monitoring some
neurovegetative parameters.
Brain Mapping consists in a quantitative EEG rappresented by topographic maps of the
brain.
This method is used to better characterize and correctly classify many disorders affecting human
brain functions.
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MATERIALS AND METHODS
The sample consists of 20 male subjects aged between 20 and 50 years, and 34,6 years
old on average . Before the partecipation to the research, each subject was given the International
Index of Erectile Function (IIEF-5), a shorter version of the IIEF questionnaire used in many
previous clinical studies carried out using Sildenafil and placebo. It is an instrument less long and
complex than the IIEF, though as much sensible and specific in diagnosing Erectile Disfunction
(that is with an high rate of true positive and a low rate of false negative). It is composed of five
questions : four of them analyse the erectile function and the last the sexual satisfaction
(psychological factor). All the subjects underwent an accurate assessment and spefic physical
tests, excluding an hormonal or circulatory etiology
Before the experimental session each subject had to answer a questionnaire which is
composed of ten questions about his erotic imagination, aimed to assess his willingness to watch
explicit erotic stimuli and his possible preferences for specific sexual behaviours.
Our survey is organized in two phases during which the erectile response is monitored :
in the first phase the erectile response was observed in basal conditions,that is without the use of
Sildenafil and during the second one, one month, later, approximately 60 minutes after taking 50
mg of Sildenafil by mouth.
Each subject during both phases underwent sexual visual stimulation and his erectile
response was recorded using Dacomed Rigiscan Plus Rigidity Assessment System in order to
obtain an objective mesure of erection. At the same time we monitored electric cerebral activity
by Brain Mapping and the following neurovegetative parameters: heart rate, breathing and skin
sympathetic response.
The erectile response assessment using Rigiscan is carried out putting two latex rings at
the poenis base and at the prepuce: inside the two rings a transducer records in real time rigidity
and tumescence changes ; data are send to and are processed by a Pentium 90 with 8 Megabite
RAM memory and 128 Hz sampling.
Once fixed the baseline, for which 10 to 15 minutes are necessary (during this time the
subject is asked to stay relaxed with closed eyes), the visual stimulation begins using hard-core
stimuli. In order to avoid to get accustomed to the stimulus, each subject watched two different
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hard-core movies, one for each session. The videos lasted respectively 5 and 3 minutes, they were
edited with similar sequencies and they were watched randomly.
The whole session lasted from 20 to 30 minutes approximately, depending on the video,
with the following sequence :
1- hard-core video showing a vaginal coitus;
2- landscapes scenes (neutral stimulus);
3- hard-core video showing an oral coitus;
4- landscapes scenes;
5- hard-core video showing an anal coitus;
6- landscapes scenes.
Each hard-core video was edited with landscape scenes intervals all equally lasting, in
order to reduce to the minimum the possible summation effects of the stimuli from one hard-core
scene to the other, and so serving as a running baseline.
All subjects were also submitted to brain mapping recorder during SVS sessions and they
were prepared with 16 EEG recording leads affixed at the frontal, temporal, parietal and occipital
loci for both hemispheres, with linked common ear reference. Epochs of two seconds of digitized
EEG data underwent Fast Fourier Trasformation analysis according to the following band power
spectrum densities: delta (0.5 – 3.5 Hz), theta (4 – 7.5 Hz), alpha (8 – 12.5 Hz), beta (13 – 30 Hz).
RESULTS
We considered as valid erectile episodes those when Rigiscan recorded a rigidity of at
least 60%.
The results were the following (fig.1) :
10 patients (50% of the sample) did not show any erectile response during SVS without the use of
Sildenafil, while erectile episodes, from one to three depending on the subject, were recorded
during the Sildenafil session. In six patients (30% of the sample) one erectile episode was
observed during SVS without the use of Sildenafil and from two to three after Sildenafil ; three
patients (15% of the sample) did not show any erectile response in neither session. Finally, one
patient had one erectile response without Sildenafil. and not any taking it.
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Summary of Valid Erectile Responses
SVS
Basal
Conditions
+
+
10 subjects (50%)
6 subjects (30%)
3 subjects (15%)
1 subject (5%)
+ = presence of valid erectile response
- = absence of valid erectile response
SVS
+50 mg
SILDENAFIL
+
+
Fig. 1
In fig.2 we can see an example of rigidometric plots of a subject not responding to basal
SVS and responding to SVS plus Sildenafil.
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This means that Sildenafil induced a positive response in 16 patients with Erectile Deficit,
up to 80% of the entire sample : this result is reasonably similar to the percentage of therapeutic
successes referred in literature about psychogenic cases (90-95%).
After SVS plus Sildenafil session, some subjects expressed their opinion about the
experience and, in general, there was agreement between verbal report and Rigiscan result. Two
subjects refered an excitement sensation after SVS with Sildenafil session, even if they didn’t show
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a significative response during both conditions. Maybe, emotion and cognitive aspects related to
Sildenafil assumption, could explain these data.
Brain mapping data were analyzed by Student t-Test and Fisher Test and some
differences between the pharmacological session and the basal conditions were found: an increase
of slow waves (theta and alpha 1 rithms) during SVS basal condition and an increase of fast waves
(alpha 2 and beta rithms) during SVS with Sildenafil. This result shows a desynchronization of
cerebral electrical activity with greater attention in SVS with Sildenafil consumption.
Neurovegetative parameters (fig.3) showed a significative increase of heart rate, only
during SVS with Sildenafil condition. No significative differences were found on breathing and
skin sympathetic response between the two conditions.
Means of neurovegetative parameters
100
80
60
40
20
0
*
SVS +
SILDENAFIL
BASAL SVS
EKG
BR
SSR
EKG = heart rate
BR=breathing
SSR=Skin Sympathetic Response
* = 16,7 P<0,01
Fig. 3
DISCUSSION AND CONCLUSIONS
The satisfactory clinical response to sildenafil by subjects suffering by Erectile
Disfunction is confirmed.
The unsuccesful cases can be attributed partially to experimental conditions, possibly
unconfortable for the patient (setting of penis rings and of electrodes), while in some subjects it
can be due to the fact that some scenes were disliked (explicitly recognized in one case).
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Sexual Visual Stimulation was able by itself to cause valid erectile responses in some
patients.
Erection assessment measuring rigidity during SVS after Sildenafil can be used as a valid
alternative to SVS with FIC for patients refusing intracavernous injection and who accept
watching an erotic movie. In case of no erection, more invasive exames have to be performed
before making a diagnosis of Psychogenic Erectile Disfunction.
Neurophysiological data support the validity of using SVS with Sildenafil in subjects
suffering by erectile disorder.
Being confirmed both SVS test validity as an adequate sexual stimulus to elicit an erectile
response after Sildenafil, and Sildenafil’s diagnostic - therapeutic effectiveness even without a
willing partner, these are the remaining limits of the test :
lack of standardization ;
variability of the response under different parameters of culture, religion, ethics ;
it is impossible to fit the test to individual’s needs (that is to show scenes exactly
corresponding to the patient’s erotic preference).
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