A Naturalistic Long-Term Comparison Study of Selective Serotonin Reuptake Inhibitors in the Treatment of Panic Disorder

Objectives: Selective serotonin reuptake inhibitors (SSRIs) are currently considered as the first drug of choice in the treatment of panic disorder (PD). The aim of this long-term, naturalistic comparison study was to compare 4 SSRIs with respect to tolerability and treatment outcome of PD. Outcome measures included relapse rates and adverse effects. Methods: Two hundred patients with PD were enrolled in our study. All subjects met DSM-IV criteria for PD or PD with agoraphobia (PDA). All patients were assigned to receive SSRI monotherapy for 12 months with either citalopram (n = 50), fluoxetine (n = 50), fluvoxamine (n = 50), or paroxetine (n = 50) in a randomized, nonblinded fashion. Both the treating psychiatrist and the patients were not blind to the assigned treatment, but the clinician raters were blind to the study medication. The study design allowed for assignment of a particular SSRI as indicated according to the clinical judgment of the study psychiatrists. The Panic Self-Questionnaire, which is a self-report scale, was administered at baseline and then once per month during the duration of the 12-month study. The visual analog scale and the Clinical Global Impression Scale were administered at baseline and then once per month during the period of the study. Reports of sexual dysfunction were assessed using a nonstructured clinical interview at monthly visits. The body weight of study subjects was measured at baseline, and then at the 12th month visit end point. Results: Of 200 patients who entered the study, 127 patients (63.5%) completed the full 12-month protocol. Retention rates were highest for paroxetine (76% [38/50]), intermediate for citalopram (68% [34/50]) and fluvoxamine (60% [30/50]), and lowest for fluoxetine (50% [25/50]). Patients who completed the 12-month protocol responded favorably to the study treatment. The paroxetine and the citalopram groups had significantly lower rates of panic symptoms as measured at visits on weeks 4 and 8. At visits on months 3, 6, 9, and 12, however, there were no statistically significant differences between the 4 groups in relapse rates (defined as the occurrence of 1 or more panic attacks during the previous week of treatment) (F1,127 = 0.17; P = 0.13 [not statistically significant]). At the 12th month end point, patients in all 4 treatment groups had a statistically significant increase in body weight. Body weight among the study population increased by 6.1 + 4.9 kg from a mean weight of 72.4 + 7.3 kg at the onset of treatment. Reports of sexual adverse effects at the 12th month visit were similar in the citalopram, fluoxetine, and paroxetine groups, but the fluvoxamine patient group reported fewer sexual adverse effects at the 12th month visit. Conclusions: Most of our PD patients responded well to 12-month treatment with either citalopram, fluoxetine, fluvoxamine, or paroxetine, and the overall response rate was equal after the first 4 weeks of treatment. Although patients treated with paroxetine had the lowest dropout rates during the initiation phase, they had the highest rate of adverse effects as measured at the 12th month visit. Conversely, patients in the fluvoxamine group had the highest dropout rate (which was primarily caused by adverse effects in the initiation phase of treatment.); however, patients who were able to tolerate fluvoxamine throughout the full course of the study were observed to have lower rates of sexual dysfunction and weight gain compared with patients treated with the other agents. Overall, when measured at the 12th month visit, monotherapy with paroxetine and citalopram was associated with a higher rate of sexual adverse effects than was treatment with fluoxetine or fluvoxamine. In addition, monotherapy with paroxetine, citalopram, and fluoxetine seemed to cause more weight gain than did treatment with fluvoxamine.