Hydroxytryptophan and Linezolid Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Hydroxytryptophan
No brand names on recordLinezolid Injection
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
An increased risk of serotonin syndrome (hypertension, hyperthermia, myoclonus, mental status changes)
Interaction Deep Dive
The concomitant use of serotonin precursors, such as hydroxytryptophan or tryptophan with MAOI is contraindicated due to the potential of life-threatening serotonin syndrome. At least 14 days should elapse between the discontinuation of a MAOI and initiation of a serotonergic drug1.
Why it happens (mechanism)
Additive serotonergic effect
Literature reports
5 reports — tap to read
a) Eight cases of delirious syndromes associated with the addition of tryptophan to MAOI therapy were reported. All patients were on tranylcypromine 40 mg to 130 mg daily and tryptophan 1 g to 6 g daily with the time to onset of delirium ranging from two days to four weeks after started tryptophan therapy. Principle symptoms included confusion, disorientation, myoclonic jerks, agitation, and delirium. Resolution of the delirious state was 12 hours to four days after the discontinuation of both the MAOI and tryptophan 2.
b) A 42-year old woman taking phenelzine and tryptophan experienced delirium 3. The patient was taking phenelzine 45 mg daily for four weeks when she began taking tryptophan 2040 mg for sleep disturbances. Several hours later, the patient developed a headache and began to engage in bizarre and inappropriate behavior. Upon presentation to the emergency department, the patient was loud, agitated, disoriented, and paranoid. Lorazepam 2 mg was administered intramuscularly. After discontinuation of both medications, the patient's symptoms resolved over the next eight hours. Therapy with phenelzine was later restarted without incident.
c) Three patients developed symptoms of hyperreflexia, jaw quivering, teeth chattering, and diaphoresis shortly after adding tryptophan 2 g daily to the existing therapy of phenelzine 60 mg daily 4.
d) A 42-year-old woman experienced a sudden onset of restlessness, sweating, and confusion. Medication therapy included lithium 800 mg daily, L-tryptophan 1 g daily, diazepam 6 mg daily, and triazolam 0.25 mg daily. Six weeks prior to the onset of symptoms, phenelzine 15 mg three times daily had been started. On admission, her lithium level was 0.38 mmol/L (therapeutic range 0.5 to 1.0 mmol/L). Within three hours of the onset of symptoms, the woman was comatose and a diagnosis of neuroleptic malignant syndrome was made. She was treated with intravenous dantrolene 60 mg three times daily with no success. Acute renal failure and severe disseminated intravascular coagulation followed, and the patient died on the sixth day of hospitalization 5.
e) A fatal malignant hyperpyrexia syndrome occurred in a 48-year-old female being treated with chlorpromazine 600 mg daily, lithium 800 mg daily, L-tryptophan 6 g daily, and phenelzine 45 mg daily. Symptoms of incoherent speech, reduced consciousness, muscular rigidity, nystagmus, and hyperreflexia occurred within a few weeks of the initiation of phenelzine therapy. She was diagnosed with neuroleptic malignant syndrome and treated with procyclidine. Respiratory and cardiac arrest soon followed, and the patient died. The timing of her death points to the effect of combined phenelzine, lithium, and L-tryptophan, since lithium and L-tryptophan had been coadministered for the previous four months before phenelzine was started 6.
Common questions
Can I take Hydroxytryptophan and Linezolid Injection together?
An increased risk of serotonin syndrome (hypertension, hyperthermia, myoclonus, mental status changes) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Hydroxytryptophan and Linezolid Injection interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Hydroxytryptophan or Linezolid Injection need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (6)
- Product Information: phenelzine sulfate oral film coated tablets, phenelzine sulfate oral film coated tablets. Greenstone, LLC (per DailyMed), Peapack, NJ, 2011. DailyMed
- Pope HG, Jonas JM, & Hudson JI: Toxic reactions to the combination of monoamine oxidase inhibitors and tryptophan. Am J Psychiatry 1985; 142:491-492. PubMed
- Alvine G, Black DW, & Tsuang D: Case of delirium secondary to phenelzine/L-tryptophan combination (letter). J Clin Psychiatry 1990; 51:311.
- Levy AB, Bucher P, & Votolato N: Myoclonus, hyperreflexia and diaphoresis in patients on phenelzine-tryptophan combination treatment. Can J Psychiatry 1985; 30:434-436. PubMed
- Brennan D, MacManus M, Howe J, et al: Neuroleptic malignant syndrome without neuroleptics (letter). Br J Psychiatry 1988; 152:578-579. DOI
- Staufenberg EF & Tantam D: Malignant hyperpyrexia syndrome in combined treatment (letter). Br J Psychiatry 1989; 154:577-578. PubMed
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