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Microbicides

What they are

Microbicides are compounds that can be applied inside the vagina or rectum to protect against sexually transmitted infections (STIs) including HIV. They can be formulated as gels, creams, films, or suppositories. Microbicides may or may not have spermicidal activity (contraceptive effect). At present, an effective microbicide is not available.

Why they are Important

It is important to support the development of microbicides because:

  • Despite the knowledge of successful HIV prevention strategies – condom use, reduction in the number of sexual partners, diagnosis and treatment of sexually transmitted infections – HIV continues to spread at an alarming rate especially among women in developing countries;
  • Without a preventive HIV vaccine, microbicides offer an alternative to condoms as the most feasible method for primary prevention of HIV.
  • Currently available HIV prevention techniques are often not feasible for many women who live in resource poor settings. The availability of microbicides would greatly empower women to protect themselves and their partners. Unlike male or female condoms, microbicides are a potential preventive option that women can easily control and do not require the cooperation, consent or even knowledge of the partner.

How they Work

There are different ways in which microbicides act to prevent infection with genital pathogens. Some microbicides (e.g Carraguard®, Cyanoviran®, cellulose sulphate, PRO 2000®) provide a physical barrier that keeps HIV and other pathogens from reaching the target cells. Another class of microbicides (e.g. Acidform®, BufferGel® and Lactobacillus crispatus) act by enhancing the natural vaginal defence mechanisms by maintaining an acidic pH, which protects the vagina. C31G and octoxynol-9 kill or disable pathogens by stripping them of their outer covering. Another class of products e.g tenofovir (PMPA) acts by preventing replication of the virus after it has entered the cell. There are 23 microbicide products in various stages of clinical development. Carraguard®, a product of the Population Council, is in Phase III effectiveness trial in South Africa and Botswana. Phase II/III studies of BufferGel® and PRO 2000® are on-going in India, Malawi, South Africa, United Republic of Tanzania and Zimbabwe. Expanded Phase II studies are in progress for Carraguard, dextrin sulphate, Lactobacillus crispatus and PRO 2000®. Products that are in Phase I include Acidform®, C31G, cellulose sulphate, and tenofovir.

Nonoxynol-9 is a spermicide which has been in widespread use as a contraceptive for many years. It is available over-the-counter in different formulations (gels, suppositories and film) and can be used alone or as additional protection on top of condoms, diaphragms or other physical barrier methods.

Considerable research has been done on the safety and effectiveness of Nonoxynol-9 for HIV prevention. WHO, in collaboration with the CONRAD Program, convened a technical consultation in October 2001 to review the data on the use of Nonoxynol-9 as a spermicide.

Key conclusions from the technical consultation include:

  • Although nonoxynol-9 has been shown to increase the risk of HIV infection when used frequently by women at high risk of infection, it remains a contraceptive option for women at low risk.
  • Nonoxynol-9 offers no protection against sexually transmitted infections such as gonorrhoea or chlamydia.
  • There is no evidence that condoms lubricated with nonoxynol-9 are any more effective in preventing pregnancy or infection than condoms lubricated with silicone, and such condoms should no longer be promoted. However, it is better to use an nonoxynol-9 lubricated condom than no condom at all.
  • Nonoxynol-9 should not be used rectally.
  • Evaluation of other potential microbicides should continue.

Human Resources, Infrastructure and Supplies Needed

Distribution of microbicides will be influenced to a large extent by whether they are available for sale by prescription or over-the-counter (OTC). If an effective microbicide becomes available for use on the market as an OTC it can use the same distribution system as condoms. Their use can be advocated for in HIV/AIDS, STI, maternity and family planning clinics, and in youth or adolescent health care. Health care personnel working in this variety of settings can be trained in the use – and importance – of microbicides.

Cost Information

A recent cost-benefit analysis conducted at the London School of Hygiene and Tropical Medicine indicates that the introduction in 73 lower-income countries of a microbicide which reduced the risk of infection by 40%, at 30% coverage, would avert approximately 6 million HIV infections over 3 years in men, women and children (Charlotte Watts, personal communication). In addition, this would reduce the health care costs (excluding the cost of antiretroviral therapy) by a staggering 3.2 billion US dollars. This implies that a microbicide with relatively low-effectiveness could have a substantial impact against the global HIV epidemic if it were used by a significant number of women.

Key References

  • UNAIDS, International Working Group on Vaginal Microbicides, Recommendations for the development of microbicides. AIDS 1996, 10:1-6.
  • Ramjee G, Gouws E, Andrews A, Myer L, Weber AE. The acceptability of a vaginal microbicides among South African men. International Family planning Perspectives 2001, 27:164-170.
  • Lerner S. Microbicides: a woman-controlled HIV prevention method in the making. SIECUS Rep 1994: 22:10-3.
  • Berer, M. Microbicides 2000: report of an International Conference, 13-16 March, Washington, DC. Reprod Health Matters 2000; 8:126-31.
  • UNAIDS. AIDS epidemic update, December 2001: Joint United Nations Programme on HIV/AIDS and the World Health Organization, 2001.
  • Van Damme L, Ramjee G, Alary M, et al. Effectiveness of COL-1492, a nonoxynol-9 vaginal gel, on HIV-transmission among female sex workers. Lancet 2002; 360:971-977.
  • www.who.int/reproductive-health/rtis/ N9_meeting_report.pdf
  • Wilkinson D, Tholandi M, Ramjee G, Rutherford GW. Nonoxynol-9 spermicide for prevention of vaginally acquired HIV and other sexually transmitted infections: systematic review and meta-analysis of randomised controlled trials including more than 5000 women. Lancet Infectious Diseases 2002; 2:613-617.

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