The act of having sex while under the influence of drugs (otherwise known as chemsex) needs to become a public health priority, experts have warned.
'Chemsex' typically refers to intentional sex under the influence of psychoactive drugs, mostly among men who have sex with men.
The growing popularity of chemsex may be putting users at risk of HIV and other sexually transmitted infections as well as serious mental health problems through drug dependence.
The report has been published in The British Medical Journal by a group of specialists working in sexual health and substance abuse in London.
Chemsex refers particularly to the use of mephedrone, gamma-hydroxybutyrate (GHB), gamma-butyrolactone (GBL), and crystallised methamphetamine.
These drugs are often used in combination to facilitate sexual sessions lasting several hours or days, with multiple sexual partners.
At Antidote - a specialist drugs service for the lesbian, gay, bisexual, transgender community in London - two thirds (64%) of attendees seeking support for drug use reported using chemsex drugs in 2013-14.
Of crystal meth and GHB/GBL users, most reported using them to facilitate sex, with around three quarters reporting injecting drug use.
Funding for drugs services in the UK is currently focused on tackling heroin, crack cocaine and alcohol dependency.
The authors say both chemsex drug users and health professionals may believe referral to traditional services is inappropriate.
Although some services are now developing specific chemsex and party drug clinics, the lack of data limits the advice that clinicians can give.
For instance, the National Institute for Health and Care Excellence (NICE) has provided "limited advice" on psychoactive drug use and no specific recommendations relating to chemsex drugs.
The Novel Psychoactive Treatment UK Network (Neptune), supported by the independent charity the Health Foundation, has published a guidance document for clinicians managing the "harms resulting from the use of club drugs and novel
psychoactive substances".
But more needs to be done.
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"Addressing chemsex-related morbidities should be a public health priority," the study's authors said.
"However, in England funding for specialist sexual health and drugs services is waning and commissioning for these services is complex."
Despite the different funding streams, creating centres of excellence for sexual health and drug services "could be a cost effective solution to diminished resources in both sectors".
"It could also be a source of data for further research into chemsex that would help commissioners in their decision making," they added.