Effects of a Novel Erectogenic Condom on Men and Women’s Sexual Pleasure: Randomized Controlled Trial

ABSTRACT

We tested whether CSD500 (Futura Medical; Guildford, UK), a novel condom containing erectogenic gel designed to increase penile firmness, penile size, and erection duration, results in greater sexual pleasure. In 2017–2020, we randomized heterosexual couples in Thanh Hoa, Vietnam to use CSD500 (N = 248) or standard condoms (N = 252) and followed them up for six months. Women completed the Quality of Sexual Experience (QSE) scale; men completed the QSE, Sexual Experience Questionnaire (SEX-Q), and 11 condom acceptability items. Female participants’ mean age was 32.1 years (SD = 0.24; range 21–46). QSE scores were higher among women (B, 0.12; 95% CI, 0.03–0.21) and men (B, 0.21; 95% CI, 0.08–0.35) in the CSD500 relative to the control arm. SEX-Q scores were higher among men in the CSD500 compared to the control arm (B, 3.22; 95% CI, 1.53–4.91). Higher proportions of men in the CSD500 relative to the control arm reported the condom felt “natural” during sex (68.6% vs. 32.3%; p < .01) and that sex with the condom felt “a lot better” than condomless sex (15.5% vs. 5.3%; p < .01). Compared with standard condoms, CSD500 use was associated with higher reports of sexual pleasure and condom acceptability.

Introduction

Reasons for having sex are diverse, ranging from the desire to procreate, increase social status, ameliorate loneliness or foster intimacy in a relationship to wanting to conform to societal expectations (Meston & Buss, 2007). The pursuit of sexual pleasure, however, is a common motivator for both men and women (Regan & Berscheid, 1999). From an evolutionary perspective, sexual pleasure is an adaptive mechanism that ensures sufficient coital frequency for the survival of the human species (Esch & Stefano, 2005). Sexual pleasure also can be viewed as a human right (Giami, 2015) that is inextricably linked to sexual health. According to the World Health Organization (2006), “ … the possibility of having pleasurable … sexual experiences … ” is a fundamental part of sexual health. This holistic definition of sexual health as more than just the absence of disease recognizes that sexual pleasure is an integral component of physical, social, and emotional well-being.

Despite the above, sexual health programs have almost uniformly focused on pregnancy and disease prevention without considering the role of sexual pleasure. Condoms are promoted for their effectiveness against both pregnancy and HIV and other sexually transmitted infections (STIs) and are the only method that provides this dual protection (Holmes et al., 2004; Trussell, 2011; Weller & Davis, 2002). At the same time, condoms are widely perceived as negatively affecting sexual pleasure and arousal. A national survey by the Ministry of Health of Vietnam (2005) found that despite widespread lack of personal experience with the device, about 70% of youth believed that condoms reduce sexual pleasure. This finding is consistent with a large U.S. study, in which 31% of heterosexual male and female condom users reported at least one condom fit or feel problem (Crosby et al., 2013). Given the negative effect on men’s sexual pleasure, some women report not using condoms because of their desire to please their partner or they report reluctance to require condom use because of concerns that their partner will seek condomless sex elsewhere (Higgins & Hirsch, 2008). Some women also resist condom use because condoms dull their own sensations, reduce lubrication, or otherwise reduce their pleasure (Fennell, 2014). Research on contraceptive preference and acceptability suggests that people value methods that do not interfere with sexual pleasure or libido (Higgins et al., 2020; Jackson et al., 2016; Jamin et al., 2017). Perceptions about condoms interfering with sexual pleasure are important because they are directly related to frequency of condom use (Crosby et al., 2013; Higgins et al., 2009; Randolph et al., 2007).

A novel condom, the CSD500 (Futura Medical; Guildford, UK), was designed to increase sexual pleasure by increasing penile blood flow and thereby maximizing erection hardness. CSD500 is a commercial, latex condom with a teat at the end containing a gel with a pharmacological dose of Zanifil™ (active ingredient glyceryl trinitrate 1% w/w). Topical glyceryl trinitrate appears to be effective in treating erectile dysfunction (Ralph et al., 2018); however, CSD500 is novel in that the condom is designed for healthy men to improve their sexual experience. CSD500 complies with the requirements of ISO 4074, the international standard for male latex condoms, and was approved for over-the-counter use by healthy men in the European Union in 2011 and subsequently in Saudi Arabia and the United Arab Emirates.

