Griffonia has an unusual characteristic for a plant: its risk depends almost not at all on the dose, but on what you take alongside it. In a person without treatment, 5-HTP is well tolerated, and its main drawback is nausea that can be managed by increasing slowly. In a person taking an antidepressant, tramadol, or triptan, the same capsule changes in nature.
This article covers everything comprehensively: what trials have measured in terms of dropouts and adverse effects, what exactly serotonin syndrome is and how to recognize it, the precise list of incompatible medications, data on pregnancy, the two historical cases of the peak X and scleroderma under carbidopa, a case of massive overdose, and what is known about long-term tolerance.
The common risk. Nausea, dose-dependent: in a trial combining 5-HTP and carbidopa, dropouts due to adverse effects increased from 6.6% at 100 mg to 45.5% at 300 mg. It results from the conversion of 5-HTP to serotonin in the intestine, and can be managed by increasing slowly and taking capsules with meals.
The serious risk. Serotonin syndrome, from combining with another serotonergic agent: antidepressants, tramadol, triptans, lithium, linezolid, dextromethorphan, St. John's wort, levodopa. One case has been published with linezolid. The exclusions. Pregnancy, breastfeeding, children outside of medical prescription. The historical cases. Peak X, a family of contaminants identified in several commercial 5-HTP products, which makes purity a safety criterion, and a case of scleroderma at high doses with carbidopa in 1980. The liver and kidneys. No signal: one year of high-dose 5-HTP in rats with no abnormalities.
Common side effects and how to avoid them
Fifteen healthy volunteers received 100, 200, or 300 mg of 5-HTP combined with carbidopa, or placebo, in increasing doses. Hormonal responses increased with dose, but so did nausea and vomiting: the dropout rate due to adverse effects was 6.6% at 100 mg and 45.5% at 300 mg. The authors conclude that the frequency of nausea limits the use of doses above 100 mg in this protocol.
Smarius LJCA, Jacobs GE, Hoeberechts-Lefrandt DHM, et al. J Psychopharmacol 2008;22(4):426-433. DOI: 10.1177/0269881107082025
Important clarification: these trials combined 5-HTP with carbidopa, which increases exposure fifteenfold and makes the comparison severe compared to a supplement taken alone. An earlier trial from the same center measured that 100 mg of 5-HTP with carbidopa produced an area under the curve 15.4 times higher than 100 mg without carbidopa, and that only the combination triggered nausea. A griffonia extract without carbidopa is therefore better tolerated; the dose-dependent logic, however, remains the same.
| Effect | Frequency | What explains it | What helps |
|---|---|---|---|
| Nausea | Most frequent, increases with dose | Conversion of 5-HTP to serotonin in the intestine | Escalate gradually, take with meals, divide doses |
| Vomiting | Especially at high doses | Same mechanism, greater intensity | Step down or discontinue |
| Dizziness, fatigue | Reported in earlier trials | Central serotonergic effect | Take in the evening, avoid night driving initially |
| Very vivid dreams | Variable from person to person | Increased REM sleep, measured by polysomnography | Reduce the dose or take it earlier |
| Loose stools | Occasional | Intestinal serotonin and digestive motility | Split the dose |
Serotonin syndrome: what it really is
Serotonin syndrome is a potentially life-threatening reaction whose manifestations range from mild adverse effects to severe toxicity. It results from excessive stimulation of serotonin receptors by serotonergic drugs, either through therapeutic use or overdose of a single agent, or through interaction between multiple agents. Its central features combine neuromuscular excitation, dysfunction of the autonomic nervous system, and altered mental status in a patient whose serotonergic treatment has just been introduced or modified. Early recognition and management are decisive.
Mikkelsen N, Damkier P, Pedersen SA. Basic Clin Pharmacol Toxicol 2023;133(2):124-129. DOI: 10.1111/bcpt.13912
Neuromuscular excitation: tremors, involuntary muscle contractions, exaggerated reflexes, rigidity.
