Interactions with Tyrosine

L-tyrosine (200 and 400 mg/kg) significantly potentiated the anorexigenic effects of phenylpropanolamine (5, 10, or 20 mg/kg), ephedrine (5, 10, or 20 mg/kg), and amphetamine (0.75, 1.25, or 1.75 mg/kg) in a dose-dependent manner in rats (Hull and Maher 1990). More research is needed to determine whether L-tyrosine supplementation would produce similar results in humans.

Levodopa

Levodopa (L-dopa) may decrease tyrosine and tryptophan levels (Riederer 1980). However, administering L-dopa with tyrosine may decrease absorption of the amino acid by competitively inhibiting the transport system (Awad 1984).

Morphine Sulfate

L-tyrosine increased morphine-induced analgesia 154% in mice; only the L-form of tyrosine produced these effects (Hull et al. 1994). Further studies are needed to determine whether L-tyrosine would potentiate the analgesic activity of morphine in humans.

References

Awad AG. Diet and drug interactions in the treatment of mental illness – a review. Can J Psychiatry. 1984;29:609-613.

Hull KM, Maher TJ. L-Tyrosine potentiates the anorexia induced by mixed-acting sympathomimetic drugs in hyperphagic rats. J Pharmacol Exp Ther. 1990;255(2):403-409.

Hull KM, Tolland DE, Maher TJ. L-tyrosine potentiation of opioid-induced analgesia utilizing the hot-plate test. J Pharmacol Exp Ther. 1994;269(3):1190-1195.

Riederer P. L-Dopa competes with tyrosine and tryptophan for human brain uptake. Nutr Metab. 1980;24(6):417-423.

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