A condom designed to increase men’s sexual pleasure might facilitate both men and women’s willingness to consistently use condoms. For example, women might face less difficulty asking a male partner to wear a condom that enhances pleasure rather than for pregnancy or disease prevention. Women’s ability to negotiate condom use depends on the nature of the relationship (both type and length) and their power within it (Farrington et al., 2016). Especially in established relationships with expectations of monogamy, introducing condoms may raise sensitive questions of fidelity or trust. In one study of married women in Vietnam, despite believing that men often engage in extramarital relationships, women reported difficulty in negotiating condom use with husbands because condoms were perceived to be an indicator of infidelity (Nguyen et al., 2008). Changing the stated purpose for its use could facilitate this negotiation.

We conducted a randomized controlled trial to evaluate whether CSD500 could increase sexual pleasure, relative to standard condoms, among men and women in Thanh Hoa, Vietnam. Our objectives in the present analysis were to evaluate whether women assigned to use CSD500 had higher scores on the Quality of Sexual Experience (QSE) scale at the 2-, 4-, and 6-month follow-up visits compared to women assigned to use standard condoms. We also assessed whether men in the CSD500 arm had higher QSE scores and Sexual Experience Questionnaire (SEX-Q) scores at the 6-month visit compared to men in the control arm. Finally, we evaluated whether men in the CSD500 had higher measures of acceptability of condom use at the 6-month visit compared to those in the control arm.

Method

Study Design

We conducted a randomized control trial of two groups of heterosexual couples (experimental CSD500 versus control condom) in June 2017 to February 2020 at a provincial health center in Thanh Hoa, in the North Central Coast region of Vietnam. After the couples completed the enrollment visit, the female participants returned for 2-, 4- and 6-month follow-up visits while male participants returned for the 6-month follow-up visit. Condoms are important for pregnancy prevention in settings, such as Southeast Asia, where concerns about the side effects and health risks of hormonal contraception are especially strong (Sedgh & Hussain, 2014). We sited the trial in Vietnam, in part, because the nation has low acceptability of hormonal contraception and one of the highest abortion rates in the world (Committee for Population, Family and Children Vietnam & ORC Macro, 2003; Sedgh et al., 2007). Condom use also is important for prevention of HIV/STIs; HIV incidence in Vietnam was estimated at 0.05 per 1,000 population in 2019 (UNAIDS, 2020). Because CSD500 has not been submitted for regulatory approval for use in Vietnam, we obtained regulatory approval from the Vietnam government to use CSD500 solely for research purposes in compliance with local laws. In the trial, we labeled the CSD500 condoms as “Futura Max,” a product name that pre-testing indicated was acceptable to the target population. The control condom was a lubricated latex condom that was similar in size (52 mm width). The Ohio State University and Hanoi School of Public Health institutional review boards provided ethical review. We registered the protocol before trial initiation at ClinicalTrials.gov (identifier: NCT02934620). To our knowledge, this was the first non-industry study, and the first study publication, on CSD500.

Participants

To be eligible for the study both members of a heterosexual couple had to speak Vietnamese. Female participants had to meet the following criteria: 18–45 years of age; not currently using or intending to start use of any modern contraceptive method other than condoms in the next 6 months; willing to use the assigned study condoms as the sole method of contraception for the next 6 months; not breastfeeding, pregnant or intending to become pregnant within the next 6 months; and in a monogamous relationship for at least the past 6 months with the male partner. Couples were ineligible if either person was known to be HIV-positive or had any of the following contraindications for CSD500 use from the package insert: history of low blood pressure or heart condition; current use of medication for anemia, blood pressure, erectile dysfunction (man only), migraines, headaches, or glaucoma; inflamed or broken skin that the condom could come into contact with (man only); or latex allergy or sensitivity.

Most women resided in a city (56.6%) while the remainder lived in a town (17.4%) or rural area (26.0%; Table 1). Women had a mean age of 32.1 years (SD = 0.24; range 21–46). Most women (74.0%) and men (67.5%) had completed education beyond the upper secondary level. Most women (76.6%) reported at enrollment that they were using condoms for contraception. While we measured women’s age and contraception use, including condoms, during screening, these were not inclusion criteria for the male partner and these data were not collected for men.

Table 1. Demographics of female and male participants (N = 500).

