Muscimol vs Ibotenic Acid: How Drying Changes Fly Agaric

Muscimol and ibotenic acid are the two main psychoactive compounds in fly agaric (Amanita muscaria). Ibotenic acid excites nerve cells through glutamate receptors. Muscimol damps them down through GABA-A receptors. Drying and heating turn some ibotenic acid into muscimol, so processing changes the mushroom's chemistry. It does not make it safe.

This page replaces an older post that listed "benefits" and gave dosing advice. Neither was supported by evidence, and both have been removed. What follows is the chemistry, and why the balance between the two compounds matters for toxicity.

What are muscimol and ibotenic acid?

Both are small isoxazole compounds found in the cap and stem. They are closely related, but they push the brain in opposite directions (Michelot & Melendez-Howell, Mycological Research, 2003).

• Ibotenic acid is an excitatory amino acid. It resembles glutamate, the brain's main "go" signal, and activates NMDA glutamate receptors. Neuroscientists inject it into animal brains to destroy nerve cells in a precise area. It is a standard lesioning tool.
• Muscimol has a shape very like GABA, the brain's main "stop" signal. It is a potent agonist at GABA-A receptors. Researchers inject it to switch off a brain region temporarily.

Both descriptions come from the US Food and Drug Administration's 2024 review of the published literature (FDA Scientific Memorandum on Amanita muscaria, September 2024). Its authors classed both compounds, along with muscarine, as having "high toxicological potential" based on structure and metabolism data. For more on muscimol's receptor selectivity, see why muscimol is not a generic GABA-A agonist.

How does ibotenic acid become muscimol?

The change is called decarboxylation. Ibotenic acid loses its carboxyl group as carbon dioxide, and what is left is muscimol. This can happen in three settings.

During drying. A Japanese food-safety study measured both compounds before and after processing. Sun-drying and heat-drying lost much of the ibotenic acid and raised the muscimol content. The authors concluded that processing would intensify the mushroom's toxicity (Tsunoda et al., Journal of the Food Hygienic Society of Japan, 1993).

During cooking. In the same study, heat raised muscimol and lowered ibotenic acid. The shift was larger in acidic conditions. But ordinary cooking of up to 10 minutes hardly reduced the toxic compounds overall. Boiling or soaking moved most of both compounds into the water, which removes them from the solids but does not destroy them.

In the body. The FDA memorandum notes research suggesting that some ibotenic acid may convert to muscimol after it is eaten. Both compounds cross into the brain.

Storage changed little. Dry or salted samples stayed stable in the 1993 study.

Why does the ratio between them matter?

Because the two compounds pull in opposite directions, the mix shapes what poisoning looks like. The FDA memorandum describes patients who swing between sedation and severe agitation, which it links to combined GABA and glutamate activity. It names muscimol as the likely driver of the major clinical signs.

A 2025 review adds that dried mushrooms behave differently from fresh ones. Part of the ibotenic acid has already converted into muscimol, which the authors describe as a potent GABA-A agonist that readily crosses into the brain (Stoeva-Grigorova et al., Toxins, 2025). So "fully converted" is not a safety label. It describes a product in which the more potent compound dominates.

Natural variation makes this harder still. Figures cited by the FDA from Japanese forensic testing put muscimol in caps at 46–1,203 ppm and ibotenic acid at 182–1,839 ppm. That is a more than twentyfold range for muscimol alone. You cannot tell where a given mushroom sits by looking at it. Our article on what lab analysis shows about fly agaric potency covers this in more detail.

What the chemistry does not tell you

Muscimol's pharmacology is well studied in the lab. That is not the same as evidence of a benefit from eating it. The FDA review found no toxicity studies sufficient to establish safe use of the mushroom or its compounds in food. In December 2024 the agency told manufacturers that A. muscaria, muscimol and ibotenic acid are not authorised as ingredients in conventional food (FDA constituent update, 18 December 2024).

The clinical research the FDA did find involved muscimol infused directly into the brain in epilepsy studies. That is not oral use, and it does not show that eating the mushroom helps anyone. Australia's medicines regulator went further. In 2023 it added ibotenic acid to Schedule 9 alongside muscimol and described muscimol as a "psychedelic neurotoxin" (TGA notice of final decisions, 15 December 2023). For the wider chemistry, see why ibotenic acid is a neuroscience research standard.

Frequently Asked Questions

Is muscimol safer than ibotenic acid?

No. The FDA's 2024 review names muscimol as the likely driver of the major signs of fly agaric poisoning. Converting ibotenic acid into muscimol changes the risk; it does not remove it.

Does drying convert all the ibotenic acid into muscimol?

No. A 1993 study found that sun- and heat-drying lost much of the ibotenic acid and raised muscimol, but conversion is partial and varies. Starting levels also vary more than twentyfold between mushrooms.

Does boiling remove the toxins?

Boiling or soaking moves most of both compounds into the water, but it does not destroy them. The same 1993 study found that ordinary cooking of up to 10 minutes hardly reduced them, and the FDA notes toxic compounds were still measurable after boiling.

Is muscimol approved for use in food or supplements?

Not in the US or Australia. In December 2024 the FDA said muscimol, ibotenic acid and A. muscaria are not authorised in conventional food and that it is evaluating their use in dietary supplements. Australia lists both compounds in Schedule 9.

Does muscimol have proven health benefits?

No. There are no controlled human trials showing a benefit from eating fly agaric or muscimol. The research use of muscimol involves direct infusion into the brain, not oral use.

Disclaimer: This article is for education only. It is not medical or legal advice. Amanita muscaria is toxic, and it is not sold for ingestion. If someone may have eaten it, contact a poison centre or your local emergency number.