Crystal Meth, GHB/GBL and Mephedrone form what some health workers call an 'un-holy trinity' of drugs that together can heighten arousal and strip away inhibitions.
They've become increasingly popular on London's gay scene, and the effects can see some users taking part in weekend-long sex parties, involving multiple partners.
For Radio 4's The Report, Mobeen Azhar speaks to men entrenched in this lifestyle and explores the impact the so-called 'chemsex' scene is having on public health services.
It's a scene where unsafe sex is common and has been cited as a contributing factor in the rising number of HIV infections in London, posing new challenges to those trying to promote the safe sex message.
Such parties are fuelled by technology and smartphone dating apps, which have triggered a social shift where men have moved out of bars and clubs and into private homes - out of reach to sexual health and drug advice services.
A potential solution to help protect those involved in the scene is Pre Exposure Prophylaxis (PrEP) - the practice of issuing men with HIV medication before they become HIV positive, which studies have shown as an effective means to reduce HIV infection.
PrEp has been championed by the World Health Organisation, saying it could prevent 1 million new HIV infections around the world. Its advocates in Britain suggest it should be made available on-demand as soon as possible - but how affordable is it? And will fears that it will only encourage more unsafe sex prove true?
Presenter: Mobeen Azhar
Producer: Richard Fenton-Smith.
Terrence Higgins Trust
Terrence Higgins Trust is an HIV and sexual health charity which offers a wide range of support services, including emotional support and information by phone, help with accessing HIV testing, treatment advice and counselling. Whatever your sexuality, HIV status, gender, cultural background or ethnic origin, THT has services set up with your needs in mind. If you’re affected by HIV, then they’ll try to help.
Call 0808 802 1221 or email email@example.com for confidential advice and support.
Positively UK is a national charity supporting people living with HIV and their partners. If you want to talk to another person living with HIV you can call the peer support helpline. They also provide a service for 16-24 year olds living with HIV, led by young people also living with HIV. If you are dealing with a new diagnosis, or coming to terms living with HIV and would like the right support and information, you can get in touch.
Support Line: 0207 713 0444 or visit http://positivelyuk.org/young-people/
FRANK provides a confidential, free service to anyone wanting information, advice or support about any aspect of drugs.
Helpline: 0300 123 6600 Minicom: 0300 123 1099 Text a question: 82111
Online chat facility (available between 2-6pm throughout the week)
The Club Drug Clinic
London Lesbian & Gay Switchboard
London Lesbian & Gay Switchboard (LLGS) provides an information, support and referral service for lesbians, gay men, bisexual, trans people and anyone who needs to consider issues around their sexuality. The services include a helpline, online chat through instant messaging, email support, information on sexual health and the Turing Network database, a public access search facility that enables anyone to look for support or services catering for the LGBT community.
Helpline: 0300 330 0630
Sex Worth Talking About
Brook provides sexual health services and advice for all young people under 25 at their services around the UK. Ask Brook offers interactive text and webchat services.
Text: 07717 989 023 (standard SMS rates apply)
The Site is a digital lifeline for 16 to 25 year-olds. They provide non-judgmental support and information on everything from sex and exam stress to debt and drugs. TheSite’s straight-talking emotional support is available 24 hours a day. On TheSite you can chat about any issue on their moderated discussion boards and in their live chat room, browse over 2000 articles and videos full of facts you can trust, read about the experiences of other young people in their True Life section, or ask one of their trained advisors any question, whether that's about friends, dating, love or family life.