The fly agaric's effects come from two small molecules: ibotenic acid and muscimol. Ibotenic acid excites nerve cells through glutamate receptors, and muscimol slows them down through GABA receptors. Psilocybin, the compound in magic mushrooms and truffles, works on a third system altogether, serotonin. That is why a fly agaric intoxication and a psilocybin trip have so little in common.
Two molecules pulling in opposite directions
Ibotenic acid is shaped like glutamate, the brain's main excitatory messenger, and activates NMDA and several other glutamate receptors. In neuroscience laboratories it is used deliberately to destroy small, targeted areas of brain tissue in animals, because overstimulated nerve cells die. That use says something about its character: it is an excitotoxin.
Muscimol is shaped like GABA, the brain's main calming messenger. It binds to GABA-A receptors at the same site as GABA itself and switches them on fully. GABA itself cannot pass from the blood into the brain, but muscimol can. Its effects are sedation, dizziness, poor coordination, distorted perception and, at higher exposure, a sleep that can deepen into unconsciousness.
Part of the ibotenic acid in the mushroom turns into muscimol by losing a carbon dioxide group, a reaction called decarboxylation, and this also happens inside the body. Both compounds leave the body quickly in urine, partly unchanged. Sources: Michelot and Melendez-Howell 2003, and the reviews summarised on Wikipedia for ibotenic acid and muscimol.
Fly agaric compared with psilocybin
| Fly agaric | Psilocybin mushrooms and truffles | |
|---|---|---|
| Active compounds | ibotenic acid, muscimol | psilocybin, converted to psilocin |
| Main target | GABA-A and glutamate receptors | serotonin 5-HT2A receptors |
| Drug class it resembles | sedatives and depressants, with an excitatory phase | classic psychedelics |
| Typical course | nausea, then drowsy dream states, sometimes agitation or confusion | visual changes and altered thinking while awake |
| Duration reported | 4 to 10 hours, sometimes up to 24 | 4 to 6 hours |
| Consistency | strength varies widely between mushrooms | varies between strains and batches |
Researchers at UC San Diego put it plainly in 2024: fly agaric works more like a depressant such as alcohol or a benzodiazepine than like psilocybin (UCSD news release). The overlap in marketing ("magic mushroom", "Amanita gummies") hides a difference in pharmacology.
Why strength is so hard to predict
The amount of ibotenic acid and muscimol in a fly agaric varies with the individual mushroom, its age, the season and where it grew. The same applies to the panther cap. Published measurements differ widely, and a mushroom gives no outward sign of how much it contains.
Processed products add their own uncertainty. When US authorities tested "mushroom" chocolates and gummies after a wave of illnesses in 2024, they found muscimol in some products, but also psilocin, a synthetic psilocybin analogue, the prescription drug pregabalin and compounds from the kava plant (FDA investigation). A small study from Virginia found unlabelled psilocybin or psilocin in four of six bags of "Amanita" gummies it tested (CDC, MMWR 2024;73:628). A label saying "Amanita" or "muscimol" tells you little about what a product actually contains.
This site does not give amounts. No number would be honest, because nobody, including the person taking it, knows what dose a given mushroom or product delivers.
Muscarine, the misnamed compound
The fly agaric gave its name to muscarine, a compound that stimulates the parasympathetic nervous system and causes sweating, salivation and tears. It was isolated from the fly agaric in 1869 and blamed for its effects for decades. The fly agaric contains too little of it to play a meaningful role. Muscarine poisoning is a real risk with other mushrooms, such as some small white Clitocybe and Inocybe species, which is one more reason that "it looked like the one in the picture" is a dangerous sentence.
Interactions
Because muscimol acts on the same receptor family as alcohol, benzodiazepines, sleeping pills and some other sedating medicines, combining them adds to the depressant effect. Poison centre reports list drowsiness deepening into coma, and patients who needed breathing support, among the severe outcomes of fly agaric and panther cap poisoning, and stacking depressants makes that more likely. If you take any prescription medicine, a pharmacist can tell you which of them act on the central nervous system.
Next: what the experience is like, the composite trip reports, or the legal status of muscimol products.
Updated