Psychopharmacology Tips

Choosing between the available SSRIs for management of obsessive compulsive disorder is difficult, as their effects are very similar. In the absence of comparator data, the selection of the drug depends upon personal preference. Occasionally the possibility of a drug interaction influences the choice. Sertraline and citalopram are relatively weak inhibitors of the hepatic cytochrome P450 enzymes which metabolize many psychotropic and other medications, and may be preferred if drug interactions are likely to be a problem. Fluoxetine and paroxetine are powerful inhibitors of the CYP2D6 isoenzyme, which metabolizes tricyclic antidepressants, antipsychotics, antiarrhythmics and beta blockers. Fluvoxamine inhibits both CYP1A2, which metabolizes warfarin and tricyclics, and CYP3A4, which metabolizes benzodiazepines and some antiarrhythmics. Fluoxetine has a long half-life and an active metabolite resulting in fewer withdrawal effects, which can be advantageous for patients who forget to take their tablets

Ref: - Zohar, J. & Fineberg, N. (2001) Practical pharmacotherapy. In: Obsessive compulsive disorder: a practical guide, (Eds.) Fineberg, N., Marazzitti, D. & Stein, D.J., pp 103-117, London: Marian Dunitz.