01Principles and purposeThe professional or clinical skill and the decisions it supports.
Chemsex is a culturally specific term commonly used for planned sexual activity involving drugs such as GHB or GBL, methamphetamine and mephedrone, especially among gay, bisexual and other men who have sex with men. Ask the person what term fits. A wider sexualised-drug-use assessment avoids excluding women, trans people or others whose substances and risks may differ.
Use a non-judgemental functional history. Establish exact substances, formulations, route, dose estimate, frequency, re-dosing, combinations, injecting or rectal use, source, last use, sleep and nutrition. Ask what the drug provides, such as connection, confidence or prolonged sex, alongside harms including blackouts, dependence, missed work, debt, psychosis, assault and difficulty having sober sex.
Acute toxicity varies. GHB and GBL have a steep dose-response relationship and mixing with alcohol or other depressants increases respiratory risk. Stimulants can cause agitation, hyperthermia, cardiovascular events and psychosis. Call emergency services for reduced consciousness, abnormal breathing, seizure, chest pain or severe behavioural disturbance. Place an unconscious breathing person in the recovery position and continue observation; do not induce vomiting or assume they can sleep it off.
Dependence changes advice. A person dosing GHB or GBL around the clock may develop severe withdrawal soon after stopping, including tremor, agitation, hallucinations, delirium and seizures. Abrupt unsupervised cessation can be dangerous. Clarify last dose and withdrawal history and obtain urgent specialist or emergency assessment. Stimulant cessation can bring exhaustion, low mood and suicidality that also require support.
Sexual-health care is integrated. Ask anatomical sites and timing of exposure, condoms, trauma and injecting. Offer HIV PEP urgently for a qualifying exposure within 72 hours, and PrEP assessment for future risk. Provide site-specific STI tests, hepatitis A and B vaccination when indicated, hepatitis C testing after blood risk, contraception and emergency contraception according to anatomy and pregnancy potential.
Consent can be impaired by intoxication but drug use never transfers responsibility for assault to the victim. Ask about memory gaps, unwanted acts, covert dosing and control by partners. Offer SARC and forensic options promptly where relevant. Harm reduction can include not using alone, measuring doses, avoiding depressant combinations, spacing dosing, using sterile injecting equipment and agreeing an emergency plan, while referral addresses dependence and psychological drivers.
Key points
- Ask which substances are used, dose and route, frequency, mixing, injecting equipment, sexual context, last use, overdose, withdrawal and what the person wants to change.
- Chemsex commonly refers to planned sexual use of GHB or GBL, methamphetamine and mephedrone among gay, bisexual and other men who have sex with men, while sexualised drug risk can affect anyone.
- Treat reduced consciousness, abnormal breathing, seizure, hyperthermia, chest pain, severe agitation or psychosis as an emergency; monitor because apparent recovery may reverse.
- Never advise a person dependent on frequent GHB or GBL to stop abruptly without urgent specialist assessment because withdrawal can become severe quickly.
- Assess capacity and consent, assault, coercion, domestic abuse, self-harm and exploitation privately and without blaming drug use.
- Offer site-specific STI testing, HIV PEP within 72 hours after a qualifying exposure, PrEP for ongoing risk, hepatitis vaccination and safer-injecting supplies.
- Link sexual-health and substance services with a jointly owned plan for overdose prevention, sleep, hydration, triggers, relapse and confidential follow-up.
02Situations and prioritiesThe context, relevant information and actions that matter most.
Unrousable consciousness, snoring or irregular breathing, cyanosis or vomiting after GHB or GBL needs emergency airway and breathing support.
Dosing every few hours, waking to dose or previous hallucinations and seizures on stopping predicts dangerous withdrawal.
Hyperthermia, chest pain, severe agitation, psychosis, seizure or focal neurology after methamphetamine or mephedrone is an emergency.
Unexpected amnesia, covert administration or unwanted acts during incapacity warrants SARC, forensic-toxicology and safeguarding options.
Shared equipment, damaged veins, abscess, fever or breathlessness raises blood-borne-virus, sepsis and embolic infection concerns.
Repeated condomless exposure or shared injecting can indicate PrEP, vaccination, testing and safer-equipment needs even without symptoms.
03Assessment and interpretationHow to gather information, assess the situation and recognise uncertainty.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Substance and withdrawal timeline - Why
- Identify acute toxicity, dependence and the danger of abrupt cessation from dose, route, frequency and last use.
