Chemsex is sexual intercourse between people under the planned influence of psychoactive substances. Substances such as GHB/GBL, mephedrone, ketamine, methamphetamine (crystal), poppers, cocaine or amphetamine are used particularly frequently for this purpose. The term chemsex originates from the international gay scene and is also widespread in Switzerland. Often, private meetings are arranged via social media (dating apps) in order to have (semi-)anonymous sex with targeted use of psychoactive substances and potency-enhancing agents. 

Even if psychoactive substances are mainly used for sex, after longer periods of use without rest, sensory illusions (visual and acoustic hallucinations), anxiety and paranoia (acute psychotic states) can occur. Therefore, it is best to take a break of several weeks between consumption days so that body and mind can recover sufficiently. Make sure you eat a balanced diet and get enough sleep.

If sex is practised very frequently under the influence of substances, there is a risk that sex without the influence of substances loses its appeal or is no longer possible (including a lack of libido).


Chemsex usually takes place at (semi-) private sex parties, which often last several days. Such sex parties are often organised through friends and online platforms such as Grindr.


Slamming is the intravenous use of psychoactive substances.

Slamming is particularly dangerous because the effect of the respective substance is immediate and therefore the risk of overdose and the development of dependence is greater than with other forms of application such as sniffing, swallowing or smoking. In the case of intravenous use, there is a massively increased risk of contracting HIV and hepatitis C if syringes are shared.

Make sure you are in a suitable environment and only use when you feel comfortable. Think carefully about who you are slamming with and whether you can imagine being injected by that person. Always use your own syringe, needle and swab.

Hygiene is important: use a tourniquet, alcohol swabs and a new sterile syringe and needle for each injection. Important: Everyone uses their own syringe, so never pass syringes on! This way you can prevent the risk of a hepatitis C infection or an HIV infection.

If you feel that you cannot breathe after the injection and have a strong urge to cough, sit upright and hold up the arm that was injected. Press a clean handkerchief firmly on the injection site.

It is gentler on the veins if you take the dose "up your bum" (inject behind the sphincter without a needle). The potency remains the same, only the onset of action is delayed - and it is gentler on the circulation than slamming. Oral or nasal consumption would also be less harmful to health. 


The safer use messages as well as drug, set and setting should be taken into account for every use of psychoactive substances. This also applies (especially) to sex parties, where consumption takes place over longer periods of time, with partly unknown persons and by means of dangerous forms of consumption (slamming).

Psychoactive substances can influence your safer sex behaviour. Increased risk-taking and suppression of pain increase the likelihood of long, hard 'sessions', which may not involve the use of condoms or gloves (for fisting) and may put a lot of strain on mucous membranes. The risk of HIV, hepatitis and other infections is high.

During long sessions, it is easy to forget to take HIV medication, which can lead to resistance to the medication. This may require a change of therapy over a longer period of time.

More information on interactions between HIV medication and various psychoactive substances

The effects caused by a combination of two or more substances are difficult to assess and usually do not correspond to the sum of the individual effects. Mixing involves additional high health risks. Depending on the substance, the respective effects intensify (sometimes many times over), or they influence the body and psyche in different directions.

Further information

Information on Chemsex:
Friday/Monday (English)

I know what I am doing. Gay sex and gay life

Counselling centres:
Checkpoint Zurich

Arud Centre for Addiction Medicine