The short answer
5-HTP may add to chlorzoxazone-related drowsiness or impaired alertness. Review the exact product and other sedating medicines before adding it; this combination’s risk has not been measured directly.
What this answer covers
Oral L-5-hydroxytryptophan, not every mixed sleep product.
- Supplement or preparation
- L-5-HTP
- Medication ingredient
- chlorzoxazone
The medicine can affect alertness
Drowsiness and dizziness; additive CNS-depressant effects. Rare serious hepatotoxicity warning is intrinsic and not proof of supplement synergy. These medication warnings do not supply a supplement-specific adverse-event rate.
What the supplement evidence shows
A small older-adult trial found improvement in some sleep measures with 5-HTP. It did not test this medicine or measure combined daytime impairment. Health Canada’s monograph separately cautions about drowsiness; sleep benefit is not itself proof of added toxicity.
Keep the preparation and outcome clear
Dose, formulation and other ingredients matter. No exact-pair trial identified here established how much impairment would increase, and a negative result for one product alone does not prove the combination safe.
Review co-use and daily activities
Discuss the product with the prescriber or pharmacist before adding it. Avoid driving while drowsy or dizzy. No exact protective spacing interval was established, and a supplement should not be used to counteract medication impairment.
Evidence and practical considerations
Side effects & toxicity
Conditional additive-alertness precaution from medication-specific effects and supplement guidance; direct pair harm, respiratory depression rate and protective spacing not established.
- Exact scope
- Oral L-5-hydroxytryptophan, not every mixed sleep product. with Oral chlorzoxazone tablets.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair incidence, blanket class transfer or arbitrary spacing interval.
Factors that may matter: Preparation; Dose; Other medicines; Organ function.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed chlorzoxazone
Drowsiness and dizziness; additive CNS-depressant effects. Rare serious hepatotoxicity warning is intrinsic and not proof of supplement synergy.
How this applies: Exact chlorzoxazone RxCUI 2410 IN, with stated salt/formulation/route bridge.
No exact supplement-combination incidence or validated protective spacing; salt, route and release form limits apply.
Source 2: Regulatory supplement monograph
webprod.hc-sc.gc.ca · Source check Sep 10, 2026
Population: People considering the covered oral L-5-HTP preparations.
Warns about drowsiness and driving; antidepressant restrictions are stated separately.
How this applies: Interpreted for chlorzoxazone only within the stated exact preparation and endpoint limits.
No exact chlorzoxazone combination trial; original population, preparation and endpoint restrictions apply. No quantified pair risk or protective dose interval.
Source 3: Original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Thirty older adults in a single-blind study.
Some sleep measures improved, particularly among poor sleepers.
How this applies: Interpreted for chlorzoxazone only within the stated exact preparation and endpoint limits.
No exact chlorzoxazone combination trial; original population, preparation and endpoint restrictions apply. No quantified pair risk or protective dose interval.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Article prepared | |
| Prepared exact chlorzoxazone article with formulation-specific evidence and uncertainty. |
Article revision: aba697e6aa3d97f7
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.