Possible Interaction: Fluoxetine and Tryptophan

“The interactions between fluoxetine and lithium, tryptophan and monoamine oxidase inhibitors, in particular, are potentially serious, and can lead to the ‘serotonergic syndrome’.”

“Steiner W, Fontaine R. Toxic reaction following the combined administration of fluoxetine and L-tryptophan : five case reports.”

“Steiner W, Fontaine R. Toxic reaction following the combined administration of fluoxetine and L-tryptophan : five case reports.”

“However, we report the occurrence of a toxic reaction in all five cases following combined administration of fluoxetine and L-tryptophan.”

“Identification of plasma metabolic profiles indicated that significant changes in specific metabolites occurred after fluoxetine exposure, including increased phenylalanine, serine, acetyl-L-carnitine, carnitine and decreased creatine, betaine, proline, tryptophan , tyrosine, C16:0 LPC.”

“ Tryptophan modulated effects of several drugs on neuronal firing rates, including a selective 5-HT(1A) receptor antagonist (WAY-100635), a monoamine oxidase inhibitor (pargyline), a selective serotonin reuptake inhibitor ( fluoxetine ), and a serotonin-releasing agent (methylenedioxymethamphetamine).”

“Administration of fluoxetine-HCl (20 mg/kg) inhibited holo and total Tp pyrrolase enzyme activities when compared to saline injected rats and ultimately increases liver Tp concentrations.”

“When combined with tryptophan, fluoxetine augmented and DMI diminished the effects of tryptophan on all behaviors.”

“ Tryptophan (TRP) levels in the three brain areas were significantly increased with clomipramine and fluoxetine but not with moclobemide.”

“Thus, concomitant L-tryptophan plus fluoxetine treatment decreased the intensity of aggressive postures and increased the time of latency before first attack.”