With respect to antidepressants both selective serotonin reuptake inhibitors and tricyclic antidepressants appear useful. Pharmacological therapy mainly uses activating substances such as tricyclic antidepressants or methylphenidate. The tricyclic antidepressants (TCAs) inhibit the reuptake of both serotonin and norepinephrine. Xylazine is very similar to drugs such as phenothiazine, tricyclic antidepressants, and clonidine. Benzodiazepines are not significantly better for insomnia than antidepressants. Onset of action appears faster than some SSRIs and similar to tricyclic antidepressants. There is good evidence that low doses of tricyclic antidepressants can be effective for IBS. Medications, such as antidepressants or beta blockers, may improve symptoms. NSAIDs may interfere and reduce efficiency of SSRI antidepressants. Medications include Antidepressants, Anti-psychotics, Anti-seizure and Beta blockers. Bupropion is less likely than other antidepressants to cause sexual dysfunction. SSRIs are the most widely prescribed antidepressants in many countries. Adjunct medications are an umbrella category of substances that increase the potency or "enhance" antidepressants. There is less data on fluoxetine than on antidepressants as a whole. Duloxetine appears less tolerable than some other antidepressants.