	Female participants				Male participants
	CSD500 arm (n = 248)		Control arm (n = 252)		CSD500 arm (n = 248)		Control arm (n = 252)
	N	%	N	%	N	%	N	%
Age
21–30 years	76	30.7	81	32.1	–	–	–	–
31–35 years	81	32.7	79	31.4	–	–	–	–
≥ 36 years	91	36.7	92	36.5	–	–	–	–
Residence
City	130	52.4	153	60.7	–	–	–	–
Town	47	19.0	40	18.9	–	–	–	–
Rural	71	28.6	59	23.4	–	–	–	–
Highest level of education completed
None or primary	5	2.0	3	1.2	11	4.4	8	3.2
Lower secondary	17	6.9	18	7.1	23	9.3	13	5.2
Upper secondary	49	19.8	38	15.1	55	22.3	52	20.6
Higher	177	71.4	193	76.6	158	64.0	179	71.0
Age at sexual initiation (mean, SD)	23.9	2.7	23.8	2.6	25.4	0.3	25.1	0.2
Lifetime opposite-sex partners
One	233	94.3	232	92.1	163	65.7	164	65.1
More than one	11	4.5	16	6.4	69	27.8	77	30.6
Declined to answer	3	1.2	4	1.6	16	6.5	11	4.4
Live births
0	2	0.8	3	1.2	–	–	–	–
1	40	16.1	32	12.7	–	–	–	–
≥ 2	206	83.1	217	86.1	–	–	–	–
Using condoms at enrollment
Yes	191	77.0	192	76.2	–	–	–	–
No	57	23.0	60	23.8	–	–	–	–

Measures

The primary outcome for the present analysis was the validated QSE scale, which consists of seven questions related to pleasure and satisfaction of event-level sexual experiences (Sanders et al., 2013). The QSE scale was validated among adult men and women in the U.S. by Sanders et al. Each question had a 7-point rating scale, with higher scores indicating a higher-quality experience. We asked male and female participants during enrollment and follow-up visits to answer the QSE questions in reference to their last sex act with their partner. We calculated an overall scale score using the mean of each participant’s item-level responses. Cronbach’s alpha for the QSE ranged from 0.96 to 0.97 at enrollment and 6 months for both women and men.

The SEX-Q, a male-specific sexual satisfaction questionnaire (Mulhall et al., 2008), was a secondary outcome of interest. The SEX-Q asks men to reflect on their sexual experiences over the past four weeks, and report on three domains: erection, individual satisfaction, and couple satisfaction. The scale contains 12 items, each measured on a 5-point rating scale, which were summed and transformed to a 0–100 scale, as described by Mulhall et al. (2008). Higher scores on the SEX-Q indicate higher quality sexual experiences. Cronbach’s alpha for the SEX-Q ranged from 0.86 to 0.89 at enrollment and 6 months. The high Cronbach’s alpha values for both QSE and SEX-Q indicate good internal consistency for the scales.

We also assessed male acceptability of condom use using a series of 11 questions, which we developed for this trial, related to ease of use, fit, sensation, adverse reactions, pleasure, and satisfaction (Table 2). To our knowledge, this was the first time that the QSE and SEX-Q were administered to a population in Vietnam. Based on pretesting of the questionnaires with 10 couples from the target population, no modifications to the scales or 11 items were deemed necessary.

Table 2. Acceptability of condom use at last act among male participants by study arm at 6-month visit.

