Barlow presents results of multi-site study of CBT vs Meds in treating Panic Disorder w/o Agoraphobi

At AABT ‘98, David Barlow presented the results of a NIMH-funded multi-site study which has compared Barlow’s Panic Control Treatment (PCT) alone vs Imipramine alone vs the two in combination vs PCT plus placebo vs placebo only in the treatment of panic disorder (and I did my best to keep up with him in my note-taking). Each treatment condition consisted of 12 weeks of acute treatment (mostly weekly), 6 months monthly maintainance, and 6 months of follow-up. The study was conducted at four sites, 2 well known for CBT & two well-known for medication. The study was double-blind regarding whether patients were getting Imipramine or placebo and treatment adherence was monitored. Over 300 Ss took part in all

The study excluded patients with a history of psychosis, who were currently suicidal, currently engaged in substance abuse, who had medical contraindications to taking Imipramine, who had a history of prior non-response to either treatment, who had a pending disability claim, and who had moderate to severe agoraphobia. The study used Imipramine because that was the “state-of-the-art” medication at this time when the study was begun (it took 7 years). Agoraphobic patients were excluded because the efficacy of CBT with agoraphobic avoidance was already established.

There was a 75% completion rate for PCT & combined PCT plus Imipramine, and a slightly lower completion rate for Imipramine only. Attrition was higher than is usually seen in clinical practice because of random assignment and because the study required that Ss discontinue any medications they were on at the beginning of treatment.

At the end of the acute treatment phase PCT, Imipramine, the two in combination all worked. PCT & Imipramine were not significantly different. Combined treatment was somewhat superior. Many placebo Ss had a positive initial response but it often didn’t last. PCT plus placebo was superior to PCT alone. There was no significant difference between PCT plus Imipramine and PCT plus Placebo

After the 6 moonth maintainance period PCT ended & medication was tapered off. Follow-up analyses excluded Ss who sought additional treatment during the follow-up period). 3 ( approx 10%) placebo-only Ss did well on followup. At follow-up PCT did better than imipramine alone or PCT plus imipramine. PCT plus placebo did as well as PCT alone (it did a bit better but the difference was not statistically significant).

Overall, at follow-up (including TX dropouts) PCT did better than Imipramine, PCT was significantly better than placebo and Imipramine was not. When PCT was combined with Imipramine, this did not eliminate the problem with the durability of treatment response.

PCT and Imipramine were equivalent in producing initial treatment response. Combined treatment was somewhat superior to either alone and combining PCT with placebo did not impair effects of PCT. Imipramine produced somewhat better initial treatment response but the treatment response was not as well maintained with either Imipramine alone or Imipramine plus PCT.

Discussion by Michael Otto - The study was well designed and well done. The inclusion of the placebo plus PCT group is valuable. Would a SSRI work better? Good question for further research. For some reason, combining Imipramine with PCT interferred with maintaining the effects of PCT but combining Placebo and PCT did not. No one has figured out a good explanation of this yet. It doesn’t seem to be just a matter of attributing gains to the medication.

Discussant 2 - Critics have argued that using SSRIs, longer treatment, and more gradual tapering-off of meds would produce better results for meds. The available data from comparative research does not support the idea that SSRIs are more effective or would have a lower drop-out rate. A longer course of treatment with the medication might result in continued improvement since avoidance and cognitions are not directly addressed by meds alone and it takes time for these to change on their own. There is one small study that suggests that longer treatment with Imipramine would produce a lower relapse rate. A slower taper might improve results for meds but there is no data on this.

Which treatment is most cost-effective depends on who bears the cost of the medication. Ss tended to prefer PCT to meds. Patient preference has an impact on outcome.

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