Serotonin Toxicity and Urinary Analgesics: A Case Report and Systematic Literature Review of Methylene Blue-Induced Serotonin Syndrome.

BACKGROUND: Serotonin syndrome (SS) is a potentially serious side effect of serotonergic drugs. Cases of SS have been reported from the administration of methylene blue (MB), an agent with monoamine oxidase inhibiting properties. To date, the reported cases of MB-induced SS have all been with MB given parenterally. We report a case induced by the initiation of a MB-containing oral agent.

METHODS: A case of SS felt to be induced by the initiation of an MB-containing orally-administered urinary analgesic, started in a patient concurrently treated with multiple serotonergic drugs, is presented. A systematic literature review of MB-induced SS follows. The review consisted of searches in MEDLINE databases using the key terms "methylene blue" and "serotonin syndrome". The authors read all abstracts, and articles related to MB and serotonin toxicity; non-associated articles were discarded. Results are summarized.

RESULTS: 23 manuscripts were identified, resulting in 50 unique cases of MB-induced SS. The majority of cases were related to peri-operative use of MB in parathyroidectomies or for the treatment of vasoplegic shock. All cases were associated with MB given parenterally. Concurrent treatment with serotonergic antidepressants was described in all 50 cases. Symptoms of SS ranged from mild to severe. One fatality was reported.

CONCLUSIONS: Methylene blue can induce SS, felt to be secondary to MAOI properties. Although previous reports have exclusively been associated with MB given via parental administration, our case suggests that SS can be induced by oral administration of MB-containing agents.