Autonomic nervous system: fever, profuse sweating, rapid heart rate, unstable blood pressure, diarrhea, dilated pupils.
Mental status: agitation, unusual anxiety, confusion.
These signs typically appear within hours of introducing, increasing, or combining a serotonergic product. In their presence, stop and consult without delay, reporting everything you are taking, supplements included.
A published case illustrates the mechanism: a man in his sixties treated with linezolid, an antibiotic with monoamine oxidase inhibitor properties, self-administered 5-HTP for low mood; he developed serotonin syndrome requiring intensive care hospitalization. The message is not that 5-HTP is dangerous, but that serotonergic self-medication in parallel with a prescription is. Another trial showed that fluoxetine markedly potentiates the hormonal response to 5-HTP, unlike tricyclics: pharmacological proof that the two act on the same mechanism.
The list of drugs not to combine
| Class | Examples | Why |
|---|---|---|
| SSRIs and SNRIs antidepressants | Fluoxetine, sertraline, paroxetine, escitalopram, venlafaxine, duloxetine | Same serotonergic pathway, potentiated effect demonstrated |
| Tricyclic antidepressants and MAOIs | Amitriptyline, clomipramine, moclobemide, selegiline | Cumulative serotonergic burden |
| Opioid analgesics | Tramadol, tapentadol, fentanyl | Intrinsic serotonergic action |
| Migraine triptans | Sumatriptan, rizatriptan, zolmitriptan | Serotonergic receptor agonists |
| Antibiotic | Linezolid | Monoamine oxidase inhibitor, one case reported with 5-HTP |
| Antitussive | Dextromethorphan, found in over-the-counter cough syrups | Serotonergic properties |
| Mood regulator | Lithium | Amplifies serotonergic transmission |
| Parkinson's treatments | Levodopa, carbidopa, benserazide | Carbidopa increases 5-HTP exposure 15-fold |
| Plant | St. John's Wort | Serotonergic, and enzyme inducer |
You don't need to memorize this list. Simply ask your pharmacist before buying: "I'm taking this, can I take a supplement that increases serotonin?" If you don't take any regular medication and you're neither pregnant nor breastfeeding, there's no question to ask.
Pregnancy, breastfeeding, children
In 1,115 women followed from the first trimester with repeated three-dimensional ultrasounds, higher maternal 5-HTP concentrations between 7 and 11 weeks of pregnancy were associated with reduced embryonic growth, lower estimated fetal weight and birth weight, and increased risk of small for gestational age. Conversely, higher kynurenine concentrations were associated with reduced risk.
van Zundert SKM, van Egmond NCM, van Rossem L, et al. Hum Reprod 2024;39(5):912-922. DOI: 10.1093/humrep/deae046
This study concerns 5-HTP produced by the body, not supplementation, and it is an observed association, not a demonstrated cause-and-effect relationship. It therefore does not prove that a supplement would harm pregnancy. But in a context where no safety trial exists in pregnant women, where serotonin plays a role in embryonic development and where laboratory studies show 5-HTP toxicity in cellular models of embryos, abstinence is warranted. There is also no data during breastfeeding.
In children, data exist, and they are even positive: the trial on night terrors, the pediatric migraine trials. All were conducted under medical supervision, with doses adjusted for weight. An adult supplement has no place in a family medicine cabinet.
The two historical cases: Peak X and scleroderma
Eosinophilia-myalgia and Peak X
In 1989, an epidemic of eosinophilia-myalgia syndrome struck the United States. It was attributed not to tryptophan itself but to contaminated batches from a single manufacturer. Tryptophan was withdrawn from the market and replaced by 5-HTP, produced differently. In 1994, an FDA team described a family in which one member developed eosinophilia-myalgia syndrome and two others developed eosinophilia after exposure to 5-HTP containing an impurity absent from other samples; replacement with 5-HTP without this impurity caused the blood abnormality to disappear.