	CSD500		Control		p-value
	N	(%)	N	(%)
Was the condom easy or hard to put on?
Very easy	33	15.0	15	6.6	<.01
Easy	160	72.8	163	71.8
Neither easy nor difficult	26	11.8	48	21.2
Difficult	1	0.5	0	0.0
Very difficult	0	0.0	1	0.4
Was the condom easy or hard to keep on during sex?
Very easy	22	9.6	11	4.9	.02
Easy	174	79.1	168	74.0
Neither easy nor difficult	23	10.5	45	19.8
Difficult	2	0.9	2	0.9
Very difficult	0	0.0	1	0.4
Was the condom easy or hard to remove?
Very easy	23	10.5	15	6.6	.07
Easy	168	76.4	165	72.7
Neither easy nor difficult	29	13.2	45	19.8
Difficult	0	0.0	2	0.9
Very difficult	0	0.0	0	0.0
How did the condom fit?
Very good	29	13.2	9	4.0	<.01
Good	120	54.6	79	34.8
Average	68	30.9	136	59.9
Below average	3	1.4	2	0.9
Poor	0	0.0	1	0.4
Did the condom feel natural during sex?
Natural	151	68.6	73	32.2	<.01
Average	67	30.5	144	63.4
Not natural	2	0.9	10	4.4
Did the condom make penetration easier or harder than sex without a condom?
Easier	77	35.0	54	23.8	.03
No change	141	64.1	172	75.8
Harder	2	0.9	1	0.4
Did you or your partner experience pain during sex because of the condom?
No	216	98.2	223	98.2	.96
Yes	4	1.8	4	1.8
Did you or your partner experience burning, itching or irritation when using the condom?
No	219	97.8	228	97.9	.95
Yes	5	2.2	5	2.2
Was sex with the condom shorter or last longer than sex without a condom?
Shorter	3	1.4	2	0.9	<.01
No change	123	55.9	214	94.3
Longer	94	42.8	11	4.9
Did you like using the condom?
Like it a lot	40	18.2	8	3.5	<.01
Like it a little	101	45.9	74	32.6
Didn’t matter	63	28.6	111	48.9
Dislike it a little	14	6.4	31	13.7
Dislike it a lot	2	0.9	3	1.3
How did sex with the condom feel to you compared with sex without a condom?
A lot better	34	15.5	12	5.3	<.01
A little better	59	26.8	54	23.8
No different	39	17.7	55	24.2
A little worse	68	30.9	79	34.8
A lot worse	20	9.1	27	11.9

Procedure

Using the electronic data capture program REDCap to conceal the allocation process, we randomized heterosexual couples to one of two arms in a balanced design. Although both the male and female partners had to provide written consent for the couple to be eligible to participate, only the woman received condom counseling. This was designed to be consistent with non-study conditions in which women typically bear the responsibility for condom and contraception uptake in clinic settings. Female study staff, consisting of health-care providers, distributed CSD500 condoms to women in the intervention arm together with counseling that briefly explained the condom’s ability to protect against pregnancy and HIV/STI and then emphasized the potential for increased sexual pleasure from the condom’s erectogenic gel. This counseling included the following message: “Futura Max condoms are designed to make sex more fun for the couple. The condoms contain a special gel that makes the man’s erection get harder and last longer. This can make sex more pleasurable for the couple.” Trained staff counseled women in the intervention arm to squeeze the teat of the donned condom to massage the gel onto the head of the penis for 15 seconds to facilitate its absorption. Women in the control arm received a standard condom available locally with the standard counseling message to use the condoms for pregnancy and disease prevention (i.e., no message about sexual pleasure). The primary aim of the trial, which will be reported elsewhere, was to determine if CSD500 resulted in less condomless vaginal sex, as measured by detectible levels of prostate specific antigen in vaginal fluid at follow-up visits scheduled at 2, 4 and 6 months after enrollment.

During study planning, questionnaires were translated into Vietnamese and then back-translated into English to confirm the accuracy of translation. Questionnaires were pretested with 10 couples from the target population and the phrasing of questions and responses were adjusted as needed. During the trial, female interviewers administered questionnaires via REDCap to female participants at enrollment and the 2-, 4-, and 6-month follow-up visits and to male participants at enrollment and the 6-month follow-up visit. Participants completed the questionnaires without their partner present. At the 2- and 4-month visits, study staff repeated the condom counseling and dispensed the assigned condom type (9 times the expected weekly coital frequency as reported by the female participant or 20 condoms, whichever was greater) to the female participant. All study procedures were performed in a private setting at the study site.

Data Analysis

We calculated means and standard deviations (SDs) of item-level QSE and SEX-Q responses at enrollment for men and women and at follow-up (2-, 4-, and 6-month visits for women and 6-month visit for men). We used linear regression to compare QSE scores between women in the intervention and control arms during the follow-up period, controlling for baseline QSE scores, using generalized estimating equations with an independent working correlation to account for multiple visits from individual women. Comparison of QSE scores for men in the intervention and control groups at the 6-month visit, controlling for baseline QSE scores, were analyzed using linear regression. We repeated these analyses for men’s responses to the SEX-Q items, domain scores (i.e., erection, individual satisfaction, and couple satisfaction) and global score. As sensitivity analyses, we repeated models restricting the analysis sample to those who reported using a condom at the last sex act. This sensitivity analysis included 1,073 follow-up visits from 441 women and 361 men for the QSE analysis and 360 men for the SEX-Q analysis at the six-month visit. Finally, we tabulated men’s survey responses at the six-month visit to a series of condom acceptability questions and used chi-squared tests to assess differences between the intervention and control arms.

