Tryptophan Interactions

Fluoxetine blocks serotonin reuptake while tryptophan supplies raw material for serotonin synthesis, and the combination can produce serotonin syndrome. Fluoxetine's very long half-life (active metabolite norfluoxetine persists for weeks) extends the window of risk well beyond the last dose.

Sertraline is a selective serotonin reuptake inhibitor (SSRI) that increases synaptic serotonin, and L-tryptophan is the dietary precursor to serotonin. Combining them can excessively elevate serotonergic activity, raising the risk of serotonin syndrome (agitation, tremor, hyperthermia, autonomic instability).

Tryptophan is converted in the liver to niacin (vitamin B3) at a ratio of roughly 60 mg tryptophan to 1 mg niacin, so adequate dietary tryptophan reduces the niacin requirement and helps maintain NAD/NADP coenzyme pools. Niacin in turn spares tryptophan for serotonin and melatonin synthesis, supporting mood and sleep.