OCD suffers not responding to standard drug and CBT treatment might get greater symptom improvement with high-dose drug treatment. 
The Journal of Clinical Psychiatry has published a research article about high-dose treatment:
High-Dose Sertraline Strategy for Nonresponders to Acute Treatment for Obsessive-Compulsive Disorder: A Multicenter Double-Blind Trial Objective: To evaluate the efficacy and safety of high-dose sertraline for patients with obsessive-compulsive disorder (OCD) who failed to respond to standard sertraline acute treatment.
Method: Sixty-six nonresponders to 16 weeks of sertraline treatment who met DSM-III-R criteria for current OCD were randomly assigned, in a double-blind continuation phase of a multicenter trial, either to continue on 200 mg/day of sertraline or to increase their dose to between 250 and 400 mg/day for 12 additional weeks. Efficacy measures included the Yale-Brown Obsessive Compulsive Scale (YBOCS), the National Institute of Mental Health Global Obsessive Compulsive Scale (NIMH Global OC Scale), and the Clinical Global Impressions-Severity of Illness and -Improvement (CGI-I) scales. Data were collected from July 26, 1994, to October 26, 1995.
Results: The high-dose (250-400 mg/day, mean final dose= 357, SD = 60, N = 30) group showed significantly greater symptom improvement than the 200-mg/day group (N = 36) as measured by the YBOCS (p=.033), NIMH Global OC Scale (p = .003), and CGI-I (p = .011). Responder rates (decrease in YBOCS score of > = 25% and a CGI-I rating < = 3) were not significantly different for the 200-mg/day versus the high-dose sertraline group, either on completer analysis, 34% versus 52%, or on endpoint analysis, 33% versus 40%. Both treatments showed similar adverse event rates.
Conclusion: Greater symptom improvement was seen in the high-dose sertraline group compared to the 200-mg/day dose group during continuation treatment. Both dosages yielded similar safety profiles. Administration of higher than labeled doses of selective serotonin reuptake inhibitors may be a treatment option for certain OCD patients who fail to respond to standard acute treatment.
(J Clin Psychiatry 2006;67:15-22) The research is rather old, done back in 1995 and another thing is its sponsored by Pfizer, the maker of the SSRI sertraline (Zoloft). At the other hand high-dose treatment is not a new thing and drugs like clomipramine (Anafrenil) and paroxetine (Paxil/Seroxat) have been tested too and proven effective. Evidence-based pharmacotherapy of obsessive-compulsive disorder. Fineberg NA, Gale TM., Int J Neuropsychopharmacol. 2005 Mar;8(1):107-29. Epub 2004 Sep 28. Read the entire article at the journals homepage A qualitative analysis of nonresponse: management of treatment-refractory obsessive-compulsive disorder, Pallanti S, Hollander E, Goodman WK., J Clin Psychiatry. 2004;65 Suppl 14:6-10.
