What is 4-FA / 4-FMP?

4-Fluoroamphetamine, often called 4-FA, is a novel psychoactive substance (NPS) that belongs to the chemical group known as the phenethylamines, which also includes MDMA (ecstasy) and amphetamine (speed). Other names for 4-FA are flux, fifa, 4-fluo, 4-FMP, 4-F, 4-flava, 4-flo and 4-fluor.

Disclaimer on NPS

The information provided here is based on users’ experiences and on tentative data from research institutes that study NPS. No comprehensive studies have been done on the shorter- or longer-term effects of 4-FA. Hence, if you take 4-FA, you are your own guinea pig. So it’s important to be extra careful.


The effect of a drug depends on the characteristics of the drug itself, but also on the set and setting of the user. Here we describe the general effects of 4-FA

4-FA is a stimulant, just like MDMA (ecstasy) and amphetamine (speed). It stimulates the release of the neurotransmitters (messenger substances between brain cells) noradrenaline, dopamine and serotonin in your brain and inhibits its reuptake. As a result, these substances can no longer be taken up by the cell that released them in the first place. This ensures that there is more activation in the brain. 4-FA is excreted largely unchanged from the body.

According to most users, 4-FA is in between amphetamine and MDMA in terms of effect.

In terms of stimulation and alertness, it is very similar to amphetamine, but in terms of euphoria and empathic effects, it appears to be a milder variant of MDMA. The mind seems sharper and more alert and one tends to talk a lot. The effects of 4-FA are often perceived as more even than MDMA.

Since 2016, there has been a significant increase in the number of health incidents reported due to the use of 4-FA. These incidents vary from minor complaints such as headaches to brain haemorrhages and heart problems. There are also a few known cases of people who have died after the use of (presumably) 4-FA, but further research is needed to determine this.

Users of 4-FA cite the following positive effects and unpleasant side effects:

Positive effecten (negative) Side effects

More intense music experiences

Music can be experienced louder or more intense. For example, it can feel as if you are completely ‘absorbed’ in the music or that you feel the low tones from the music go through your body more intensely.

Dose and route of administration

4-FA is usually swallowed, both in pill and powder form, but also exists as a viscous liquid. The powder is often put in a capsule or in a rolling paper (‘bomb’). But it can also be dissolved in a drink.

When snorting, the 4-FA enters the blood via the nasal mucosa and you experience the effects within a few minutes. This route of administration is harmful to your nasal mucosa. In addition, people experience it as more painful than snorting amphetamines, for example.

The higher the dose, the more intense the effect and the longer the effect lasts. What a dosage is at which you mainly experience desired effects also depends on what is desired for you, any sensitivity to the substance, your body weight, experience and your mood.

If you are using it for the first time, first take a very low dose to see how you react to it and build up that dose a little later. Taking your dose spread over the day/evening seems to make it more difficult to sleep (even the second night after use) and it does not always give more desired effects. In addition, the side effects are greatly increased. Subsequent doses often come in harder than the first dose.

The amount of 4-FA in pills and powders can vary greatly. It may also contain other substances. You can’t tell by the appearance of a pill or powder. In 2018 and 2019, the most popular 4-FA substitute according to the test service was 4-FMA (4-fluoromethamphetamine). In terms of effect, 4-FMA is fairly similar to 4-FA, both in terms of desirable and undesirable effects. The risks of 4-FA could therefore also apply to 4-FMA. But because 4-FMA is even less known than 4-FA, the phrase “You are your own guinea pig” is even more applicable to the use of 4-FMA.

Information about dosing can only be based on the experiences of users of 4-FA at this time.

Doses for swallowing
Low 40 – 75 mg
Medium 75 – 125 mg
High 125+ mg


When you take 4-FA, the first effects appear after 20-60 minutes. If you have eaten beforehand, it can take longer before you notice the effects! The effects last about 4 to 6 hours in total. But there are also people who still feel the effect up to 12 hours after taking it. When you snort it, you feel the effects within minutes and it wears off faster.


