SeriousContraindicated
Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI) that potently blocks serotonin reuptake. Adding 5-HTP, a direct serotonin precursor, significantly increases the risk of serotonin syndrome through excessive serotonin accumulation at synaptic receptors.
Recommendation: Do not combine 5-HTP with duloxetine. The risk of serotonin syndrome is significant with this combination. If you are taking 5-HTP, discontinue it and inform your prescriber before starting any SNRI.
DangerousContraindicated
Combining duloxetine (an SNRI) with St. John's Wort creates a serious risk of serotonin syndrome. Both agents increase synaptic serotonin through different mechanisms. St. John's Wort may also induce CYP1A2, which is the primary enzyme metabolizing duloxetine, creating complex and dangerous pharmacokinetic-pharmacodynamic interactions.
Recommendation: Do not take St. John's Wort with duloxetine under any circumstances. This combination poses dual risks: serotonin syndrome and unpredictable changes in duloxetine levels. Seek alternative mood support options.
SeriousCaution
SAMe has antidepressant and monoamine-modulating activity. Duloxetine increases serotonin and norepinephrine signaling, so adding SAMe may increase the risk of serotonin toxicity or mood activation. Watch for agitation, sweating, tremor, diarrhea, clonus, fever, insomnia, or manic symptoms.
Recommendation: Avoid starting SAMe with duloxetine unless the prescriber managing duloxetine approves and monitors the combination. Seek urgent care for clonus, high fever, severe agitation, confusion, or seizure.
DangerousContraindicated
Duloxetine blocks both serotonin and norepinephrine reuptake, and L-tryptophan provides extra substrate for serotonin synthesis. The combination can raise serotonin tone beyond the therapeutic range and precipitate serotonin syndrome. Risk rises if you also use tramadol, triptans, MDMA, St. John's Wort, or other antidepressants.
Recommendation: Do not take L-tryptophan supplements with duloxetine. Food tryptophan is fine; avoid concentrated sleep or mood products containing L-tryptophan. Get urgent help for clonus, high fever, severe restlessness, confusion, or muscle rigidity.
SeriousCaution
Duloxetine has a known rare risk of clinically significant liver injury, and substantial alcohol use is a recognized risk factor in labeling and postmarketing safety reviews. Combining duloxetine with heavy drinking can increase the chance that liver injury is severe or missed until jaundice, abdominal pain, dark urine, or marked fatigue appears. Alcohol may also worsen dizziness, sedation, and judgment while taking duloxetine.
Recommendation: Avoid heavy alcohol use while taking duloxetine. If you have alcohol use disorder, chronic liver disease, or abnormal liver tests, ask your prescriber about a different medication before starting duloxetine. Seek prompt medical care for jaundice, dark urine, severe right upper abdominal pain, or unexplained severe fatigue.
DangerousContraindicated
Duloxetine directly interferes with MDMA pharmacology at serotonin and norepinephrine transporters. In a controlled human study, duloxetine reduced MDMA's subjective and physiologic effects, which can encourage unsafe redosing, while MDMA exposure and serotonergic load remain clinically concerning. The combination can raise risk for serotonin syndrome, hyperthermia, hypertension, arrhythmia, and seizures.
Recommendation: Do not use MDMA while taking duloxetine. Do not increase MDMA doses to overcome duloxetine-related blunting. Seek emergency care for high fever, severe agitation, confusion, clonus, chest pain, fainting, or severe headache after exposure.
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