Why Antidepressants Are Used for IBS

You might be wondering why your doctor would prescribe an antidepressant for your irritable bowel syndrome (IBS) if you are not depressed.

Or, perhaps like many people, you do have depression or anxiety alongside your IBS, so it makes more sense, but you still don't understand what effects an antidepressant might have on your IBS symptoms.

The following overview will answer the question of why antidepressants are sometimes used as a treatment for IBS and educate you as to the types of antidepressants that are commonly prescribed to IBS patients.

Antidepressants and IBS

Although medications in this class are labeled as antidepressants, they have effects that go beyond stabilizing a depressed mood. Antidepressants have been shown to reduce anxiety and pain sensations while having positive effects on the digestive system.

Doctors may prescribe an antidepressant to someone with IBS, but this is considered an "off-label" use of the drug, as no antidepressant has received FDA approval as an IBS treatment.

However, the American College of Gastroenterology, after an extensive research review, concluded that there is enough research support on the effectiveness of two classes of drugs to recommend their use in treating IBS.

Specifically, antidepressants have been found to have a positive effect on gut motility and visceral hypersensitivity. It's hypothesized that these beneficial effects come from the action of these medications on the neurotransmitters found in the brain and the gut.

Antidepressants used for IBS generally fall into one of the following classes.

• Tricyclic antidepressants (TCAs)
• Selective serotonin reuptake inhibitors (SSRIs)

Tricyclic Antidepressants

TCAs are the elder statesmen of antidepressants. They have well-documented anti-pain and gut-slowing qualities, which seems due to their actions on the neurotransmitters serotonin and norepinephrine. This slowing down of gut motility makes the TCAs better suited for the treatment of diarrhea-predominant IBS (IBS-D).

Unfortunately, the same action (anticholinergic effect) that slows down the intestinal tract can occasionally lead to side effects, including:

• Drowsiness
• Dry mouth
• Blurred vision
• Sexual problems
• Dizziness
• Tremors
• Headache
• Weight gain

TCAs that might be prescribed for IBS include:

• Elavil (amitriptyline)
• Tofranil (imipramine)
• Norpramin (desipramine)
• Aventyl, Pamelor, Allegron (nortriptyline)

Selective Serotonin Reuptake Inhibitors

SSRIs were designed to increase the level of the neurotransmitter serotonin in the nervous system, so as to facilitate a beneficial effect on mood. Because they only target serotonin, SSRIs generally have fewer side effects than TCAs.

Side effects are common but often go away as your body adjust to the medication. Possible side effects include:

• Nausea
• Diarrhea
• Anxiety
• Headache

The lack of a constipating effect makes the SSRIs a better choice for those with constipation predominant IBS (IBS-C).

SSRIs may also result in prolonged side effects of sexual difficulties (loss of sex drive and/or difficulty achieving orgasm) and weight gain. People react differently to medications and you may tolerate one type of SSRI better than another.

Examples of commonly prescribed SSRIs include:

• Celexa (citalopram)
• Lexapro (escitalopram oxalate)
• Prozac (fluoxetine)
• Paxil (paroxetine)
• Zoloft (sertraline)

5-HT3 for Depression

Researchers have looked at medications that target specific serotonin receptor sites known as 5-HT3 receptors. The controversial Lotronex falls into this category.

Due to the risk of serious side effects, the FDA has imposed strict limits on the prescription of Lotronex. There is one 5-HT3 antidepressant, Remeron (mirtazapine). Data is limited as to the effectiveness of Remeron for IBS and therefore it may be less commonly prescribed.