Magnetic resonance imaging of SILCS diaphragm: anatomical considerations and corroboration with clinical fit

A modified SILCS contraceptive diaphragm for long-term controlled release of the HIV microbicide dapivirine

BACKGROUND

There is considerable interest in developing new multipurpose prevention technologies to address women's reproductive health needs. This study describes an innovative barrier contraceptive device--based on the SILCS diaphragm--that also provides long-term controlled release of the lead candidate anti-HIV microbicide dapivirine.

STUDY DESIGN

Diaphragm devices comprising various dapivirine-loaded polymer spring cores overmolded with a nonmedicated silicone elastomer sheath were fabricated by injection molding processes. In vitro release testing, thermal analysis and mechanical characterization were performed on the devices.

RESULTS

A diaphragm device containing a polyoxymethylene spring core loaded with 10% w/w dapivirine provided continuous and controlled release of dapivirine over a 6-month period, with a mean in vitro daily release rate of 174 mcg/day. The mechanical properties of the new diaphragm were closely matched to the SILCS diaphragm.

CONCLUSIONS

The study demonstrates proof of concept for a dapivirine-releasing diaphragm with daily release quantities potentially capable of preventing HIV transmission. In discontinuous clinical use, release of dapivirine may be readily extended over 1 or more years.

Vaginal rings for delivery of HIV microbicides

Following the successful development of long-acting steroid-releasing vaginal ring devices for the treatment of menopausal symptoms and contraception, there is now considerable interest in applying similar devices to the controlled release of microbicides against HIV. In this review article, the vaginal ring concept is first considered within the wider context of the early advances in controlled-release technology, before describing the various types of ring device available today. The remainder of the article highlights the key developments in HIV microbicide-releasing vaginal rings, with a particular focus on the dapivirine ring that is presently in late-stage clinical testing.

Controlled-release vaginal ring drug-delivery systems: a key strategy for the development of effective HIV microbicides

BACKGROUND

Over half of all HIV-infected adults are women and heterosexual intercourse is a significant mode of viral transmission. This review examines the potential for using polymeric vaginal ring systems to provide controlled delivery of HIV microbicides in order to prevent heterosexual transmission of the virus.

DISCUSSION

Continuous delivery of microbicides has the potential to be more effective than one-off dosing. Thus, controlled-release vaginal delivery devices are now a key area of HIV prevention research. Initial clinical trials on vaginal rings loaded with dapivirine (a candidate microbicide) have indicated that these products are safe and well tolerated by women. These devices are female-initiated, robust and capable of long-term delivery of the active agent.

CONCLUSIONS

Vaginal rings may offer an effective system for the controlled delivery of microbicides to prevent heterosexual transmission of HIV. Candidate vaginal ring microbicide products are now in clinical trials.

Couples' acceptability of the SILCS diaphragm for microbicide delivery

BACKGROUND

Disposable plastic applicators used in microbicide gel studies are expensive and have a negative environmental impact. The SILCS diaphragm is a barrier contraceptive that could offer a reusable delivery system.

STUDY DESIGN

Thirty-six couples in this randomized, cross-over study evaluated single- and double-sided gel delivery from a SILCS diaphragm compared with gel from an applicator. Couples used each gel scenario during two acts of intercourse and completed acceptability questionnaires after each.

RESULTS

All three scenarios received favorable ratings for ease of application, acceptability and perceived effectiveness. Both female and male participants tended to rate the gel applicator significantly more favorably than either SILCS gel delivery scenarios for all attributes except messiness/leakage and effectiveness. Additionally, about 60% of female participants and about half of male participants preferred the gel applicator to either of the gel delivery systems using SILCS. The preference for the SILCS scenario for pregnancy protection was statistically significant for both sexes. Male participants were also significantly more likely to prefer the SILCS single-sided delivery system to the gel applicator for protection from sexually transmitted infection.

CONCLUSIONS

In this study population, participants found the gel applicator to be more acceptable than either single- or double-sided gel delivery from a SILCS diaphragm. Further research of the SILCS as a microbicide delivery system should be implemented to assess its acceptability among study populations that reflect diverse potential user groups such as women and men from both low and high HIV prevalence settings including HIV-positive populations and with and without experience using female barrier methods.

Development of a microbicide-releasing diaphragm as an HIV prevention strategy

Contraceptive diaphragms offer a discreet method of pregnancy protection that women can use when needed with no side effects. Incorporating antiretroviral HIV microbicides into such devices may also provide protection against HIV infection. The paper gives a brief outline of the work being conducted by PATH, CONRAD and QUB on the development of a microbicide-releasing SILCS diaphragm. The design, engineering and manufacturing challenges that have been encountered will be discussed, as well as the potential impact such a device could have in the developing world.

SILCS diaphragm: postcoital testing of a new single-size contraceptive device

BACKGROUND

This study was conducted to compare the effectiveness of a new, single-size silicone contraceptive diaphragm used with either spermicide [2% nonoxynol-9 (N-9)] or lubricant in preventing sperm from penetrating midcycle cervical mucus.

STUDY DESIGN

A crossover postcoital test (PCT) in healthy, sexually active women not at risk for pregnancy due to tubal occlusion was conducted. Couples had a baseline PCT without a device to verify normal fertility parameters. Qualified couples underwent up to two test cycles using the SILCS diaphragm with a metal spring. A subgroup of couples underwent a third test cycle with the SILCS polymer spring diaphragm used with N-9 gel.

RESULTS

Fifteen couples completed a baseline cycle and were randomized to order of study gel. Of these, 14 couples completed a baseline cycle and at least one test cycle, 12 couples completed a baseline cycle and two test cycles and 8 couples completed a third test cycle with the polymer spring prototype. Sperm was detected in the vaginal pool in all completed test cycles. The SILCS metal spring diaphragms used with N-9 gel reduced the average number of progressively motile sperm per high power field in the cervical mucus from a baseline of 12.5 to 0, while use of this device with lubricant reduced the number to 0.5. The SILCS polymer spring diaphragm used with N-9 performed the same as the metal spring used with N-9.

CONCLUSION

The SILCS diaphragm used with N-9 gel performed well. It is likely that the SILCS diaphragm will give acceptable results in a contraceptive effectiveness study but that adjunctive use of a chemical barrier such as N-9 gel will be necessary for it to be most effective.