Medication Search​ - phl-Tryptophan

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How does phl-Tryptophan work? What will it do for me?

L-tryptophan is used in addition to antidepressants to treat bipolar affective disorder. It works by affecting the levels of certain chemicals in the brain called neurotransmitters.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does phl-Tryptophan come in?


Each white, opaque, size 00 Coni-snap capsule printed "P" logo and "T 500" in black ink on both body and cap, contains 500 mg of L-tryptophan. Nonmedicinal ingredients: carboxymethylcellulose sodium, croscarmellose
sodium, magnesium stearate, gelatin, and titanium dioxide.


500 mg
Each white to off-white, oblong, clear film-coated tablet, imprinted with "P" logo on one side and "T5" on the other side, contains 500 mg of L-tryptophan, USP. Nonmedicinal ingredients: carboxymethylcellulose sodium,
croscarmellose sodium, hydroxypropyl methylcellulose, magnesium stearate, and polyethylene glycol.

1 g
Each white, oblong, clear film-coated tablet, imprinted with "P" logo on one side and "T1" on the other side, contains 1 g of L-tryptophan, USP. Nonmedicinal ingredients: carboxymethylcellulose sodium, croscarmellose sodium,
hydroxypropyl methylcellulose, magnesium stearate, and polyethylene glycol.

How should I use phl-Tryptophan?

The usual recommended adult dose of L-tryptophan is 8 g to 12 g daily taken in 3 to 4 equally divided doses with meals or snacks. For best results, take L-tryptophan with a low-protein, carbohydrate-rich snack or meal.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are
taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take phl-Tryptophan?

Do not take this medication if you are allergic to L-tryptophan or any ingredients of the medication.

What side effects are possible with phl-Tryptophan?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • dizziness
  • drowsiness
  • dry mouth
  • headache
  • loss of appetite
  • nausea

Although most of the side effects listed below don’t happen very often, they could lead to serious problems if you do not seek medical attention.

Seek immediate medical attention if any of the following symptoms of overdose occur:

  • agitation
  • confusion
  • diarrhea
  • fever
  • overactive reflexes
  • poor coordination
  • restlessness
  • shivering
  • sweating
  • talking or acting with excitement you cannot control
  • trembling or shaking
  • twitching
  • vomiting

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for phl-Tryptophan?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Diabetes: If you have diabetes, your doctor should closely monitor your condition while you are taking L-tryptophan, as it may affect blood sugar control.

Drowsiness: This medication can cause drowsiness, affecting your ability to drive or operate machinery. Avoid these and other hazardous tasks until you know how tryptophan affects you.

Other medical conditions: If you have low stomach acid, other stomach or intestine problems, or a history of cataracts, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing
and effectiveness of this medication, and whether any special monitoring is needed.

Vitamin B6 supplements: Your doctor may recommend that you take vitamin B6 supplements to reduce your risk of bladder cancer.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if L-tryptophan passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

What other drugs could interact with phl-Tryptophan?

There may be an interaction between L-tryptophan and any of the following:

  • lithium
  • monoamine oxidase inhibitors (e.g., moclobemide, phenelzine, tranylcypromine)
  • selective norepinephrine reuptake inhibitors (SNRIs; e.g., venlafaxine)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., fluoxetine, fluvoxamine, paroxetine, sertraline)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you
take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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