The use of psychotropic medications has become popular in the treatment of functional bowel disorders, especially the IBS. Both the tricyclic antidepressant medications (TCAs), as well as the selective serotonin reuptake inhibitors (SSRIs), can be used in IBS; however, the TCA medications have been more extensively evaluated for this purpose and may be more efficacious.
There is a separate chapter on the use of psychotropic drugs in patients with functional disorders (see Chapter 43, "Psychotropic Drugs and Management of Patients with Functional Gastrointestinal Disorders").
When choosing an antidepressant for therapy, the side effect profile should be used to the patient's advantage. In IBS patients with diarrhea,a TCA would be more appropriate given its side effect of constipation. Conversely, an SSRIshould be chosen in IBS patients with constipation. When choosing a specific TCA, use a secondary amine with fewer overall side effects such as nortriptyline (Pamelor) instead of its precursor amitriptyline (Elavil) or desipramine (Norpramin) instead of imipramine (Tofranil). Low doses of the TCAs between 10 and 25 mg are used initially with the maximum benefit usually occurring at a dose of 50 mg/d (see Table 39-1).
Little data are currently available about the SSRI antidepressant medications. However, preliminary studies have suggested possible efficacy with the use of paroxetine (Paxil) (Creed et al, 2001), as well as fluoxetine (Prozac) (Kurken et al, 2002). Standard antidepressant doses of these SSRI medications may be necessary. Preliminary evidence suggests that the use of naloxone, an opioid receptor antagonist, may be useful in the treatment of pain in IBS patients with constipation, but larger scale studies are required before this recommendation can be made (Hawkes et al, 2002). As will be discussed below, the 5-HT receptor agonists and antagonists can also be used in the proper circumstances for the treatment of pain.
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