L-threonine

L-threonine/Drug Interactions:

  • Alzheimer's agentsAlzheimer's agents: According to secondary sources, threonine may decrease the effectiveness of NMDA antagonists.
  • AnalgesicsAnalgesics: In clinical research, headaches have been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with analgesics used to treat headaches.
  • AntilipemicsAntilipemics: In animal research, threonine has been shown to act as a lipotropic agent, which controls fat buildup in the liver (15). Theoretically, L-threonine may interact with antilipemic agents.
  • Dermatologic agentsDermatologic agents: In clinical research, skin warmth and rash have been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with dermatologic agents.
  • Gastrointestinal agentsGastrointestinal agents: Indigestion (N=1) and diarrhea (N=1) occurred in clinical research in patients with spinal spasticity (7). In clinical research, flatus and constipation occurred with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. According to secondary sources, side effects may include stomach upset and nausea. Theoretically, L-threonine may interact with gastrointestinal agents.
  • Medroxyprogesterone acetateMedroxyprogesterone acetate: In protein-supplemented humans (including L-threonine), medroxyprogesterone acetate reduced blood levels of threonine compared with the protein supplement alone (3).
  • Muscle relaxantsMuscle relaxants: In human research, L-threonine improved disability scores in patients with muscle spasticity (13; 7). Theoretically L-threonine may interact with muscle relaxants.
  • Nasal decongestantsNasal decongestants: In clinical research, rhinorrhea has been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with nasal decongestants.
  • Neurological agentsNeurological agents: Threonine is a precursor to the amino acid glycine, an inhibitory neurotransmitter in the spinal cord. Threonine is thought to penetrate the central nervous system prior to conversion to glycine (16). Theoretically L-threonine may interact with neurological agents.
  • NMDA antagonistsNMDA antagonists: According to secondary sources, threonine may decrease the effectiveness of NMDA antagonists.

    • L-threonine/Herb/Supplement Interactions:

  • GeneralGeneral: According to secondary sources, L-threonine may aid in the absorption of nutrients.
  • Alzheimer's agentsAlzheimer's agents: According to secondary sources, threonine may decrease the effectiveness of NMDA antagonists. Theoretically, L-threonine may interact with other Alzheimer's agents.
  • AnalgesicsAnalgesics: In clinical research, headaches have been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with analgesics used to treat headaches.
  • AntilipemicsAntilipemics: In animal research, threonine has been shown to act as a lipotropic agent, which controls fat buildup in the liver (15). Theoretically, L-threonine may interact with antilipemic agents.
  • DecongestantsDecongestants: In clinical research, rhinorrhea has been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with nasal decongestants.
  • Dermatologic agentsDermatologic agents: In clinical research, skin warmth and rash have been reported with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. Theoretically, L-threonine may interact with dermatologic agents.
  • Gastrointestinal agentsGastrointestinal agents: Indigestion (N=1) and diarrhea (N=1) occurred in clinical research in patients with spinal spasticity (7). In clinical research, flatus and constipation occurred with L-threonine plus pyridoxal-5-phosphate supplementation (14); however, the effects of L-threonine alone are unclear from this study. According to secondary sources, side effects may include stomach upset and nausea. Theoretically, L-threonine may interact with gastrointestinal agents.
  • L-tryptophanL-tryptophan: In human research, use of a tryptophan-free amino acid mixture, containing L-threonine, reduced plasma levels of tryptophan (17). However, clinical significance is lacking, as the authors concluded this was due to the lack of tryptophan as opposed to the inclusion of L-threonine.
  • Muscle relaxantsMuscle relaxants: In human research, L-threonine improved disability scores in patients with muscle spasticity (13; 7).
  • Neurological agentsNeurological agents: Threonine is a precursor to the amino acid glycine, an inhibitory neurotransmitter in the spinal cord. Threonine is thought to penetrate the central nervous system prior to conversion to glycine (16). Theoretically L-threonine may interact with neurological agents.

    • L-threonine/Food Interactions:

  • GeneralGeneral: According to secondary sources, L-threonine may aid in the absorption of nutrients.
  • L-tryptophanL-tryptophan: In human research, use of a tryptophan-free amino acid mixture, containing L-threonine, reduced plasma levels of tryptophan (17). However, clinical significance is lacking, as the authors concluded this was due to the lack of tryptophan as opposed to the inclusion of L-threonine.

    • L-threonine/Lab Interactions:

  • GlycineGlycine: Threonine supplementation has been reported to be converted in the body to glycine (16). However, in human research, effects of threonine supplementation on plasma and cerebrospinal fluid glycine levels were lacking (12; 13).
  • L-tryptophanL-tryptophan: In human research, use of a tryptophan-free amino acid mixture, containing L-threonine, reduced plasma levels of tryptophan (17). However, clinical significance is lacking, as the authors concluded this was due to the lack of tryptophan as opposed to the inclusion of L-threonine.
  • ThreonineThreonine: In human research, threonine supplementation increased plasma and cerebrospinal fluid levels of threonine (12; 13; 7).