Results

A total of 500 couples enrolled in the trial: 248 in the CSD500 arm and 252 in the control arm. Similar numbers of women in the intervention and control arm completed the 2-month visit (233 and 228, respectively), 4-month visit (228 and 220, respectively) and 6-month visit (234 and 239, respectively). Similar numbers of men in the intervention and control arms completed the 6-month visit (230 and 238, respectively). We had little missing data among those completing the study visit. For example, we were missing QSE scores for 1 woman who attended the 2-month visit, and for 2 women at the 4- and 6-month visits. We were missing QSE scores for 2 men and SEX-Q scores for 3 men who attended the 6-month visit.

Women and men in the CSD500 arm reported higher QSE scores during follow-up compared to their counterparts in the control arm (Table 3). QSE scale scores were higher during the follow-up period among women in the CSD500 arm relative to those in the control arm (B = 0.12; 95% CI, 0.03–0.21). Similarly, the average QSE scale score for men at the 6-month visit was higher for the CSD500 arm compared to the control arm (B = 0.21; 95% CI, 0.08–0.35). Likewise, the SEX-Q scale score was higher at the 6-month visit among men in the CSD500 arm compared to men in control arm (B = 3.22; 95% CI, 1.53–4.91; Table 4). As a sensitivity analysis, we repeated the analyses after restricting the population to those who reported using a condom at the last sex act, and the same differences by study arm remained (data not shown).

Table 3. Quality of sexual experience (QSE) among female and male participants by study visit (N = 500).

	Enrollment visit			2-month visit			4-month visit			6-month visit
	N^b	Mean	(SD)	N^b	Mean	(SD)	N^b	Mean	(SD)	N^b	Mean	(SD)	B^c	(95% CI)
Women’s QSE scale score^a
CSD500 arm	245	5.20	0.84	233	5.27	0.84	226	5.20	0.71	233	5.23	0.72	0.12	(0.03, 0.21)
Control arm	247	5.25	0.89	227	5.13	0.72	220	5.07	0.70	238	5.14	0.61	Ref
Men’s QSE scale score^a					–	–		–	–
CSD500 arm	248	5.44	0.80		–	–		–	–	229	5.48	0.79	0.21	(0.08, 0.35)
Control arm	252	5.50	0.78		–	–		–	–	237	5.27	0.66	Ref

^aScale scores were calculated as the mean of the individual’s response to 7 items, each of which had a 7-point rating scale, with higher scores indicating higher quality sexual experiences.

^bParticipants were only included in the analysis if they had non-missing values for all scale items.

^cB is the estimated difference in scale scores during follow up for the CSD500 arm compared to the control arm, adjusting for baseline scores. Analysis for women used generalized estimating equations to account for multiple visits of female participants.

Table 4. Sexual experience questionnaire (SEX-Q) among male participants by study visit.

