Drug & supplement interaction

L-tryptophan + Valproic Acid

Valproic Acid brand names: Depakene, Depacon, Valproate.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Valproic Acid falls into 2 drug categories that L-tryptophan can interact with; the most serious is rated major. Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

L-tryptophan and Valproic Acid

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

L-tryptophan interacts with whole categories of medication. Valproic Acid falls into 2 of those categories, so it can interact with L-tryptophan in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

CNS DEPRESSANTS

1 of 2

Why this applies to Valproic Acid

Valproic Acid falls under CNS DEPRESSANTS — the group L-tryptophan interacts with.

Theoretically, concomitant use of L-tryptophan with CNS depressants might cause additive sedative effects.
Clinical research shows that L-tryptophan can cause fatigue and drowsiness.
Severity Major Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: both L-tryptophan and valproic acid can make you feel sleepy or mentally foggy on their own. Put them together and those drowsy effects can stack up. This isn't about tryptophan changing how your body breaks down the medication. It's more that you may end up with extra sedation, slower thinking, more tiredness, or feeling unsteady on your feet.

The concern is mostly theoretical and graded as moderate evidence, but it's worth taking seriously, especially since valproic acid can already cause drowsiness and dizziness. If you're tempted to try tryptophan for sleep or mood, please check with your pharmacist or doctor first rather than starting it on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lieberman HR, Corkin S, Spring BJ. The effects of dietary neurotransmitter precursors on human behavior. Am J Clin Nutr 1985;42:366-70. PubMed
Moderate

SEROTONERGIC DRUGS

2 of 2

Valproic Acid also falls under SEROTONERGIC DRUGS.

Theoretically, combining L-tryptophan with serotonergic drugs might cause additive serotonergic effects.
L-tryptophan is a precursor to serotonin. Theoretically, combining serotonergic drugs with L-tryptophan might increase the risk of serotonergic side effects, including serotonin syndrome and cerebral vasoconstrictive disorders.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture with L-tryptophan and valproic acid. This pairing is flagged because your body turns tryptophan into serotonin, and the concern is that stacking it with a drug that nudges serotonin signaling could add up. I want to be straight with you though: valproic acid isn't a classic serotonergic medication the way an SSRI antidepressant is, so this interaction is theoretical and based on general pharmacology, not strong real-world reports.

In practice, the realistic worry would be extra serotonin-type symptoms like restlessness, shivering, sweating, fast heartbeat, or confusion. That's uncommon here, but worth knowing. Since valproic acid is a seizure and mood medication you don't want to disturb, please check with your pharmacist or doctor before adding tryptophan rather than starting it on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Messiha FS. Fluoxetine: adverse effects and drug-drug interactions. J Toxicol Clin Toxicol 1993;31:603-30. PubMed
  2. Singhal AB, Caviness VS, Begleiter AF, et al. Cerebral vasoconstriction and stroke after use of serotonergic drugs. Neurology 2002;58:130-3. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

L-tryptophan Also Interacts With Other Medications

L-tryptophan has 247 major, 146 moderate known drug interactions in our database — the Valproic Acid one above is among them. If you take anything else, check it against the full list below.

Major 247 Moderate 146 No known interaction 2,437 (incl. Valproic Acid)
Taking anything else?

Check Another of Your Medications Against L-tryptophan

Covers the 2,830 medications we’ve checked against L-tryptophan. Pick one to open its full report.

From our Q&A

Questions About L-tryptophan or Valproic Acid

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers L-tryptophan or Valproic Acid, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Valproic Acid

This page covers L-tryptophan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Valproic Acid page lists 173 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 147 moderate · 17 minor.

From our pharmacist’s overview on the Valproic Acid page

“Anyone taking valproic acid (Depakene, Depacon) for seizures or bipolar disorder should treat this list with genuine care. Of the 173 supplements and herbs on file, nine are rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Valproic Acid interaction page

One more smart check

Taking L-tryptophan as Part of a Dietary Supplement Product? Check It for Interactions

We hold 5 real supplement products containing L-tryptophan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides L-tryptophan. Your product may carry other ingredients that interact with Valproic Acid too, on top of L-tryptophan — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where L-tryptophan and Valproic Acid Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement L-tryptophan
Steady interest

#1,025 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Valproic Acid
Top 25%

#390 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About L-tryptophan

What is L-tryptophan?

L-tryptophan
  • Sleep problems
  • Low mood and depression
  • Anxiety
  • Premenstrual symptoms
  • Appetite and food cravings

L-tryptophan is an essential amino acid the body uses to make serotonin and melatonin, and people take it to support sleep and mood. The evidence for supplement use is limited and mixed, and there are real safety concerns, so talk to a pharmacist or doctor before trying it.

Read the full L-tryptophan monograph & all interactions
Medication

About Valproic Acid

What Is Valproic Acid Used For?

Brand names: Depakene, Depacon, Valproate

Valproic acid capsules (brands Valproic and Valproic Acid) and valproic acid oral solution (brand Valproic Acid) are both used to treat epilepsy. Specifically, they are approved for complex partial seizures (either alone or with other seizure types) as monotherapy or add-on therapy, and for simple and complex absence seizures as sole therapy or add-on therapy.

Both forms are intended for adults and pediatric patients. Always follow your prescriber's guidance on which product and regimen is right for you.

See full Valproic Acid drug information
Keep checking

Other Drugs & L-tryptophan

Browse every other medication we’ve checked against L-tryptophan — both the ones with a known interaction and the ones without. Select any drug for the full detail.

247Major
146Moderate
0Minor
2,436No known interaction
247 Major 146 Moderate 2,436 No interaction
Major

247 interactions

Showing 60 of 247 major interactions — see all 247 on the L-tryptophan page.

Moderate

146 interactions

Showing 60 of 146 moderate interactions — see all 146 on the L-tryptophan page.

No interaction 2,436 drugs checked — show the list

We also checked L-tryptophan against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,436 medications checked with no known interaction — see the full L-tryptophan list.

See the full L-tryptophan interactions page
See every supplement checked against Valproic Acid, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
L-tryptophan monograph › Uses, safety, and every drug interaction in one place Valproic Acid supplement interactions › Every supplement checked against Valproic Acid, ranked by severity Valproic Acid drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking L-tryptophan and Valproic Acid Together: Common Questions

Can you take L-tryptophan with Valproic Acid?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for L-tryptophan and Valproic Acid?
Valproic Acid belongs to more than one drug category, and L-tryptophan interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the L-tryptophan and Valproic Acid interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Valproic Acid and L-tryptophan?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.