Mephedrone (4mmc): Dosage, Effects, Risks and Safer Use
Learn about mephedrone (4-MMC) dosage, effects, risks and safer use. Trusted harm reduction advice to help you stay informed and reduce harm.
- What is mephedrone
- A short history of mephedrone
- What mephedrone looks like
- How mephedrone works
- The effects of mephedrone
- How to reduce the harm
- Mephedrone and the law
- Risks of different ways of using
- Long-term harm
- Overdose
- Mephedrone and chemsex
What is mephedrone
Mephedrone is a synthetic stimulant drug. It’s also known by its chemical name, 4-methylmethcathinone (4‑MMC). It is part of a group of drugs called cathinones, which are related to the natural stimulant cathinone found in the Khat plant.
People in East Africa (mainly Somalia and Ethiopia) have chewed Khat leaves for centuries. The effect is similar to caffeine and is used as a mild social stimulant.
In the UK, authorities classify the Khat plant as an illegal Class C drug.
A short history of mephedrone
Mephedrone (4‑methylmethcathinone or 4‑MMC) was first made in 1929, but it stayed under the radar for decades. In the early 2000s, underground chemists rediscovered the drug and began producing it for recreational use. They used old scientific research to recreate the cathinone-based drug and sold it online and in headshops as a “legal high” or “research chemical”. Because mephedrone wasn’t listed in the UK Misuse of Drugs Act 1971, it could be sold legally for a time, often labelled “not for human consumption” to avoid regulation.
Mephedrone became part of a wave of synthetic drugs known as legal highs, most of which were produced in China or India and sold online or in UK headshops.
To stay ahead of changing laws, underground chemists kept tweaking cathinone-like molecules. This led to the development of related drugs like methylone and MDPV (sometimes called monkey dust), which sellers often offered alongside mephedrone.
Mephedrone gained popularity in 2008 when MDMA purity dropped and ecstasy pills became less reliable. Many pills contained little or no MDMA and were instead filled with other substances, including mephedrone. People described the effects as euphoric and energetic—similar to MDMA, but shorter-lasting and more compulsive.
As use increased, so did hospital admissions and media panic. In April 2010, the UK government made mephedrone a Class B drug under the Misuse of Drugs Act. After the ban, wholesale prices jumped to around £4,000 per kilo, dealers doubled street prices, and producers were more likely to cut the drug with caffeine, glucose, MSG or mix it with other substances.
What mephedrone looks like
- Usually a white powder, visually similar to other ‘legal highs’
- Contents can vary even from the same source
- Sellers have mixed it with ketamine (‘Kit Kat’) or mis-sold crystal meth as mephedrone
How mephedrone works
Mephedrone triggers the release of noradrenaline (rush), dopamine (euphoria), and serotonin (loved-up feelings). The effects wear off quickly, often leading people to take more, increasing the risk of overuse and harm.
The effects of mephedrone
Common effects
- alertness
- elevated mood
- feeling energetic or excited
- calmness
- sociability and talkativeness
Common unpleasant effects
- dry mouth
- teeth grinding
- reduced appetite
- poor focus and short-term memory
- fast heart rate
- raised body temperature
- palpitations
- sweating
- anxiety or depression
- dilated pupils
How to reduce the harm
The safest option is not to use it. But if you do:
If you're going to use
- stick to small amounts (no more than half a gram per session)
- limit use to once a week or less
Slow and low
- take a small amount and wait
- don’t re-dose after 30–45 minutes
Stay hydrated and keep cool
- sip water, juice or isotonic drinks to stay hydrated
Avoid mixing with other drugs
- alcohol increases risk of confusion, aggression, overheating
- other stimulants increase risk of dehydration and heatstroke
Plan for the comedown
- rest, eat well, avoid alcohol
- take the next day off if needed
Mephedrone and the law
- mephedrone is a Class B drug under the Misuse of Drugs Act 1971
- possession: up to 5 years in prison
- supply or production: up to 14 years in prison
Risks of different ways of using
Swallowing
- taken in capsules, tablets, or bombed in cigarette paper
- effects start in 15–45 minutes and last 2–3 hours or more
- swallowing is likely the least harmful method
- Harm reduction: drink water to help process the drug
Snorting
- effects start in minutes and can last 3–6 hours
- can damage the inside of the nose
- Harm reduction: rinse nose with warm water between lines or after the session
Smoking
- vaporised on foil or in a glass pipe
- effects come on in seconds, last around 30 minutes
- Harm reduction: wait at least 30 minutes between hits to avoid compulsive re-dosing
⚠️ Important: Everyone reacts differently
There’s no way to know how strong any powder or pill really is. These amounts aren’t recommendations—just reports from people who use mephedrone.
