The term “Chemsex” is used in the United Kingdom to describe intentional sex under the influence of psychoactive drugs, mostly among men who have sex with men. The main drugs are mephedrone, γ-hydroxybutyrate (GHB), γ-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.

Mephedrone and crystal meth are physiological stimulants, increasing heart rate and blood pressure, as well as triggering euphoria and sexual arousal. GHB (and its precursor GBL) is a powerful psychological disinhibitor and also a mild anaesthetic.

Anecdotal reports and some small qualitative studies in the UK find that people engaging in chemsex report better sex, with these drugs reducing inhibitions and increasing pleasure.

Unfortunately use of chemsex can lead to mental health problems which can be permanent. Moreover Casual sex, particularly if under the influence of alcohol or drugs can lead to the acquisition of sexually transmitted infections and even such bugs as shigella, an infection causing severe bacillary dysentery and diarrhoea usually associated with travel to regions such as Indian subcontinent, North and East Africa and South America.

See trailer for Chemsex, a film ChemsexOfficial directed by William Fairman and Max Gogarty (a Peccadillo Pictures)  in the medical journal Lancet.