A major risk of 4-FA use is that the symptoms experienced, such as headache or a slight increase in blood pressure, are mild in the beginning, but can quickly turn into life-threatening situations, including brain haemorrhages and heart problems. In 2016, 2 deaths were even reported in which 4-FA was found in the blood. The tricky part for the emergency room is that if you’ve taken 4-FA, they can’t estimate whether your headache is going to become a serious problem or if nothing is wrong.

The risk of serious problems always depends on the composition of the drugs, your own sensitivity, your health and your behavior. The environment also has an influence. How much do you drink? How much do you move? How warm is it? Do you use several drugs at the same time? How much did you take?

The more and the more often you use 4-FA, the greater the chance of risks. 4-FA has not been used very long and therefore no long-term risks are known yet. Because the effects are similar to MDMA and speed, the long-term risks may also be similar, but we don’t know for sure. Long-term risks of MDMA and speed are:

Short term risks

Long term risks


Combining different types of drugs can be risky and unpredictable. When you combine drugs you can have a higher risk of health problems. In the following paragraphs you can read about the effects and the risks of a number of combinations that occur frequently and also a about few that are extra hazardous. Also check our theme combining drugs.

4-FA and alcohol

Using 4-FA makes you feel awake and cheerful. As a result, you may feel the sedating effects of the alcohol less and you may tend to drink more alcohol. Be careful, because this can cause an extra large hangover. So do not drink alcohol while taking 4-FA or make an agreement in advance with yourself or your friends how many glasses of alcohol you want to drink. This prevents headaches the next day and is better for your health!

4-FA and cannabis

Sometimes people use cannabis after or while using 4-FA to calm down or fall asleep more easily. Cannabis can soften the stimulant effects, especially at the end of the rush. However, this is not recommended for everyone, some people may feel anxious or restless. If you suffer from insomnia after using 4-FA, it is advisable to time your use better. Keep in mind what time you want to go to sleep and do not take any more about 12 hours before you want to go to sleep.

4-FA and ecstasy/MDMA

Some people use MDMA when they notice that the effects of the 4-FA are fading away. By combining they prolong the euphoric high. Redosing 4-FA just ensures that you stay awake longer. It hardly increases the euphoria. That is why MDMA is chosen. If you choose to combine, take less of both drugs than if you were taking only 1 drug.
Both are stimulants. The combination increases the load on the heart and blood vessels. 4-FA has an unpredictable effect on blood pressure in some people. It can get way too high. In combination with MDMA, this blood pressure can become even higher.
Combining MDMA and speed increases the risk of brain damage. This is probably also the case with 4-FA and MDMA.

Unity tips

  • Even a low dose can cause problems in people who are sensitive to 4-FA. If you are using 4-FA for the first time, take a low dose first to see how you react to it.
  • Both users and experts advise against a dosage above 150 mg. The effects are severe, the risk of side effects increases from 100 mg and the risk of serious overheating, among other things, increases sharply with a dose of 150 mg.
  • Therefore, always have your drugs tested and weigh the powder well beforehand. Use a scale that can weigh milligrams. Check drugs-test.nl for addresses, opening times and conditions.
  • Because the effects of 4-FA start more slowly than with MDMA and amphetamine, you may be tempted to take it. This can lead to overdose. Therefore, keep your use at 1 dose.
  • Rest every hour. Do not wear warm clothes and do not put on a hat, cap or hat inside.
  • Do not drink more than 1 glass of soda or water per hour. This is enough to stay hydrated and prevent water intoxication. Keep track of how much you drink during a party in your phone.
  • Eat healthy before, during and after you use 4-FA and get enough rest. If you are very tired or suffer from insomnia, do not use 4-FA! Also, make sure you get enough antioxidants and vitamins through fruits and vegetables.


How do you dose powder or capsules?

To be able to weigh a certain dose properly, you need a good scale. Have a scale that can weigh milligrams, to 3 decimal places (0.001 mg). A scale that weighs 0.01 (2 decimal places) may be just accurate enough for MDMA, but not for many other substances.