Start low, go slow, and wait to see how it affects you before taking more.
Long-term harm
- strong cravings suggest possible psychological addiction
- unknown long-term risks to brain, heart or liver
- animal studies suggest possible neurotoxicity
Overdose
Mephedrone increases heart rate, blood pressure and body temperature. Taking too much can cause seizures, hallucinations or overheating.
Early signs of overdose
- sudden rise in body temperature
- red or flushed face
- hot, dry skin with no sweating
- hallucinations or confusion
- muscle cramps or stiffness
- rapid breathing or panic
What to do
- stay calm and reassure them
- encourage slow, deep breaths
- cool them down with water, loosen tight clothing
- use wet towels or ice on the neck
- if they stop sweating or collapse, call an ambulance
If unconscious
- put them in the recovery position
- stay with them and tell medics what they took
Mephedrone and Chemsex
People sometimes use mephedrone during chemsex – a term that describes sex under the influence of drugs like mephedrone, GHB/GBL, methamphetamine, or others. Many use these substances to boost energy, lower inhibitions, and prolong sexual activity.
In this situation, mephedrone is usually taken by:
- Snorting – for a fast-acting, intense rush
- Injecting ('slamming') – for a more powerful and immediate effect, but with much higher risks
- Rectal use ('booty bumping') – which avoids needles but still carries health risks
Why do people use mephedrone during chemsex?
Mephedrone increases dopamine and serotonin levels in the brain, resulting in feelings of euphoria, increased confidence, and heightened libido. These effects can feel intense and reinforcing, especially in group or party settings.
Risks linked to mephedrone in chemsex settings
- Risky sex – Mephedrone can reduce inhibitions and impair judgement, increasing the chance of condomless sex or sex with multiple partners. This raises the risk of STIs, including HIV and hepatitis C.
- Re-dosing and dependency – The effects wear off quickly, which can lead to repeated use over many hours or even days. Some people report binge patterns and dependence.
- Mental health issues – Heavy use can lead to anxiety, paranoia, and low mood once the drug wears off. Some people experience prolonged 'comedowns.'
- Injecting risks – Sharing or reusing injecting equipment increases the chance of bacterial infections, abscesses, and blood-borne viruses.
Be aware of the risks of mixing drugs
Poly-drug use is a big part of chemsex, and many people intentionally combine substances to enhance or prolong sex. But mixing drugs does increase risks, especially to your heart, mental state, and breathing.
- Mephedrone + GHB/GBL can cause confusion, overheating, and dangerous drops in consciousness
- Mephedrone + Viagra or similar meds can raise blood pressure and strain the heart
- Mephedrone + alcohol can make it harder to pace yourself or keep track of what you've taken
If you do mix:
- Start with low doses and wait between each drug; effects can come on faster or hit harder when combined
- Avoid re-dosing over long sessions without rest or food
- Keep track of what and when you've taken — or use a group note on your phone
- Make sure someone you trust is around and knows what to do if something goes wrong
- Never share injecting equipment
Harm reduction tips
- Plan: Set boundaries around what you'll take, with whom, and for how long
- Use condoms and lube to reduce the risk of STIs and injury
- Take breaks to hydrate, eat, and rest — especially if sessions last overnight or across days
- Look out for others: people can become confused, aggressive, or unwell without realising it
Share this information
Raising awareness and sharing accurate information are effective ways to reduce harm. Services can order our mephedrone information booklet to share with people who use mephedrone, or share this guide with anyone who needs to understand the risks and effects more clearly.
