Tricyclic and SSRIs(Selective Serotonin Reuptake Inhibitator) are types of anti-depressants. Both types of antidepressants are usually used to relieve IBS symptoms such as depression or pain. These are drugs that must be prescribed by a doctor & each doctor seems to have their own preferences as to which drugs they prescribe. Not everyone responds to the same antidepressant or antidepressants in general.
5-HTP is an alternative to typical antidepressants & is available without a prescription.