Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect or predict the rates observed in practice.

Multiple doses of fluoxetine have been administered to 10,782 patients with various diagnoses in US clinical trials. Adverse reactions were recorded by clinical investigators using descriptive terminology of their own choosing. Consequently, it is not possible to provide a meaningful estimate of the proportion of individuals experiencing adverse reactions without first grouping similar types of reactions into a limited (that is, reduced) number of standardized reaction categories.

In the tables and tabulations that follow, COSTART Dictionary terminology has been used to classify reported adverse reactions. The stated frequencies represent the proportion of individuals who experienced, at least once, a treatment-emergent adverse reaction of the type listed. A reaction was considered treatment-emergent if it occurred for the first time or worsened while receiving therapy following baseline evaluation. It is important to emphasize that reactions reported during therapy were not necessarily caused by it.

The prescriber should be aware that the figures in the tables and tabulations cannot be used to predict the incidence of side effects in the course of usual medical practice where patient characteristics and other factors differ from those that prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different treatments, uses, and investigators. The cited figures, however, do provide the prescribing physician with some basis for estimating the relative contribution of drug and nondrug factors to the side effect incidence rate in the population studied.

Incidence in placebo-controlled PMDD clinical trials — In 1 of 3 placebo-controlled, continuous-dosing trials and 1 placebo-controlled, intermittent-dosing trial of fluoxetine in PMDD, treatment-emergent adverse reactions reporting rates were assessed. The information contained in Table 5 enumerates the most common treatment-emergent adverse reactions associated with the use of fluoxetine tablet 20 mg (incidence of at least 5% for fluoxetine tablet 20 mg and greater than placebo) for the treatment of PMDD and is based on data from the continuous-dosing trial at the recommended dose of fluoxetine tablet (fluoxetine tablets 20 mg, N = 104; placebo, N = 108) and data from the intermittent-dosing trial of fluoxetine in PMDD (fluoxetine tablets 20 mg, N = 86; placebo, N = 88).

Incidence in US depression, OCD, and bulimia placebo-controlled clinical trials (excluding data from extensions of trials) — Table 6 enumerates the most common treatment-emergent adverse reactions associated with the use of fluoxetine up to 80 mg (incidence of at least 2% for fluoxetine and greater than placebo) in female patients ages 18 to 45 years from US placebo-controlled clinical trials in the treatment of depression, OCD, and bulimia.

Adverse reactions associated with discontinuation in two placebo-controlled PMDD clinical trials — In a continuous-dosing PMDD placebo-controlled trial, the most common adverse reaction (incidence at least 2% for fluoxetine tablet 20 mg and greater than placebo) associated with discontinuation was nausea (3% for fluoxetine tablet 20 mg, N = 104 and 1% for placebo, N = 108). In an intermittent-dosing placebo-controlled trial, no reactions associated with discontinuation reached an incidence of 2% for fluoxetine tablet 20 mg. In these clinical trials, more than one reaction may have been recorded as the cause of discontinuation.

Adverse reactions associated with discontinuation in depression, OCD, and bulimia placebo-controlled US clinical trials (excluding data from extensions of trials) — In female patients age 18 to 45 years in US depression, OCD, and bulimia placebo-controlled clinical trials combined, which collected a single primary reaction associated with discontinuation (incidence at least 1% for fluoxetine and at least twice that for placebo), insomnia (1%, N = 561) was the only reaction reported.

Female sexual dysfunction with SSRIs — Although changes in sexual desire, sexual performance, and sexual satisfaction often occur as manifestations of a mood-related disorder, they may also be a consequence of pharmacologic treatment. In particular, some evidence suggests that SSRIs can cause such untoward sexual experiences. Reliable estimates of the incidence and severity of untoward experiences involving sexual desire, performance, and satisfaction are difficult to obtain, however, in part because patients and physicians may be reluctant to discuss them. Accordingly, estimates of the incidence of untoward sexual experience and performance, cited in product labeling, are likely to underestimate their actual incidence. For example, in women (age 18 to 45) receiving fluoxetine for indications other than PMDD, decreased libido was seen at an incidence of 4% for fluoxetine compared with 1% for placebo. There have been spontaneous reports in women (age 18 to 45) taking fluoxetine for indications other than PMDD of orgasmic dysfunction, including anorgasmia.

There are no adequate and well-controlled studies examining sexual dysfunction with fluoxetine treatment. While it is difficult to know the precise risk of sexual dysfunction associated with the use of SSRIs, physicians should routinely inquire about such possible side effects.