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Microbicides and PrEP

a man's hand over a woman's hand

Microbicides and Pre-exposure prophylaxis (PrEP) are two methods of preventing the spread of HIV that could be used before you have sex. Microbicides are still in development but PrEP is already here although not yet available through the NHS in the UK.

PrEP cannot protect against other sexually transmitted infections (STIs) or an unwanted pregnancy, so it’s best to use a condom as well.

What are microbicides?

A microbicide is a substance that can stop microbes in the form of viruses or bacteria from entering the cells by either destroying them or by acting as a barrier.

Microbicides could therefore be developed to protect against:

  • HIV
  • STIs
  • pregnancy (by using spermicides).

Microbicides are usually applied inside a woman’s vagina (possibly a gel, cream or ring that releases a drug).

Challenges in microbicide research

Work is underway to produce microbicides that kill HIV or otherwise stop the virus infecting a partner during sex. Some aim to deliver anti-HIV drugs into the vagina where they may be able to stop the virus infecting the woman.

Research is also underway to develop microbicides for use in the rectum to stop infection in women and men during anal sex. These would most likely have to be formulated in a different way as there are differences in the skin of the anus and that of the vagina. Also the vagina is a contained space and the anus is open ended.

What we know so far

Results from trials of vaginal microbicides have given mixed results, so if an effective product can be developed it ‘s likely to take some time before it’s available. Even then, any microbicide would be unlikely to give 100% protection, so would need to be used together with another HIV prevention method such as condoms.

Results of two recent vaginal ring trials found both products to be moderately effective at preventing HIV infection – with the product offering protection in a third of cases. In fact the rings offered no protection at all to women aged 18-21 years old - which were the groups with the highest rates of infection.

Research is continuing into one of the rings tested with the hope scientists can learn why it was less effective in younger women and how this can be improved.

What is PrEP?

PrEP is a course of HIV drugs taken by someone who is HIV negative, at high risk of HIV and who is finding it hard to use condoms, in order to stop them getting HIV. This means taking HIV medication during the period they’re at risk.

Results in trials have been very successful, with PrEP significantly lowering the risk of becoming HIV positive and without major side effects.

The medication used for PrEP is a tablet called Truvada, which contains tenofovir and emtricitabine (which are drugs commonly used to treat HIV).

The drugs used in PrEP are the same drugs that are prescribed to thousands of people living with HIV every year. They are very safe and have no serious side effects. A few people experience nausea, headaches or tiredness and, very rarely, the medication can affect kidney function. As a precaution people taking PrEP have regular kidney tests.

Where to get PrEP

PrEP is not currently available on the NHS, but it’s available by private prescription from some clinics.

In December 2016, NHS England announced they would fund a trial of PrEP. In April 2017, it was announced that people at risk of HIV in Scotland would be able to access PrEP through the NHS, and the Government in Wales decided to implement a PrEP trial. For the latest information on these developments, see our full guide to PrEP.

Some people are also ordering a cheaper, generic version of Truvada online - called Tenvir-EM.

If you’re thinking about getting PrEP from outside the NHS, it’s really important that you talk to your sexual health clinic. They should be able to help you with getting safety checks on your kidneys and might be able to suggest ways you can get tests done to make sure the drug is legitimate too.

You can find out more with our full guide to PrEP ››



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The Information Standard: Certified member

This article was last reviewed on 22/6/2016 by Anna Peters

Date due for the next review: 22/6/2019

Content Author: Kerri Virani

Current Owner: Health Promotion

More information:

Pragmatic Open-Label Randomised Trial of Pre-Exposure Prophylaxis: the PROUD study, PROUD, MRC Clinical Trials Unit & Public Health England, February 2015

PROUD study interim analysis finds pre-exposure prophylaxis (PrEP) is highly protective against HIV for gay men and other men who have sex with men in the UK, PROUD, MRC Clinical Trials Unit & Public Health England, October 2014

PrEP briefing paper, Roger Pebody, NAM aidsmap, July 2015

Second European PrEP study closes placebo arm early due to high effectiveness, Gus Cairns, NAM aidsmap, October 2014

Risk of Drug Resistance Among Persons Acquiring HIV Within a Randomized Clinical Trial of Single- or Dual-Agent Pre-exposure Prophylaxis, The Journal of Infectious Diseases, March 2014

Next steps for PrEP: Getting a proven prevention option to the people who need it, Deirdre Grant and Kay Marshall, Treatment Issues, June 2013

An Angle on Long-Term Side Effect Risk With TDF/FTC PrEP in Weighing Risks of TDF/FTC PrEP Side Effects in People Without HIV, Mark Mascolini from The Center for AIDS, The Body Pro, Winter 2012

Emtricitabine-tenofovir concentrations and pre-exposure prophylaxis efficacy in men who have sex with men, Anderson PL1, Glidden DV, Liu A, Buchbinder S, Lama JR, Guanira JV, McMahan V, Bushman LR, Casapía M, Montoya-Herrera O, Veloso VG, Mayer KH, Chariyalertsak S, Schechter M, Bekker LG, Kallás EG, Grant RM; iPrEx Study Team; Science Translational Medicine, September 2012

Antiretroviral Prophylaxis for HIV Prevention in Heterosexual Men and Women, The New England Journal of Medicine, August 2012

PrEP Works... If You Take It, PrEP efficacy table from www.prepwatch.org

PrEP, NAM aidsmap, Roger Pebody, July 2015

What is Truvada? Truvada, 2014

Post-exposure prophylaxis (PEP), Michael Carter, Greta Hughson, NAM aidsmap, September 2012

PEP, PEPSE, PrEP and TASP!, iBase, February 2013

HIV in the UK: Situation Report 2015, Skingsley A, Yin Z, Kirwan P, Croxford S, Chau C, Conti S, Presanis A, Nardone A, Were J, Ogaz D, Furegato M, Hibbert M, Aghaizu A, Murphy G, Tosswill J, Hughes G, Anderson J, Gill ON, Delpech VC and contributors. HIV in the UK –Situation Report2015: data to end 2014. November 2015. Public Health England, London

Vaginal rings containing antiretroviral moderately effective – but not in the youngest women, Gus Cairns, NAM aidsmap, February 2016

What are microbicides, aids.gov

Microbicides, NAM aidsmap

Pragmatic Open-Label Randomised Trial of Pre-Exposure Prophylaxis: the PROUD study, PROUD, MRC Clinical Trials Unit & Public Health England, February 2015

PROUD study interim analysis finds pre-exposure prophylaxis (PrEP) is highly protective against HIV for gay men and other men who have sex with men in the UK, PROUD, MRC Clinical Trials Unit & Public Health England, October 2014

Microbicides, NAM (2012)

Pre-exposure prophylaxis (PrEP), NAM (2011)

Post-exposure prophylaxis, NAM (2011)

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