Pronunciation: L TRIP toe fan

What is the most important information I should know about L-tryptophan?

Follow all directions on the product label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

What is L-tryptophan?

L-tryptophan is an amino acid that is made from plant or animal sources. L-tryptophan is known as an "essential" amino acid because the body does not produce it. L-tryptophan is important to the functions of many organs in the body. When you consume L-tryptophan, your body absorbs it and changes it to eventually become a hormone called serotonin. Serotonin transmits signals between your nerve cells and also narrows (constricts) blood vessels. The amount of serotonin in the brain can affect mood.

L-tryptophan has been used in alternative medicine as a possibly effective aid in treating symptoms of premenstrual dysphoric disorder syndrome (such as mood swings and irritability), and to help people quit smoking.

L-tryptophan has also been used to treat facial pain, to relieve bruxism (tooth grinding), and to improve athletic performance. However, research has shown that L-tryptophan may not be effective in treating these conditions.

Other uses not proven with research include treating sleep problems (insomnia), anxiety, depression, and attention deficit hyperactivty disorder (ADHD).

It is not certain whether L-tryptophan is effective in treating any medical condition. Medicinal use of this product has not been approved by the FDA. L-tryptophan should not be used in place of medication prescribed for you by your doctor.

L-tryptophan is often sold as an herbal supplement. There are no regulated manufacturing standards in place for many herbal compounds and some marketed supplements have been found to be contaminated with toxic metals or other drugs. Herbal/health supplements should be purchased from a reliable source to minimize the risk of contamination.

It may be dangerous to purchase L-tryptophan on the Internet or from vendors outside of the United States. The manufacture, sale, and distribution of L-tryptophan outside of the U.S. does not comply with the regulations of the Food and Drug Administration (FDA) for the safe use of this medication.

L-tryptophan may also be used for purposes not listed in this product guide.

What should I discuss with my health care provider before taking L-tryptophan?

You should not use this product if you are allergic to tryptophan.

Ask a doctor, pharmacist, or other healthcare provider if it is safe for you to use this product if you have:

  • liver disease;
  • kidney disease;
  • eosinophilia (high levels of a certain type of white blood cells); or
  • a muscle disorder (such as fibromyalgia).

L-tryptophan is considered likely unsafe to use during pregnancy. Do not use this product without medical advice if you are pregnant.

It is not known whether L-tryptophan passes into breast milk or if it could harm a nursing baby. Do not use this product without medical advice if you are breast-feeding a baby.

Do not give any herbal/health supplement to a child without medical advice.

How should I take L-tryptophan?

When considering the use of herbal supplements, seek the advice of your doctor. You may also consider consulting a practitioner who is trained in the use of herbal/health supplements.

If you choose to use L-tryptophan, use it as directed on the package or as directed by your doctor, pharmacist, or other healthcare provider. Do not use more of this product than is recommended on the label.

Call your doctor if the condition you are treating with L-tryptophan does not improve, or if it gets worse while using this product.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra L-tryptophan to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking L-tryptophan?

Avoid taking an herbal supplement containing St. John's wort at the same time you are taking L-tryptophan.

Avoid using L-tryptophan together with other herbal/health supplements that can also cause drowsiness, including 5-hydroxytryptophan (5-HTP), calamus, California poppy, catnip, hops, Jamaican dogwood, kava, St. John's wort, skullcap, valerian, or yerba mansa.

Avoid using L-tryptophan together with other herbal/health supplements that can raise your serotonin levels. This includes 5-HTP, Hawaiian baby woodrose, and S-adenosylmethionine (SAMe).

L-tryptophan may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

What are the possible side effects of L-tryptophan?

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Although not all side effects are known, L-tryptophan is thought to be possibly unsafe. Be sure to use this product only if you have obtained it from a safe and reputable source.

In 1989, a life-threatening condition called eosinophilia-myalgia syndrome (EMS) occurred in many people using L-tryptophan and some died from the condition. All of these people had taken L-tryptophan distributed by a company in Japan. This L-tryptophan was found to contain trace levels of impure ingredients. Since that time, the FDA has limited the availability of L-tryptophan in the U.S. However, the increased use of the Internet has made many dietary supplements available from non-U.S. sources.

Although there have been no published cases of EMS within the last several years, you should be aware of the symptoms. Stop using L-tryptophan and seek emergency medical help if you have signs of EMS:

  • unusual tiredness;
  • severe muscle pain (most often in the shoulders, back, or legs);
  • weakness, numbness, tingling, or burning pain (especially at night);
  • tremors or twitching muscle movements;
  • swelling in any part of your body;
  • skin changes (dryness, yellowing, hardening, rash, hair loss);
  • breathing difficulty; or
  • uneven heartbeat.

Common side effects may include:

  • feeling drowsy or light-headed;
  • dry mouth, heartburn, burping, gas;
  • stomach pain, nausea, vomiting, diarrhea;
  • weakness, lack of coordination;
  • blurred vision;
  • headache; or
  • sexual problems.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect L-tryptophan?

Taking L-tryptophan with other drugs that make you sleepy can worsen this effect. Ask your doctor before taking L-tryptophan with a sleeping pill, narcotic pain medicine, muscle relaxer, or medicine for anxiety, depression, or seizures.

Do not take L-tryptophan without medical advice if you are using any of the following medications:

  • tramadol (Ultram, Ultracet);
  • a cough medicine that contains dextromethorphan (Delsym, Robitussin DM, and others);
  • an MAO inhibitor such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others;
  • medicine to treat mental illness such as chlorpromazine (Thorazine), fluphenazine (Prolixin), thioridazine (Mellaril), and others;
  • a narcotic medicine such as meperidine (Demerol) or pentazocine (Talwin); or
  • a sedative such as diazepam (Valium), clonazepam (Klonopin), lorazepam (Ativan), and others.

This list is not complete. Other drugs may interact with L-tryptophan, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this product guide.

Where can I get more information?

Consult with a licensed healthcare professional before using any herbal/health supplement. Whether you are treated by a medical doctor or a practitioner trained in the use of natural medicines/supplements, make sure all your healthcare providers know about all of your medical conditions and treatments.

This information does not replace the advice of a doctor. Healthwise, Incorporated, disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Learn how we develop our content.