Mass spectrometry analyses subsequently showed that this contaminant, named peak X, was actually a family of molecules of identical mass, found in eight commercial samples analyzed at that time, and whose main component was identified as tryptophan-dione, a presumed neurotoxic compound. No cases of the syndrome were reported with these commercial batches, whose contamination levels were far below that of the incriminated batch, but the finding remains: the purity of an extract is not guaranteed, it must be controlled.
This is why the displayed percentage, the origin, and analyses documented by the manufacturer are not marketing arguments but safety criteria. A standardized, traceable, and controlled extract is not the same thing as a lowest-price powder, even when the label displays the same molecule.
Scleroderma with carbidopa
In 1980, the New England Journal of Medicine published the case of a patient treated with high doses of L-5-HTP combined with carbidopa for intention myoclonus, who developed a disease resembling scleroderma, with elevated kynurenine levels. The authors found elevated kynurenine in seven out of fifteen patients with idiopathic scleroderma, but not in eight other patients treated with the same combination without developing the disease. The context is one of medical use at doses far exceeding those of a supplement, with a drug combination and probably individual susceptibility. No comparable signal has been reported with griffonia extract at usual doses.
Overdose and long-term tolerance
A healthy 44-year-old man ingested ten times the recommended dose of 5-HTP powder. Four hours later, he presented marked anterograde and retrograde amnesia, disorientation and confusion, without loss of consciousness, without seizure, and without signs of serotonergic toxicity. Brain imaging on day 2 showed bilateral and symmetric diffusion restriction of the hippocampi, suggestive of ischemia. Memory improved sufficiently for return to work at two months, and imaging was normal at eleven months.
Nash E, Jamshidi N. Clin Neurol Neurosurg 2022;220:107384. DOI: 10.1016/j.clineuro.2022.107384
This isolated case reminds us that a supplement is not inherently harmless, and that the recommended dose is not a decorative figure. In dogs, 5-HTP is indeed a classic cause of poisoning: a series of 21 cases reports signs resembling human serotonin syndrome, with a minimum toxic dose of approximately 24 mg per kilogram, which explains why a bottle must be kept out of reach of both animals and children.
Conversely, prolonged exposure at reasonable doses shows no concerning signal. A study of chronic toxicity in 120 rats divided into three groups, one receiving a high dose of 5-HTP in drinking water for one year, found no difference in weight, no hematological, hepatic or renal abnormalities, no eosinophil infiltration or tissue inflammation, the only difference being lower systolic blood pressure in the treated groups. In humans, no trial has exceeded twelve weeks, which remains the honest limit of our knowledge.
The checklist before you start
120 capsules of seed extract from Griffonia simplicifolia standardized to 30% 5-HTP, or 90 mg of 5-HTP per capsule: a readable dose to start low and adjust. HPMC vegetable capsule, additive-free, manufactured in France, 30-day treatment.
See Griffonia (5-HTP)Not recommended for pregnant and breastfeeding women and people on antidepressant treatment. Do not exceed the recommended dose.
Frequently asked questions
Side effects
Is griffonia dangerous?
At trial doses and in a person without treatment, griffonia is well tolerated: reported side effects are mainly digestive and transient. The real danger does not come from the plant but from three situations: combination with a serotonergic medication, pregnancy, and massive overdose. This is why the question to ask yourself before buying is not the dose but your list of treatments.
What are the side effects of 5-HTP?
Nausea comes largely at the top, followed by vomiting, dizziness, and fatigue. These effects are dose-dependent: in a trial with carbidopa, withdrawals for adverse effects went from 6.6% at 100 mg to 45.5% at 300 mg. Without carbidopa tolerance is better, but the logic remains the same: the faster the dose increases, the more the stomach protests.
Why does 5-HTP cause nausea?
Because some of the 5-HTP is converted to serotonin in the intestine before reaching the brain, and intestinal serotonin stimulates receptors involved in nausea and vomiting. About 90% of the body's serotonin is digestive. This is also why researchers sometimes combine 5-HTP with carbidopa, which blocks this peripheral conversion, a medication reserved for supervised use.
How to avoid nausea with griffonia?
