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Complementary/Alternative Medicine: This monograph describes a natural or herbal product that is not subject to FDA guidelines for medicines. Patients and clinicians are advised to read package labels carefully to ensure safe and efficacious use.


Trade Name(s)

  • tryptophan

Ther. Class.
mood stabilizers
smoking deterrents

Common Uses

  • Premenstrual dysphoric disorder (PMDD)
  • Depression.
  • Smoking cessation.
  • Insomnia.


L-tryptophan is an essential amino acid that is converted by the body to 5–hydroxytryptophan (5–HTP) and then to serotonin. Both L-tryptophan and 5–HTP cross the blood-brain barrier and have sedative effects. Depletion of endogenous tryptophan can cause a relapse in depression symptoms.

Therapeutic Effect(s):

  • Improved symptoms of depression.
  • Improved sleep.


Absorption: Unknown

Distribution: Unknown

Metabolism and Excretion: Unknown

Half-life: Unknown




Contraindicated in:

  • Hypersensitivity.
  • Pregnancy and lactation.

Use Cautiously in:

  • Eosinophilia.
  • Kidney disease.
  • Liver disease.

Adverse Reactions/Side Effects

CNS: ataxia, headache, drowsiness, lightheadedness

EENT: visual blurring

GI: heartburn, abdominal pain, dry mouth, nausea

Hemat: eosinophilia-myalgia syndrome

* CAPITALS indicate life-threatening.
Underline indicate most frequent.


Natural Drug Interaction

  • Increased risk of serotonergic effects and serotonin syndrome with SSRIs, dextromethorphan, meperidine, tricyclic antidepressants monoamine oxidase inhibitors pentazocine and tramadol..
  • Increased sedation with CNS depressants..


  • Additive sedation with herbs or supplements that have sedative properties such as kava St. John's wort valerian 5–HTP and others.
  • Increased risk of serotonin syndrome with St. John's wort. .


PO: (Adults) Insomnia– 1 gram 20 minutes before bedtime; Depression– 300 mg/day; Prementrual syndrome– 6 grams/day; Smoking cessation– 50 mg/kg/day.


Tablets: 500 mg


  • Assess sleep patterns prior to and periodically during therapy.
  • Monitor for signs and symptoms of esosinophilia-myalgia sydrome (severe myalgia, arthralgia, intense eosinophilia) Less common symptoms include respiratory prodrome (cough, dyspnea, pulmonary infiltrates), limb edema, scleroderma, mononeuritis, evanescent skin rash, mild LFT elevations, and leukocytosis. If these symptoms occur, discontinue l-tryptophan.

Potential Diagnoses


  • PO: Administer without regard to food.

Patient/Family Teaching

  • Instruct patient to take as directed; do not take more than directed.
  • Advise patient to notify health care professional of symptoms of esosinophilia-myalgia sydrome occur.
  • Advise female patient to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

Evaluation/Desired Outcomes

Improvement in insomnia and premenstrual disorder.

L-tryptophan is a sample topic from the Davis's Drug Guide.

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Quiring, Courtney, et al. "L-tryptophan." Davis's Drug Guide, 16th ed., F.A. Davis Company, 2019. Nursing Central, nursing.unboundmedicine.com/nursingcentral/view/Davis-Drug-Guide/110127/all/L_tryptophan.
Quiring C, Sanoski CA, Vallerand AH. L-tryptophan. Davis's Drug Guide. 16th ed. F.A. Davis Company; 2019. https://nursing.unboundmedicine.com/nursingcentral/view/Davis-Drug-Guide/110127/all/L_tryptophan. Accessed April 22, 2019.
Quiring, C., Sanoski, C. A., & Vallerand, A. H. (2019). L-tryptophan. In Davis's Drug Guide. Available from https://nursing.unboundmedicine.com/nursingcentral/view/Davis-Drug-Guide/110127/all/L_tryptophan
Quiring C, Sanoski CA, Vallerand AH. L-tryptophan [Internet]. In: Davis's Drug Guide. F.A. Davis Company; 2019. [cited 2019 April 22]. Available from: https://nursing.unboundmedicine.com/nursingcentral/view/Davis-Drug-Guide/110127/all/L_tryptophan.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - L-tryptophan ID - 110127 A1 - Quiring,Courtney, AU - Sanoski,Cynthia A, AU - Vallerand,April Hazard, BT - Davis's Drug Guide UR - https://nursing.unboundmedicine.com/nursingcentral/view/Davis-Drug-Guide/110127/all/L_tryptophan PB - F.A. Davis Company ET - 16 DB - Nursing Central DP - Unbound Medicine ER -