Since 2000, several clinical studies have been done on the effectiveness of sildenafil citrate in treating female sexual disorders (FSD).
Clinical trials were conducted on the effectiveness of sildenafil in treating women with FSD caused by spinal cord injuries in the year 2000. The spinal cord injuries affected the sacral cord and spinal segments S2 through S5. Nineteen premenopausal women were recruited to participate in the study, and each received either 50 mg of sildenafil citrate or a placebo on one day and the other medication the following day.
One hour after receiving the drug or placebo, the participants were subjected to two 12 minute sessions of audiovisual stimulation, followed by a 6 minute time period of no stimulation. They then were exposed to a second period of two 12 minute sessions of both manual and audiovisual stimulation.
During these sessions, vaginal pulse amplitude (VPA) was measured using vaginal photoplethysmography. Heart rate and blood pressure were also measured.
During both the visual and manual sessions, the group who took sildenafil had a greater level of VPA than those who took the placebo. Subjective arousal, heart rate, and systolic and diastolic blood pressure readings were also greater among the group who took sildenafil. This study was the first to test how effective sildenafil citrate is for women who are being sexually stimulated. Because the study group was small, additional research is required.
In a following study in 2001, 53 premenopausal women who being treated for sexual arousal disorders participated. None of the women in the group were taking hormone therapy or oral contraceptives and they all reported no problems with sexual desire.
The participants were divided into six groups, and each group took either 25 mg of sildenafil citrate, 50 mg of sildenafil citrate, or a placebo. The medications were administered in different sequences.
For a period of 4 weeks, every participant took the medication one hour prior to sexual intercourse. After 4 weeks, they had a one week break before beginning the next medication. Following the treatment, each participant completed a Personal Experience Questionnaire to evaluate their level of interest, enjoyment, and satisfaction in sex.
Both groups taking sildenafil (either 25 mg or 50 mg) reported an improved overall quality of sex life. They had higher levels of arousal, greater frequency of coitus and orgasm, and a higher level of enjoyment than the group taking the placebo. They also reported an increase in the frequency of arousal, higher levels of satisfaction with coitus, and more sexual fantasies than those taking the placebo.
A further study was conducted in 2002, where 12 premenopausal women in good health participated. None of the women reported problems with FSD. They received either 50 mg of sildenafil citrate or a placebo for one week, and then they received the alternate medication the following week. During the test period, the participants viewed 60 minutes of neutral video, then 30 minutes of erotic video, followed by 15 minutes of neutral video.
The results showed no difference in arousal or vaginal wetness in either group, but those taking the sildenafil had an increase in VPA compared with those taking the placebo. VPA was measured continuously using vaginal photoplethysmography and began 15 minutes before the drug was administered. Vaginal wetness and subjective sexual arousal were measured following each session using a scale of 0 to 4. Because this sample size was small and the women did not have FSD, the usefulness of this study is limited.
In 2003, another study was conducted on 68 premenopausal women with no history of FSD. The study was random, double blind, and placebo-controlled. A questionnaire was given before treatment, after treatments, and after a 2 week period where no medication was given. Each participant received either a 50 mg dose of sildenafil citrate or a placebo, with a two week wash out period between treatments.
The women reported a substantial improvement in arousal, orgasm, and overall enjoyment of sexual intercourse, although they had no increase in desire.
A similar study in 2003 was conducted on 34 postmenopausal women taking estrogen replacement therapy for a minimum period of six months, and had reported a loss, delay or decrease in intensity of orgasm. The women were given either 50 mg sildenafil citrate or a placebo one hour before vibratory stimulation and viewing erotic stimulation. The subjects tested the amount of time required from exposure to erotic materials to completion of orgasm, the intensity of orgasm on a scale of one to seven, and VPA was measured using vaginal photoplethysmography. A questionnaire was given prior to and after viewing the erotic video. The results showed no overall effect on orgasm latency, although women who were had low VPA response showed significant improvement after taking sildenafil.
In a test in 2004, nineteen premenopausal women with Multiple Sclerosis and FSD (experiencing arousal and orgasm difficulties) were given either a dose of 50 mg of sildenafil citrate or a placebo for 12 weeks, and then they were given the alternative drug for the following 12 week period. The women receiving the sildenafil reported an improvement in lubrication and sensation, but no change in orgasm, desire, or quality of life.
In 2006, a study was conducted on 32 premenopausal women suffering from Type 1 diabetes and FSD. The participants received either 100 mg of sildenafil citrate or a placebo for a period of 8 weeks, followed by a 1 week wash out period, and then a further 8 week period on the alternate medication. A questionnaire was administered at the start of each session and during the eight week treatment period. The results showed an improvement in arousal and orgasm, and increased clitoral blood flow.
In 2008, a study was done on the effectiveness of sildenafil in treating FSD problems in women taking antidepressants. Ninety-eight premenopausal women participated in the study, who reported FSD for a minimum of four weeks. They had no previous problems with FSD prior to taking the antidepressants.
They received either 50 mg of sildenafil citrate or a placebo for an 8 week trial period. The women were tested prior to treatment, after 2 weeks, 4 weeks, and at the end of the treatment period. All test scales showed a significant improvement in orgasm with the group who took sildenafil citrate over the group taking the placebo.
In all of these studies, the patients reported mild to moderate side effects. The most frequent negative effects were headaches, flushing, nausea, rhinitis, and visual problems.
Although these studies showed an improvement in clitoral blood flow, further study is required to show which patients will benefit most from sildenafil treatment. The results are inconclusive, as female sexual pleasure is derived from a complex set of biological and psychological factors.