• Basic Info
• Top Questions
• Interactions

L-tryptophan may interact with other medicines. Before taking L-tryptophan, tell your doctor or care practitioner if you are also using:

• medicine for depression such as St. John's wort, citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), paroxetine (Paxil), sertraline (Zoloft), amitriptyline (Elavil), imipramine (Tofranil), venlafaxine (Effexor), and others;

• a monoamine oxidase inhibitor (MAOI) such as tranylcypromine (Nardil), phenelzine (Parnate), selegiline (Eldepryl), or isocarboxazid (Marplan);

• a sedative or tranquilizer such as diazepam (Valium), lorazepam (Ativan), clonazepam (Klonipin) and others;

• a phenothiazine drug such as chlorpromazine, (Thorazine), prochlorperazine (Compazine) and others; or

• drugs that make you sleepy (such as alcohol, cold medicine, pain medication, muscle relaxants, and medicine for depression or anxiety).

If you are using any of these drugs, you may not be able to take L-tryptophan, or you may need dosage adjustments or special tests during treatment.

There may be other drugs not listed that can affect L-tryptophan. Tell your doctor or care practitioner about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor or care practitioner.

Stop using L-tryptophan and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

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.

There have been no published cases of EMS within the last several years, but you should be aware of the symptoms. Call your doctor at once if you have any of the following:

• 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);

• breathing difficulty; or

• uneven heartbeat.

Other less serious side effects are more likely to occur. Talk with your doctor or care practitioner if you have any of these less serious side effects:

• dry mouth, heartburn, burping, gas;

• nausea, vomiting, diarrhea;

• feeling drowsy or light-headed;

• blurred vision;

• weakness, lack of coordination;

• headache; or

• lost appetite.

Side effects other than those listed here may also occur. Talk to your doctor or care practitioner about any side effect that seems unusual or that is especially bothersome.