Three steps: start with a single capsule and only increase every 5 to 7 days; take the capsule during a meal rather than on an empty stomach; and spread the dose in two doses rather than one. If nausea persists after a week at the lowest dose, it is reasonable to stop.
Can you drive or drink alcohol with griffonia?
Drowsiness is among the reported effects, especially at the beginning of treatment and in the evening: assess your reaction before driving at night after taking it. As for alcohol, no specific interaction is documented, but alcohol impairs sleep and mood, that is exactly what you are trying to improve.
The interactions
What is serotonin syndrome?
A reaction linked to excessive stimulation of serotonin receptors, ranging from simple side effects to a severe presentation. It combines neuromuscular excitation (tremors, contractions, brisk reflexes), signs of autonomic nervous system dysfunction (fever, sweating, rapid heart rate, diarrhea), and altered mental status (agitation, confusion). It occurs in a person who has recently started or increased a serotonergic treatment, or combined two of them.
Which medications should not be combined with griffonia?
All serotonergic agents: SSRIs and SNRIs antidepressants, tricyclics, MAOIs, tramadol, migraine triptans, lithium, linezolid (an antibiotic), dextromethorphan in cough syrups, St. John's Wort, and Parkinson's disease treatments with levodopa or carbidopa. A case of serotonin syndrome from combining 5-HTP and linezolid has been published.
Can griffonia be taken at the same time as an antidepressant?
Not on your own initiative. A trial showed that fluoxetine significantly amplifies the hormonal response to 5-HTP, confirming that both act on the same pathway. Psychiatrists have used 5-HTP as an add-on to an antidepressant under monitoring, with encouraging results in pilot trials, but this is a prescriber's decision, made with follow-up.
What symptoms should prompt immediate discontinuation?
Unusual agitation or confusion, tremors or involuntary muscle contractions, profuse sweating, fever, racing heart, sudden diarrhea, especially in the hours or days following a dose or the addition of another medication: stop and seek medical advice without delay. These are the described signs of serotonin syndrome, whose early recognition is the main factor for good prognosis.
Special situations
Can griffonia be taken during pregnancy or while breastfeeding?
No. There is no safety trial in pregnant women, and a cohort of 1,115 pregnancies associated elevated maternal 5-HTP concentrations in the first trimester with reduced embryonic and fetal growth as well as increased risk of low birth weight for gestational age. These data concern 5-HTP produced by the body, not supplementation, but they are sufficient to justify caution. There is also no data during breastfeeding.
Is griffonia dangerous for the liver or kidneys?
No signal of hepatic or renal toxicity has been reported at usual doses. A study in 120 rats receiving 5-HTP in their drinking water for one year, including at high doses, found no hematological, hepatic, or renal abnormalities nor signs of eosinophilia-myalgia, with the only difference being lower blood pressure.
Should breaks be taken during a griffonia course?
Clinical trials last 4 to 12 weeks and there are no long-term human trials. Courses of 2 to 3 months followed by a break remain the best-documented framework; beyond that, medical advice is reasonable, if only to verify that the problem being treated is indeed the one you believe it to be.
Historical cases
What is the Peak X and eosinophilia-myalgia affair?
In 1989, an epidemic of eosinophilia-myalgia syndrome, a disease combining muscle pain and elevated levels of a type of white blood cell, was attributed to tryptophan contaminated by a single manufacturer. In 1994, a case of a related syndrome was described in a family exposed to 5-HTP containing an impurity absent from other batches. Analyses subsequently identified in several commercial 5-HTP products a family of contaminants called Peak X. It is therefore not the molecule itself that is at issue but the purity of the batches, making extract quality a safety criterion.
Can 5-HTP cause a skin disease?
A case of disease resembling scleroderma was published in 1980 in a patient treated with high doses of L-5-HTP combined with carbidopa for myoclonus, with elevated kynurenine levels. This is a particular medical context, doses far exceeding those of a supplement, and a drug combination. No comparable signal has been reported with griffonia extract at usual doses.
What happens in case of overdose?
