Final answer:
Clomipramine is the tricyclic antidepressant with better efficacy for treating OCD when SSRIs are not effective, as it increases serotonin levels in the central nervous system.
Step-by-step explanation:
The tricyclic antidepressant that has been shown to have significantly better efficacy in treating Obsessive-Compulsive Disorder (OCD) than the others is Clomipramine. While selective serotonin reuptake inhibitors (SSRIs) like Prozac, sertraline, and paroxetine are typically first-line treatments for OCD, Clomipramine is a tricyclic antidepressant that has been found useful when SSRIs do not achieve the desired results. This drug functions by blocking the reuptake of serotonin, thereby increasing the levels of serotonin in the central nervous system, which is beneficial for patients with OCD.