WASHINGTON — Depressed patients with infections who were treated concomitantly with linezolid and antidepressants showed no evidence of developing serotonin syndrome due to drug interactions, compared with similar patients taking other antibiotics, Dr. Meryl H. Mendelson of Pfizer Global Pharmaceuticals, New York, and colleagues reported in a poster presented at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
Despite this evidence against dangerous drug interactions, data from postmarketing case reports suggest the need to closely observe patients on linezolid and concomitant antidepressants. Physicians should consider discontinuing one or both if patients show signs or symptoms of serotonin syndrome, the investigators said.
Limited clinical evidence suggests that linezolid may weakly inhibit monoamine oxidase and may interact with adrenergic or serotonergic agents, they noted.
A total of 117 adults who received SSRIs and linezolid were matched with 127 patients who received SSRIs and non-linezolid antibiotics—including amoxicillin-clavulanate, cefadroxil, and vancomycin—in phase III and IV drug comparison trials.
Among additional patients being treated with tricyclic or other non-SSRI antidepressants, 112 patients receiving linezolid were matched with 115 patients receiving non-linezolid antibiotics. Both groups were treated concomitantly with antibiotics for approximately 8 days.
Symptoms were classified in three groups based on directly observed or patient-reported adverse events. (See chart.) Adverse event rates were similar among patients on linezolid and other antibiotics.
The study was sponsored by Pfizer, and the meeting was sponsored by the American Society for Microbiology.