L-methionine

Methionine/Drug Interactions:

  • Agents that elevate homocysteine levelsAgents that elevate homocysteine levels: Based on human study, methionine may increase homocysteine levels (6; 7; 13). The use of agents that elevate homocysteine levels with methionine may increase the risk of hyperhomocysteinemia. Drugs that may elevate homocysteine levels include fenofibrate, niacin, metformin, antiepileptic drugs, levodopa, and methotrexate.
  • Antineoplastic agentsAntineoplastic agents: Based on the findings of an in vitro study, a D-methionine (inactive isomer)-supplemented medium inhibited the growth of AH109A cells (hepatoma) in culture to an extent similar to that manifested in a methionine-free medium (25). In mice, methionine depletion increased the efficacy of cisplatin against the MX-t human breast carcinoma cell line (11) and significantly enhanced the antitumor activity of 5-fluorouracil against the SC-1-NU human gastric cancer xenograft by approximately twofold (12). Synergy between methionine restriction and 5-fluorouracil may be attributable to multiple factors, including depletion of reduced folates, selective inhibition of thymidylate synthase, and creation of an imbalanced nucleotide pool (26).
  • Hepatotoxic agentsHepatotoxic agents: Based on animal and human study, failure to maintain homeostasis of the methionine cycle and accumulation of methionine may result in liver damage (20; 14; 21). Theoretically, concurrent use of methionine and hepatotoxic agents may increase the risk of liver damage.

    • Methionine/Herb/Supplement Interactions:

  • Agents that elevate homocysteine levelsAgents that elevate homocysteine levels: Based on human study, methionine may increase homocysteine levels (6; 7; 13). The use of agents that elevate homocysteine levels with methionine may increase the risk of hyperhomocysteinemia.
  • AntineoplasticsAntineoplastics: Based on the findings of an in vitro study, a D-methionine-supplemented medium inhibited the growth of AH109A cells (hepatoma) in culture to an extent similar to that manifested in a methionine-free medium (25). In mice, methionine depletion increased the efficacy of cisplatin against the MX-t human breast carcinoma cell line (11) and significantly enhanced the antitumor activity of 5-fluorouracil against the SC-1-NU human gastric cancer xenograft by approximately twofold (12). Synergy between methionine restriction and 5-fluorouracil may be attributable to multiple factors, including depletion of reduced folates, selective inhibition of thymidylate synthase, and creation of an imbalanced nucleotide pool (26).
  • Hepatotoxic herbsHepatotoxic herbs: Based on animal and human study, failure to maintain homeostasis of the methionine cycle and accumulation of methionine may result in liver damage (20; 14; 21). Theoretically, concurrent use of methionine and hepatotoxic agents may increase the risk of liver damage.

    • Methionine/Food Interactions:

  • Methionine-containing foods (red meat, chicken)Methionine-containing foods (red meat, chicken): Based on human study, methionine may increase homocysteine levels (6; 7; 13). Consumption of foods that contain large amounts of methionine, such as red meat and chicken, along with methionine may increase the risk of hyperhomocysteinemia.

    • Methionine/Lab Interactions:

  • Aspartate transaminase (AST)Aspartate transaminase (AST): Patients with acetaminophen toxicity who were administered methionine exhibited a subsequent increase in mean maximum serum aspartate transaminase (AST) activity (294 IU/L) compared to a mean maximum level of more than 2,000 IU/L in patients given only supportive treatment (4).
  • Plasma homocysteine concentrationsPlasma homocysteine concentrations: In human experimentation, very high doses of supplementary methionine have been shown to cause increased plasma concentrations of homocysteine (hyperhomocysteinemia) (6; 7; 13).
  • Urinary ethylmalonic acidUrinary ethylmalonic acid: A case report showed that loading with methionine (100mg/kg) increased the excretion of ethylmalonic acid in infants with ethylmalonic acid encephalopathy with petechiae (27).