Where can you find such a scale?

On the large international online webshops you can find scales for around 20 euros that can weigh 3 figures after the decimal point. You can buy empty capsules in different sizes at pharmacies, smart shops or drugstores. Some are also suitable for vegetarians. You can write the drug and dosage on the capsule with a waterproof marker or a CD marker.

How did the use of 4-FA start?

Although scientific studies have been conducted with this drug as early as 1975, 4-FA has been available on the recreational drug market since approximately 2005. On the testing service we see 4-FA since about 2007. It was initially mainly sold as speed or ecstasy. But as of 2012, 4-FA is increasingly brought to the testing service as 4-FA and is sold less and less as anything else. Since 2012, Unity has also been asked more questions about 4-FA. The popularity of the drug therefore seems to be increasing considerably. This is confirmed by a survey by the Trimbos Institute among frequent goers (the large nightlife survey). Of the frequent partygoers surveyed, 10% indicated that they had used 4-FA at some point. This makes 4-FA the most commonly used NPS (new psychoactive substance).

Demand has decreased since the warning in 2016 from the Trimbos Institute, Unity and various addiction care facilities. 4-FA can lead to brain hemorrhages. Since that warning, the drug’s popularity has declined. There is still a small number of people who prefer 4-FA over other drugs.

I want to combine 4-FA with other drugs. Is that a good idea?

Combining drugs can be risky. The effects are often unpredictable. You are more at risk of health problems. Little is known about the combination of 4-FA with other drugs.

4-FA with uppers

Increases the risk of worsening side effects. 4-FA does something weird to your blood pressure. We don’t know exactly what yet. But if you combine it with other uppers, there is a greater chance that your blood pressure will become very high or that the risks of 4-FA increase, for example extreme headaches.
The combination with MDMA increases the risk of brain damage and overheating.

4-FA with downers

Due to the stimulating effect of 4-FA, you may notice the effects of downers less. There is a chance that you will take more downers to feel those effects. Or that you are going to take more 4-FA because you notice less of the 4-FA.

I am planning to combine 4-FA with speed and/or ecstasy (MDMA). What are the consequences?

4-FA is a stimulant that can cause complaints on your cardiovascular system. This risk is increased by combining it with other stimulants such as speed or MDMA. The effects reinforce each other and because 4-FA continues to work for a long time, you increase the risk of unpleasant side effects and risks such as: tight jaws, muscle tension, heart palpitations, pressure on the chest, sleeping problems, a strong hangover and hangover the days after. You are also more likely to suffer from severe headaches.

I am planning to combine 4-FA with alcohol. What are the consequences?

Alcohol dampens the effect of 4-FA and blurs your boundaries. As a result, you may take more 4-FA. Or you think you can drink more. You are also more likely to experience headaches and nausea.

I am planning to combine 4-FA with GHB. What are the consequences?

4-FA is sometimes combined with GHB to take the edge off 4-FA. The risk of this is that you will not feel the anesthetic effect of GHB due to the stimulating effect of 4-FA, which increases the chance of overdosing with GHB. If you then take too much GHB, your body is still stimulated, but you are no longer or not fully conscious. That can look very intense. Someone then moves very strangely and it is not possible (any longer) to make contact.

How does 4-FA affect your sleep?

4-FA is an upper and has a stimulating effect on the body. As a result, you can sometimes not sleep for hours after use, we also call this “a ceiling shift”. Although translated to English it sounds a bit weird 😉 You lie in your bed and look at the ceiling because you can’t sleep. Why can’t you sleep? And if you do manage to fall asleep after stimulants, how well do you sleep? Read that in the article How do you rest after stimulants?

What about the law and 4-FA?

In the Netherlands, 4-FA did not fall under the Opium Act until May 25, 2017. If you were caught by security or police, you were therefore not legally punishable. As of May 25, 2017, 4-FA is on list I of the Opium Act and possession and trade of 4-FA is punishable. It is therefore just as illegal as MDMA, for example.

