DETERMINANTS OF PHARMACOLOGICAL TREATMENT FAILURE IN PANIC DISORDER

Background: We systematically assessed reasons for failure of pharmaco logic treatment for panic disorder in patients referred to a specialty anxiety and mood disorders clinic and examined possible determinants of treatment-resistant panic disorder. Method: Interview data were obt ained from 106 patients with DSM-III-R panic disorder seen in consulta tion. Data for each of 252 past medication trials included dose, durat ion of treatment, side effects, outcome, and reason for discontinuatio n. T tests and chi-square analyses were used to compare demographic an d clinical characteristics of patients failing versus responding to ad equate trials and those with and without intolerable medication side e ffects. Results: Of 252 medication trials, 190 used effective antipani c medications, and only 59 (23%) were adequate in dose and duration. T he most common reason for treatment failure was intolerable side effec ts, occurring in 51 (27%) of 190 trials using effective antipanic medi cations. Patients discontinuing treatment due to adverse effects had h igher Hamilton Rating Scale for Anxiety scores and were less likely to have a history of substance abuse. Discontinuation due to side effect s was significantly more common with tricyclic antidepressants than wi th benzodiazepines. True treatment resistance was reported in 14 (24%) of 59 adequate medication trials. Treatment-resistant patients were y ounger and had a higher lifetime rate of major depression. Conclusion: Although use of ineffective medications or inadequate trials were imp ortant factors, the most common reason for treatment failure was side effects, especially with tricyclic antidepressants. True treatment res istance was less common, since few medication trials were adequate in dose and duration, and may be associated with comorbidity.