TCAs used to treat comorbid depression and pain conditions include amitriptyline, nortriptyline, imipramine, and desipramine.14 TCAs are cost-effective medications for managing neuropathy and headache; however, the dosages used for pain tend to be lower than those typically used for depression.
TCAs are not commonly prescribed for depression because of their side-effect profile and poor tolerability. TCAs are contraindicated in patients with cardiac conduction abnormalities, epilepsy, and narrow-angle glaucoma. Common adverse effects include dry mouth, sweating, dizziness, orthostatic hypotension, sedation, weight gain, urinary retention, and constipation. These adverse effects limit their use and have organizations, such as the American Geriatric Society, to caution against their use in geriatric patients.
SNRIs that have been studied for pain disorders include venlafaxine, duloxetine, and milnacipran.2 Of note, milnacipran is not FDA-approved for MDD, but its L-enantiomer, levomilnacipran, is. Unlike duloxetine and venlafaxine, both milnacipran and levomilnacipran are not available as a generic formulation, therefore they have a higher patient cost. The SNRI dosages used for pain management tend to be similar to those used for MDD, indicating that the target dosage may be effective for both depressive and pain symptoms.
Selective serotonin reuptake inhibitors (SSRIs). Compared with data available supporting the use of TCAs and SNRIs for pain management, the data for SSRI are sparse. Studies have evaluated fluoxetine, paroxetine, and citalopram for pain, with the most promising data supporting fluoxetine.2 Fluoxetine, 10 to 80 mg/d, has been evaluated in randomized, placebo-controlled trials for pain conditions, including fibromyalgia (n = 3), painful diabetic neuropathy (n = 1), and facial pain (n = 1). Fluoxetine was more effective than placebo at controlling pain in 2 fibromyalgia studies (dosage range, 10 to 80 mg/d) and 1 facial pain study (dosage, 20 mg/d).2
CASE CONTINUED
When evaluating potential treatment options, it is noted that Ms. C is prescribed sertraline, 200 mg/d, but has been taking a lower dosage. Ms. C states that she has been taking sertraline, 100 mg every morning, for months, and noticed some minor initial improvements in mood, but still has days when she don’t feel like doing anything. She fills out a depression rating scale classifying her current depression as moderately severe. Today she rates her pain as 7 out of 10. Suboptimal control of her depression may require a dosage increase; however, perhaps a change in therapy is warranted. It may be prudent to switch Ms. C to an SNRI, such as duloxetine, an agent that can address her depression and provide additional benefits of pain control.
Switching from a SSRI to duloxetine has been shown to be effective when targeting pain symptoms in patients with comorbid MDD. In addition, improvements in pain scores have been seen after a switch to duloxetine in patients with depression with nonresponse or partial response to a SSRI.15
Studies support the decision to change Ms. C’s medication from sertraline to duloxetine, despite an inadequate therapeutic trial of the SSRI.