	Enrollment visit (n = 500)		6-month visit (n = 466)
SEX-Q items and domain and global scores^a	Mean	SD	Mean	SD	B^b	(95% CI)
Erection domain score
CSD500 arm	72.30	10.73	77.20	9.60	3.45	(1.77, 5.17)
Control arm	73.23	10.14	73.86	9.24	Ref.
How often were you able to maintain an erection for as long as you wanted to?
CSD500 arm	4.00	0.71	4.31	0.57	0.19	(0.09, 0.28)
Control Arm	4.09	0.64	4.14	0.51	Ref.
During sexual intercourse, how often were you able to penetrate your partner?
CSD500 arm	4.53	0.60	4.68	0.48	0.09	(0.00, 0.18)
Control Arm	4.56	0.54	4.60	0.53	Ref.
How much have you worried about whether you could get an erection?^c
CSD500 arm	4.43	0.76	4.70	0.55	0.15	(0.04, 0.26)
Control Arm	4.48	0.74	2.55	0.66	Ref.
How confident were you that you could get an erection when you wanted to?
CSD500 arm	3.22	0.75	3.38	0.62	0.11	(0.00, 0.23)
Control Arm	3.20	0.72	3.27	0.64	Ref.
How satisfied were you with the hardness of your erection?
CSD500 arm	3.60	0.62	3.72	0.57	0.12	(0.02, 0.23)
Control Arm	3.62	0.63	3.59	0.57	Ref.
How satisfied were you with the duration of your erection?
CSD500 arm	3.58	0.64	3.73	0.57	0.17	(0.07, 0.27)
Control Arm	3.62	0.65	3.57	0.57	Ref.
Individual satisfaction domain score
CSD500 arm	61.86	13.40	64.19	11.89	2.27	(0.13, 4.42)
Control arm	63.62	13.08	62.15	11.79	Ref.
How satisfied were you with your level of sexual desire?
CSD500 arm	3.56	0.63	3.67	0.56	0.08	(−0.02, 0.18)
Control Arm	3.62	0.64	3.60	0.55	Ref.
How satisfied were you with your overall sexual activity?
CSD500 arm	3.56	0.64	3.69	0.57	0.15	(0.04, 0.25)
Control Arm	3.63	0.59	3.55	0.58	Ref.
How much pleasure did you get from sexual activity?
CSD500 arm	3.30	0.63	3.34	0.55	0.03	(−0.65, 0.13)
Control Arm	3.39	0.63	3.31	0.55	Ref.
Couple satisfaction domain score
CSD500 arm	61.49	13.23	64.74	11.95	3.50	(1.41, 5.59)
Control arm	63.56	13.95	61.53	11.25	Ref.
How confident were you that you could satisfy your partner during sexual activity?
CSD500 arm	3.25	0.64	3.38	0.55	0.13	(0.04, 0.23)
Control Arm	3.29	0.66	3.25	0.52	Ref.
How often did you achieve mutual satisfaction with your partner?
CSD500 arm	3.67	0.60	3.76	0.57	0.13	(0.03, 0.23)
Control Arm	3.81	0.66	3.65	0.57	Ref.
How satisfied were you with your ability to control the timing of your ejaculation?
CSD500 arm	3.46	0.68	3.63	0.58	0.15	(0.05, 0.25)
Control Arm	3.53	0.68	3.49	0.56	Ref.
SEX-Q global score
CSD500 arm	66.99	10.17	70.83	9.67	3.22	(1.53, 4.91)
Control arm	68.41	10.42	67.82	9.08	Ref

^aScale scores consists of sum of items, each of which could range from 0 to 5 points, which was then converted to a 100-point scale. Higher scores indicate higher quality sexual experiences.

^bB is the estimated difference in scale scores during follow up for the CSD500 arm compared to the control arm, adjusting for baseline scores.

^cItem was scored backward per Mulhall et al. (2008), such that higher scores indicate higher quality sexual experience.

Eight of the 11 items about the last condom use showed statistically significantly greater acceptability among men in the CSD500 arm compared to the control arm at the six-month visit. Higher proportions of men in the CSD500 arm relative to those in the control arm reported that at last condom use the device was “very easy” to put on (15.5% versus 6.6%, respectively; p < .01) and “very easy” to keep on (9.6% versus 4.9%; p = .02; Table 2). Higher proportions of men in the CSD500 arm also reported that the condom fit was “very good” (13.2%) and the condom felt “natural” during sex (i.e., similar to condomless sex) (68.6%) compared to men in the intervention arm who reported a “very good” fit (4.0%; p < .01) and “natural” feel (32.3%; p < .01). Compared to sex without a condom, 42.8% of men in the CSD500 arm versus 4.9% of those in the control arm reported that sex with the study condom lasted longer (p < .01). Higher proportions of men in the CSD500 compared to the control arm “liked it a lot” (18.2% versus 3.5%; p < .01) and reported that sex with the condom felt “a lot better” compared with sex without a condom (15.5% versus 5.3%; p < .01).

Discussion

In this randomized controlled trial of a new condom containing erectogenic gel among adult heterosexual couples in Vietnam, both men and women reported greater sexual pleasure from the use of CSD500 compared to a standard condom. Increased sexual pleasure with CSD500 was consistent across the range of measures, which included the QSE completed by women at 2, 4 and 6-month visits and the QSE, SEX-Q and a series of individual items completed by men at the 6-month visit. The differences between study arms in the QSE and SEX-Q scale scores were relatively modest. Both the QSE and SEX-Q had been validated among adults in the U.S. (Mulhall et al., 2008; Sanders et al., 2013). However, although we pretested the questions among the target population, we did not validate the scales in the target population, and it could be that other questions would have been more appropriate to capture greater variation in sexual pleasure in the target population.