A case published in 2022 describes a 44-year-old man who ingested ten times the recommended dose of 5-HTP powder: he developed marked amnesia and disorientation within four hours, with imaging showing reversible involvement of both hippocampi, with no loss of consciousness or seizure. His memory recovered sufficiently to return to work in two months and imaging was normal at eleven months. This is a reminder that the safety margin of a supplement is not infinite.
Glossary
- 5-HTP
- 5-hydroxytryptophan, direct precursor of serotonin, extracted from griffonia seeds.
- Serotonin syndrome
- Excessive stimulation of serotonin receptors, combining neuromuscular excitation, autonomic dysfunction, and altered mental status.
- Serotonergic
- Referring to a substance that increases serotonin activity, regardless of its class.
- Carbidopa
- Medication that blocks the conversion of 5-HTP to serotonin outside the brain; multiplies 5-HTP exposure by fifteen.
- Eosinophilia
- Increase in a type of white blood cell, a marker of eosinophilia-myalgia syndrome.
- Peak X
- Name given to a family of contaminants identified in certain batches of commercial 5-HTP in the late 1990s.
- Kynurenine
- Metabolite of tryptophan following a pathway parallel to that of serotonin; its levels were elevated in the 1980 scleroderma case.
- Standardization
- Guarantee of a fixed percentage of active ingredient in an extract, here 30% 5-HTP.
Sources
The studies cited below were identified via PubMed.
- Mikkelsen N, Damkier P, Pedersen SA. Serotonin syndrome: a targeted review. Basic and Clinical Pharmacology and Toxicology, 2023;133(2):124-129. DOI
- Smarius LJCA, Jacobs GE, Hoeberechts-Lefrandt DHM, et al. Pharmacology of increasing oral doses of 5-HTP with carbidopa. Journal of Psychopharmacology, 2008;22(4):426-433. DOI
- Gijsman HJ, van Gerven JMA, de Kam ML, et al. Comparison versus placebo of three dosing schedules of 5-HTP in healthy volunteers. Journal of Clinical Psychopharmacology, 2002;22(2):183-189. DOI
- Ostabal Artigas MI. Serotonin syndrome from interaction between linezolid and 5-hydroxytryptophan. Medicina Clínica, 2015;145(12):e37-e38. DOI
- Meltzer H, Bastani B, Jayathilake K, Maes M. Fluoxetine, but not tricyclics, potentiates cortisol and prolactin elevation induced by 5-HTP. Neuropsychopharmacology, 1997;17(1):1-11. DOI
- van Zundert SKM, van Egmond NCM, van Rossem L, et al. Maternal tryptophan metabolism in the first trimester and embryonic and fetal growth. Human Reproduction, 2024;39(5):912-922. DOI
- Michelson D, Page SW, Casey R, et al. A disorder related to eosinophilia-myalgia syndrome associated with exposure to L-5-HTP. The Journal of Rheumatology, 1994;21(12):2261-2265. PubMed
- Klarskov K, Johnson KL, Benson LM, et al. Structural characterization of the peak X contaminant in commercial 5-HTP preparations. The Journal of Rheumatology, 2003;30(1):89-95. PubMed
- Sternberg EM, Van Woert MH, Young SN, et al. Development of scleroderma-like disease during treatment with L-5-HTP and carbidopa. New England Journal of Medicine, 1980;303(14):782-787. DOI
- Nash E, Jamshidi N. Hippocampal ischemia following accidental 5-HTP overdose: a clinical case. Clinical Neurology and Neurosurgery, 2022;220:107384. DOI
- Gwaltney-Brant SM, Albretsen JC, Khan SA. 5-HTP toxicity in dogs: 21 cases. Journal of the American Veterinary Medical Association, 2000;216(12):1937-1940. DOI
- Preuss HG, Echard B, Talpur N, Funk KA, Bagchi D. Does 5-HTP cause acute and chronic toxic disturbances in rats? Toxicology Mechanisms and Methods, 2006;16(5):281-286. DOI
