Postmarketing surveillance by patient self-monitoring: preliminary data for sertraline versus fluoxetine

There have been no published postmarketing reports comparing sertraline with another serotonin selective reuptake inhibitor (SSRI) in large-sample, parallel groups. As part of an ongoing postmarketing surveillance study, this paper presents preliminary data for a number of adverse clinical events reported by outpatients being treated with either fluoxetine or sertraline.

Using a well-validated method developed to signal possible adverse drug reactions, data were collected on 1577 fluoxetine-treated and 1209 sertraline-treated patients who filled a prescription for either of the two targeted drugs. Pharmacists gave these patients an announcement, part of which served as an entry form, that described the purpose and details of the study. Volunteers (highly selective) were requested to report during the next month via a toll-free telephone interview "any new or unusual symptoms or unexpected improvements" in their health since starting the designated medication.

Almost 1 (31.4%) of every 3 sertraline-treated patients called at least once to report one or more adverse clinical events compared with only about 1 (19.7%) of every 5 fluoxetine-treated patients. Most of the reported adverse clinical events--but not all--are well-known adverse drug reactions that seem common to SSRIs. Adverse clinical events reported more frequently by sertraline-treated patients included urinary, sexual, psychological, neurologic, gastrointestinal, and dermatological complaints. Drug discontinuation was also reported more frequently by sertraline-treated patients. Fluoxetine-treated patients reported an increased frequency of weight gain and anger or aggression.

These data indicate that many adverse reactions known to be induced by fluoxetine are being reported with even greater frequency by sertraline-treated patients. Possible interpretations of these differences are discussed.