Antidepressants

Antidepressants are commonly used as a treatment option for patients with irritable bowel syndrome with diarrhea (IBS-D). Some antidepressants have also shown to be effective at low doses in patients with IBS with constipation (IBS-C).1,2 Antidepressants, while initially developed to treat depression, have been shown to be effective in treating pain and symptoms from functional GI disorders, like IBS.3

In addition to the disturbances in intestinal motility (resulting in either diarrhea or constipation) and abdominal pain that are experienced by patients with IBS, recent studies have also shown that the normal function of the brain being able to “turn down” pain signals sent from the gut is impaired. The pain can become severe when the patient is experiencing emotional distress, which may occur due to stresses in life or due to the stress and frustration of IBS symptoms. Antidepressants can help the brain-gut dysfunction of IBS.3

There are different kinds of antidepressants, categorized for how they work in the body. Those often used in the treatment of IBS include:

  • Tricyclic Antidepressants
  • Selective Serotonin Reuptake Inhibitors
  • Serotonin-Norepinephrine Reuptake Inhibitors1,2

Tricylic Antidepressants for IBS Treatment

Tricyclic antidepressants (TCAs) work by affecting the naturally occurring chemical messengers, called neurotransmitters, in the brain and body. TCAs block the absorption (or reuptake) of the neurotransmitters serotonin and norepinephrine. In clinical trials, patients with IBS-D who took a low-dose TCA experienced a significant reduction in the number of loose stool and the feeling of incomplete bowel movements compared to patients who were taking a placebo (harmless pill that produces no physical effects). TCAs also have an effect on the neurotransmitter acetylcholine, which is involved in muscle spasms of smooth muscle like those found in the intestines. Because of this effect, they may cause constipation, and are better suited for patients with IBS-D. However, they can be effective without significant side effects at lower doses in patients with IBS-C.1,3,4
TCAs have been available and on the market for many years and are relatively inexpensive. Some TCAs used in the treatment of IBS include:

  • Amitriptyline (Elavil)
  • Imipramine (Tofranil)
  • Desipramine (Norpramin)
  • Nortriptyline (Pamelor), as well as others.3

Patients taking TCAs may experience the following side effects: dry mouth, difficulty sleeping at times, difficulty urinating, sexual difficulties, constipation, dizziness and/or drowsiness.3

Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors (SSRIs) target the neurotransmitter serotonin and have been shown to promote global well being in some patients with IBS as well as improve some of the abdominal pain and bowel symptoms. Some SSRIs have proven effective in treating pain in a number of conditions, but the effectiveness of SSRIs on the gut have not been clearly proven in research. The exact ways SSRIs work in IBS are not completely understood by the scientific and medical community.5
SSRIs include:

  • Citalopram (Celexa)
  • Escitalopram (Lexapro)
  • Paroxetine (Paxil)
  • Sertraline (Zoloft)
  • Fluoxetine (Prozac)

Patients taking SSRIs may experience side effects, such as nervousness, vivid dreams, sleep disturbances, sexual difficulties, and/or diarrhea.3

Serotonin-Norepinephrine Reuptake Inhibitors

Serotonin-norepinephrine reuptake inhibitors (SNRIs) block the absorption of the neurotransmitters serotonin and norepinephrine and have proven effective in many pain-related disorders. In addition, like other antidepressants, they help with overall mood.3
SNRIs include:

  • Venlafaxine (Effexor)
  • Duloxetine (Cymbalta)
  • Desvenlavaxine (Pristiq)
  • Milnacipram (Savella)

Common side effects experienced by patients taking SNRIs include nausea, headache, and rarely, changes in liver chemistry tests.3

A Comparison of Antidepressants for the Treatment of IBS6

TCAs
SSRIs
SNRIs
Agentst
Amitriptyline, Imipramin, Doxepin, Desirpramine, Nortiptyline
Fluoxetine, Sertraline, Paroxetine, Citalopram
Duloxetine, Venlafaxine, Desvenlafaxine
Possible side effects
Sedation, Constipation, Dry mouth/eyes, Weight gain, Low blood pressure, Sexual dysfunction
Insomnia, Diarrhea, Night sweats, Weight loss, Agitation, Sexual dysfunction
Nausea, Agitation, Dizziness, Fatigue, Liver dysfunction
Time to action
Few days to 2 weeks (low doses)
2-6 weeks (high doses)
3-6 weeks
3-6 weeks
Efficacy in IBS
Good
Moderate
Not adequately studied
Pain modulation
++
?
++
Motility
++
+
?
Visceral pain
+++
?
?
Sleep
++
?
Mood disorders
++
+++
+++

Other Treatment Options for IBS

Patients with IBS often have to try several treatment options before finding the right combination of approaches that work best to manage their symptoms. In addition to antidepressants, patients can try a variety of lifestyle approaches – including dietary changes, exercise, adding fiber or probiotics, and managing their stress levels – or other medications such as antispasmodics, antibiotics, antidiarrheals, and laxatives.

Written by: Emily Downward | Last reviewed: June 2016.
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