High blood pressure may occur in susceptive individuals — hypertensive patients taking tyrosine should be monitored closely.
AMPHETAMINE, EPHEDRINE, PHENYLPROPANOLAMINE
L-tyrosine (200 and 400 mg/kg) has been shown to increase the side-effect of anorexia caused by phenylpropanolamine, ephedrine and amphetamine in a dose-dependent manner in rats — observe patients using this combination.
Monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants or selective serotonin reuptake inhibitor drugs (SSRIs) Theoretically, concurrent use may result in elevated blood pressure and/or enhanced antidepressant effects. In the case of MAOIs some tyrosine may be metabolised to tyramine and concurrent use with MAOIs may lead to hypertensive crisis.
Tyrosine should be avoided unless under medical supervision.
Tyrosine is a precursor to a number of neurotransmitters so additive effects may occur — caution.
L-dopa competes with tyrosine for uptake, therefore concurrent use may decrease uptake of both substances, thereby reducing efficacy — avoid unless under medical supervision.
L-tyrosine potentiates morphine-induced analgesia 154% in mice. Observe patients taking tyrosine and morphine sulfate concurrently — potential beneficial interaction.
THYROID HORMONE MEDICATION
Additive effects possible because tyrosine is a precursor to thyroid hormones — observe patients taking tyrosine concurrently with thyroid hormone medication.
Contraindications and Precautions
• Malignant melanoma: a theoretical concern exists that tyrosine supplementation may promote the division of cancer cells. Tyrosine is contraindicated until safety is established.
• Manic conditions: due to the theoretical possibility that tyrosine may significantly increase neurotransmitter synthesis, close medical supervision is required.
• Hyperthyroidism and Graves’ disease: theoretically tyrosine may aggravate these conditions as it is a precursor to thyroxine.
• Alkaptonuria and tyrosinaemia (inborn errors of tyrosine metabolism).
• Hypertension: use tyrosine with caution at high dose.
Not recommended during pregnancy.