Synaesthesia and psychoactive drugs.

There are some reports that the consumption of substances like LSD or magic mushrooms may elicit conditions similar to synaesthesia. This is called "drug-induced synaesthesia" and is not genuine synaesthesia. One cannot become a synaesthete by taking drugs.
Here I would like to add the definition of the word drug: substance that can alter the functions and mechanisms of the body and brain. I am sorry, but alcohol, coffee and aspirin are drugs, too.

What do drugs cause in the brain?

For a substance to have a psychoactive effect it needs a receptor. You could picture the drug as a key and the receptor as it's lock.Our nerve cells contain a huge amount of these receptors, which by accepting neutrotransmitters or similar substances (drugs) influence the function of the brain. To have an effect, drugs need to have a structural similarity to a proper substance of the brain.

Some pairs:

In this picture you can see the similarity of serotonin and psilocin. Without this structural similarity the substance would not be able to interact with the brain receptor and therefore would not have any effects.

What does a synaesthete experience on a trip?

I guess it should be allowed to ask this question. Do psychoactive chemicals like LSD enhance or inhibit synaesthesia? There is no general answer to this, considering that there are a lot of different synaesthesias. So every synaesthete may react differently.
A synaesthete reported that the colors of music were less intensive after having consumed LSD. On the other hand he described that he was more sensitive for the smell and the taste of pictures. He also claimed that mescaline had another effect: music became very clear and very sharp.
Single statements may give an idea of the influence of drugs on synaesthesia. But there is a lack of studies.

Please note: we do not want to encourage people taking drugs. But discussing it is important.