Some of the more effective and commonly used medications for chronic pain are drugs that were developed to control other conditions. Antidepressants are a mainstay in the treatment of many chronic pain conditions — even when depression isn’t a factor.

Tricyclics used most often

Tricyclic antidepressants are the most common type used for pain. They include:

• Amitriptyline
• Imipramine (Tofranil)
• Clomipramine (Anafranil)
• Nortriptyline (Pamelor)
• Desipramine (Norpramin)
• Doxepin (Sinequan)

Types of pain relieved

Tricyclic antidepressants seem to work best for pain caused by:

• Nerve damage from diabetes (diabetic neuropathy)
• Nerve damage from shingles (postherpetic neuralgia)
• Tension headache
• Migraine
• Fibromyalgia
• Low back pain

The painkilling mechanism of these drugs is still not fully understood. Tricyclic antidepressants may increase neurotransmitters in the spinal cord that reduce pain signals. But they don’t work immediately. You may have to take a tricyclic antidepressant for several weeks before it starts reducing your pain.

Side effects usually mild

Side effects of tricyclic antidepressants may include:

• Drowsiness
• Dry mouth
• Constipation
• Weight gain
• Difficulty with urination
• Changes in blood pressure

To reduce or prevent side effects, your doctor will likely start you at a low dose and slowly increase the amount. Most people are able to take tricyclic antidepressants, particularly in low doses, with only mild side effects. The doses that are effective for pain are typically lower than the doses used for depression.

Other antidepressants that may help

Drugs such as venlafaxine (Effexor) and duloxetine (Cymbalta) can relieve many of the same types of painful conditions that are eased by tricyclic antidepressants. Known as serotonin and norepinephrine reuptake inhibitors (SNRIs), these drugs don’t work quite as well as tricyclic antidepressants, but they also don’t produce as many side effects.

Selective serotonin reuptake inhibitors (SSRIs) such as paroxetine (Paxil) and fluoxetine (Prozac) don’t appear to help relieve pain on their own. However, fluoxetine appears to boost the painkilling effects of some tricyclic antidepressants.