Are 4-FMA and 4-FA/4-FMP the same substance?

No, these are different substances. 4-FA (also called 4-FMP) is the abbreviation of 4-fluoroamphetamine. 4-FMA is the abbreviation of 4-fluoromethamphetamine! So they are chemically different substances that also have a different effect on you. The molecules are not very different from each other, so the effects are similar. 4-FMA is sometimes sold as 4-FA on the black market. To be sure what is in your powder, have it tested at the testing service!

Are the risks of 4-FMA bigger than those of 4-FA?

Little is known about the risks of 4-FMA. It is then safer to assume that the risks are greater, until it is clear what the risks are. Get your drugs tested to make sure it’s actually 4-FMA. 4-FMA is stronger than 4-FA. This means that you need less to get an effect. Keep this in mind with your dose. The use of a scale is recommended.

What to do if someone has a bad trip?

Always make sure that you are and remain safe yourself. If you are in danger, you cannot help the person in need.
Find a quiet place with the one who is having a hard time. Don’t try to deny that he/she is having a bad trip. Try to reassure him/her: he/she has taken drugs and the effects and thus the bad trip always wear off. Ask the person about what they are experiencing and try to talk the trip on a positive side without downplaying it. For example, by giving a positive meaning to the things he/she sees. Try to do things that make him/her feel comfortable, such as moving or singing. See if it makes sense to talk about pleasant things. Distraction can also help, for example by drawing. Let your voice sound calm and reassuring.
Make sure that the user does not end up in dangerous situations such as traffic. Call emergency services if it becomes unsafe for the user or his environment or if the bad trip is too intense to solve it yourself.

What if I have medical complaints after the use of partydrugs?

Some complaints after using drugs can last longer, A medical explanation or even treatment may then be necessary. The Brijder has set up a national consultancy for party drugs related medical complaints. If you have medical complaints after the use of party drugs, you can call the consultancy: 088 – 358 29 40. This service is only available in the Netherlands.


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Combined use

Combining different substances carries extra risks. It produces unpredictable effects and there is a greater risk of health problems. Little is currently known about the effects of combining 4-FA with other psychoactive substances.

Speed and/or ecstasy in combination with 4-FA

4-FA is a stimulant drug, which can cause cardiovascular problems. That risk is aggravated if you combine 4-FA with other stimulants like speed or ecstasy. Effects may reinforce one another, and because the effects of 4-FA persist relatively long, there is a greater risk of unpleasant side-effects like ‘jacked up’ behaviour, stiff jaws, tense muscles, heart palpitations, pressure on the chest, sleep disturbances, and wicked hangovers and crashes

Alcohol in combination

Alcohol subdues the effects of 4-FA and blurs your limits. You may get the urge to take extra 4-FA or to drink more alcohol. Alcohol also heightens the chances of headaches and nausea.

GHB in combination

Some people take GHB to temper the stimulant effects of 4-FA. The anaesthetic effects of GHB may then get camouflaged by the stimulant effects of 4-FA, increasing the risk of a GHB overdose.

Unity tip: Don’t take 4-FA if you have diabetes, heart problems, blood pressure problems or psychological problems. Also avoid 4-FA if you are pregnant, suffer from migraines or epilepsy, or are taking medicines.

The law

On May 25th 2017 4-FA was placed on Schedule I (the list of hard drugs) of the Opium Act. This means it has been classed as an illegal drug and possession, trade and production of 4-FA is illegal.

It is against the law to take part in road traffic whilst under the influence of drugs. It is also dangerous, both to you and to other road users. Clubs, raves and festivals have zero-tolerance policies in place. Because police and security workers cannot recognise what drugs you are carrying, you may be refused entry or even handed over to police if you are caught in possession of 4-FA. 

Taking 4-FA is never without risk! By carefully reading the information and advice in this leaflet and heeding the tips provided by Unity, you can limit the side-effects and health risks of the use of 4-FA as much as possible.