Most patients easily tolerate an initial dose of 20 mg, administered once daily. This dose can be taken in the morning or at night depending on the individual’s side effect profile, because some patients may develop insomnia or other sleep disturbance in contrast to the more commonly reported somnolence. It is not necessary to take citalopram with food. Because there are only limited published data on dosing in obsessive-compulsive disorder (OCD), no optimal dose has been established for this condition. However, based on the studies reviewed above, 40-60 mg/day appears reasonable. Moreover, this dose range is consistent with data on other SSRIs for which fixed-dose studies in obsessive-compulsive disorder have typically found the best response at the higher end of the dose range (). Based on the same reasoning, patients should probably be treated for a minimum of 10 weeks, including at least 4-6 weeks at a maximum dose, before being considered “nonresponders” to citalopram or any other SSRI agent (). A case report by Bejerot and Bodlund (1998) raised the possibility of increased efficacy with considerably higher doses, suggesting that higher doses may represent an alternative in individuals with otherwise treatment-resistant OCD.
Citalopram is also available in parenteral form, although this form is not currently approved for use in the United States. A double-blind trial of oral dose after an initial infusion period compared citalopram favorably with viloxazine, a noradrenergic antidepressant (). One study has compared oral dosing with an initial slow-drop infusion for 10 days followed by oral form in a group of moderately to severely depressed patients. Although no significant differences were found between the groups, a trend was observed toward faster response (defined as a greater than 50% reduction in Ham-D score) in patients who received the infusion initially (33.3%) compared with those receiving the oral treatment (17.9%) (). Intravenous administration is generally well tolerated and may prove in the future to be a valuable alternative in some populations. No studies of intravenous use in obsessive-compulsive disorder are yet available, although one might assume similar positive responses as seen with clomipramine ().
Although definitive conclusions should await peer-reviewed results of large double-blind trials, it seems clear that citalopram appears to help obsessive-compulsive disorder in adults as well as children and adolescents. The small comparative study by Mundo et al. (1997), which reported efficacy for subjects receiving citalopram comparable with that for subjects receiving the SSRIs fluvoxamine and paroxetine, indicates that citalopram may well represent a valid alternative to current first-line treatments for OCD. Moreover, it may offer some advantages as compared with other agents in its class in terms of tolerability and low capacity for drug-drug interactions. It appears that the therapeutic dose range will likely be comparable with, or slightly higher than, that reported for depression, but the absence of published data from fixed-dose trials makes it premature to come to any conclusions as yet. There are as yet no data on longer-term outcomes. This problem plagues our knowledge of all of the available first-line drugs but will hopefully be addressed in the years to come.
Selections from the book: “Current treatments of obsessive-compulsive disorder” (2001).