We found larger differences between study arms when examining the series of 11 condom acceptability questions. One possible explanation for the larger differences found with this series of questions might be because they asked about condom use at the last act specifically. In contrast, the QSE and SEX-Q scale items asked about the last act or the sex acts during the last 4 weeks, respectively, regardless of whether condoms were used. Collectively, however, the QSE, SEX-Q and series of 11 condom items consistently indicate greater sexual pleasure with CSD500 among both men and women relative to a standard condom. Several of the differences were especially large – 30% points or greater – suggesting good prospects for CSD500 use.

Increasingly, the importance of sexual pleasure has been recognized for informing interventions on safer sex (Cecil et al., 2010; Crosby et al., 2010; García & Goldman, 2003, 2004; Philpott et al., 2006). Condoms have been modified in terms of their size, taste, appearance, texture, smell, and thickness to improve the user experience (Cecil et al., 2010; Crosby et al., 2010). Eroticizing the protection afforded by condoms appears to be a successful strategy employed by consistent condom users in Mexico and the Dominican Republic (García & Goldman, 2003, 2004). Other interventions have included selling condoms packaged with water-based lubricant sachets as pleasure enhancements in Cambodia and socially-marketing textured male condoms in Uganda (Philpott et al., 2006). The findings here support the conclusions of previous studies that the likelihood of condom use is significantly influenced by perceived effects on sexual pleasure. CSD500 is unique, however, in using an erectogenic compound to increase sexual pleasure, and the present study was the first to document its effect on men and women’s reports of pleasure.

Strengths and Limitations

A primary study limitation is that the study arms were unblinded and thus those assigned to use the intervention condom could have been influenced by a placebo effect. That is, women in the CSD500 arm were counseled on the potential for increased sexual pleasure from the condom’s erectogenic gel; this counseling could have primed women, and indirectly their male partner, to expect and notice more pleasure from using the condom. We opted for an unblinded design because we aimed to make study conditions reflect real life as much as possible. To this end, study staff counseled the woman – rather than her male partner or the couple – on condom use to more closely mimic non-study conditions, in which women typically bear the responsibility for condom and contraception uptake in clinic settings. It is possible that directly counseling men to expect greater pleasure with CSD500 use might lead to stronger effects. Findings are also limited in that they might not be generalizable beyond the study population of adult, reproductive-age couples in an established heterosexual relationship in Thanh Hoa, Vietnam who at enrollment were not using, or intended to start using, contraception other than condoms and who did not desire pregnancy. For example, given that most of the study participants were using condoms at enrollment, they might have been more likely to perceive condom use as “natural” and less likely to perceive condomless sex as feeling better compared to other populations.

The randomized design was a primary strength in that the study arms can be assumed to be comparable at enrollment due to randomization; thus, differences in sexual pleasure between arms can be attributed to the study condoms. Another strength was the high follow-up rate (87%–95% of visits among women and 93%–94% among men), which reduces the potential for attrition bias. Possible reasons for the high follow-up rate include the relatively stable study population, clinically experienced study staff, the highly regarded health center where the study was conducted, novelty of the research topic, and use of study procedures to remind participants of upcoming visits. Finally, higher sexual pleasure attributable to CSD500 persisted throughout the study period. The 6-month study period was selected to ensure that the study findings captured more than simply initial differences that might be due only to the novelty of the intervention condom.

Conclusions

CSD500 appears to hold considerable potential for its role as a condom that could improve men and women’s sexual pleasure. Although the extent of gender inequality can vary in different settings, women’s difficulty in negotiating condom use – especially in the context of a long-term partnership – is a universal theme (Higgins & Smith, 2016; Peasant et al., 2015), and a condom that increases sexual pleasure could hold public health importance globally for the prevention of both HIV/STIs and unintended pregnancy. Future research is warranted to determine whether CSD500 leads to increased sexual pleasure among populations in other geographic or cultural settings as well as with individuals who are not in established heterosexual relationships.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Research reported in this publication was supported by the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Number R01HD084637 and the National Center for Advancing Translational Sciences (UL1TR001070). Futura Medical Developments provided CSD500 for the study at no cost without having any other role or influence. The authors have no conflicts to declare. The content is solely the responsibility of the authors and does not necessarily represent the official views of the funders.