- Interpretation and limitations
- Frequent GHB or GBL dosing and previous withdrawal complications lower the threshold for urgent supervised care.
- 02
ABCDE and physiological monitoring - Why
- Detect respiratory depression, hyperthermia, arrhythmia, dehydration and altered consciousness.
- Interpretation and limitations
- Normal appearance between episodes does not guarantee safety because sedation and agitation can fluctuate.
- 03
Site-specific STI and HIV assessment - Why
- Test exposed anatomical sites and establish baseline and follow-up after sexual exposure.
- Interpretation and limitations
- Early negatives may fall inside diagnostic windows; PEP eligibility is a clinical decision that should not await final results.
- 04
HBV, HCV and injecting-related assessment - Why
- Identify blood-borne viruses, vaccination needs, abscess, cellulitis, bacteraemia and vascular injury.
- Interpretation and limitations
- Fever, spreading infection or systemic signs requires urgent medical care, while negative baseline serology needs timed follow-up.
- 05
Mental-health, consent and safeguarding review - Why
- Assess psychosis, suicidality, assault, exploitation, coercion and practical safety.
- Interpretation and limitations
- Use private assessment and urgent pathways when risk is current; intoxication does not negate a disclosure.
04Worked approachesCases with ordered reasoning, an action and a check of the outcome.
01Worked caseRespond to frequent GBL use safelyA patient uses GBL every two hours through multi-day sessions and wants to stop immediately at home.+
- 1Clarify last dose, current observations, prior tremor, hallucinations, seizures, delirium, concurrent depressants and whether the patient is safe now.
- 2Explain that frequent GHB or GBL dependence can cause rapidly severe withdrawal and arrange urgent supervised specialist or emergency assessment.
- 3Assess HIV, hepatitis, STI, injecting, assault and mental-health risks without delaying withdrawal care.
- 4Coordinate substance and sexual-health follow-up with an overdose plan, safer use advice and explicit ownership of test results.
02Overdose responseManage reduced consciousness as an emergencyA person becomes unrousable and breathes abnormally after GHB or GBL during sex.+
- 1Call emergency services, open the airway, assess breathing and begin basic life support if required.
- 2Use the recovery position when breathing normally, remove immediate hazards and observe continuously.
- 3Tell responders what was taken, when, how much and what else was used; preserve suspected covert-dosing evidence when safe.
03Prevention routeJoin sexual and injecting harm reductionA patient remains well but reports condomless sex and shared injecting equipment during recent sessions.+
- 1Assess whether any exposure qualifies for time-critical HIV PEP and offer emergency contraception where pregnancy is possible.
- 2Arrange site-specific STI, HIV, HBV and HCV testing with vaccination and repeat windows.
- 3Offer PrEP assessment, sterile equipment, overdose education and substance-service referral based on the patient’s goals.
05Feedback, follow-up and evidenceReview outcomes, seek feedback and identify what to improve.
- Review frequency, routes, mixing, blackouts, withdrawal signs and changes in control over use.
- Track site-specific STI and blood-borne-virus results through their diagnostic windows.
- Confirm hepatitis vaccination and HIV PEP completion or PrEP linkage where indicated.
- Reassess sleep, nutrition, mood, psychosis, suicidality, consent and exploitation after acute intoxication resolves.
- Ensure substance and sexual-health teams know who owns each follow-up action with the patient’s consent.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
A small margin can matter
GHB and GBL concentrations vary and the gap between intended effect and respiratory depression can be narrow.
Stopping may itself be dangerous
Around-the-clock GHB or GBL use can create withdrawal requiring supervised medical treatment rather than unsupported abstinence.
Intoxication never assigns blame
Impaired capacity can make sexual activity non-consensual, and responsibility remains with the person initiating it without consent.
One visit can prevent several harms
Testing, vaccination, PEP or PrEP, sterile equipment and substance support can be offered together without demanding abstinence.
07Common pitfallsFrequent interpretation and management errors.
- 01
Telling a dependent GHB or GBL user simply to stop immediately at home.
- 02
Leaving an unconscious person to sleep without airway and breathing monitoring.
- 03
Using chemsex as a label for every drug used during sex.
- 04
Making STI or substance support conditional on abstinence.
- 05
Assuming intoxication means an assault disclosure is unreliable.
- 06
Forgetting injection-site infection and hepatitis risk while focusing only on HIV.