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

Energetic feeling

You have feelings of being energized. Sitting still is sometimes more difficult and this energetic feeling is often expressed through the urge to dance or move.

Head ache

Head ache

Euphoria, feelings of love

This substance can make you feel euphoric, like you are in love. You feel comfortable in your own skin and can experience things as pleasant more quickly.

Pressure on the chest / heart palpitations

Pressure on the chest / heart palpitations


Strong sense of connectedness to others or your environment. You can connect more easily with others and notice less inhibitions than you might normally experience in social contact. For example, it may be easier to speak openly about the things that are bothering you.

Increase in blood pressure and heart rate

Due to increased cardiac stimulation, heart rate and blood pressure rise.

Need for contact, conversation and intimacy

Having a good conversation with someone, or cuddling, can be very pleasant and interesting.

Increased body temperature

Stimulants cause increased activity in muscles, and increase the “base temperature” of the body. This causes the body temperature to increase.

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.


Some drugs keep you from falling asleep. Stimulants often have this effect, but even after using psychedelics or downers, sleep is disrupted and it is possible that you can’t sleep.

Desire to move

You can get a strong desire to dance and move around and dance. This might mean it can be difficult to sit still.

Decreased appetite

Stimulation of the fight-or-flight response in the body can suppress appetite.

More intense experience of touch

Physical/physical contact with other people feels different or more intense than usual. Giving a hug to someone else can be very pleasant. It can also happen that you prefer not to touch others because this can be too intense. This effect can therefore be both positive and negative.

Jaw clenching

Increased muscle tension can cause the jaws to clench together. As a result, the teeth are firmly pressed together and it is possible to bite your tongue and/or cheeks.

Teeth grinding

Grinding your teeth

Increased sweating

In response to the increased stimulation and changes in body temperature, the skin will start to secrete sweat to cool the body temperature back to normal levels.


Forgetfulness. Short term, failure to remember events shortly after ingestion.

Confusion and restlessness

Confusion and restlessness


Easily annoyed or irritated.

Paranoia and delusions

Anxiety, paranoia and delusions (e.g. the idea that people are talking about you).


An uneasy and tense feeling in the abdomen, which may cause discomfort. Nausea often precedes vomiting.

Difficulty reading

It can be difficult to read texts. This is most noticeable with small text, such as on a phone.

Dry mouth

Stimulation of sympathetic pathways decrease saliva production, this causes the mouth to feel dry.

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


This substance can cause fainting.

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.

Read more



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.