Duloxetine is FDA-approved for the treatment of depression as well as for treatment of DPNP. Thus, it can provide the antidepressant benefits of the TCAs but with a much more benign side-effect profile. Unlike the TCAs, it is not a very sedating drug; therefore, if insomnia is a problem, an additional sleep medication may be required. It should be noted that the reviews indicated that venlafaxine (Effexor), a second-line drug for DPNP, should be considered if there is limited response to the first-line agents; venlafaxine shares the same advantages as duloxetine(Drug information on duloxetine). TCAs, duloxetine, and venlafaxine are all primarily serotonin-norepinephrine reuptake inhibitors (SNRIs). Tramadol(Drug information on tramadol) (Ultram)--which the reviews also considered a second-line medication for DPNP--shares the benefits of these drugs, and although it also contains an opioid, its analgesic effect appears to be predominantly associated with its actions as an SNRI.
Pregabalin is approved as an analgesic for both DPNP and PHN and as an anticonvulsant for seizures related to epilepsy. Many anticonvulsants have been found to be effective analgesics for neuropathic pain, but side effects have often limited their use. Pregabalin(Drug information on pregabalin) appears to be better tolerated than its predecessors. Its major side effects are dizziness and sedation in patients prone to falls or who have problems with balance, so this treatment should be prescribed with caution. Pregabalin does appear to be a less sedating medication than gabapentin(Drug information on gabapentin) (Gabarone), another anticonvulsant that is approved for use in PHN and is considered by the reviews to be a second-tier drug for treating DPNP.
Whether controlled-release oxycodone(Drug information on oxycodone) actually provides more analgesia for DPNP than the other long-acting opioids is open to question. There are many studies supporting its use in DPNP, which may be because of the fact that it is one of the newer opioid preparations. Certainly if the antidepressants and anticonvulsants described do not provide relief, its use should be considered. The use of any opioid is associated with certain risks--most notably abuse, physical and psychological dependence on the drug, and the potential for exacerbating depression.
Although combinations of medications are often used in clinical practice, there are few formal studies of them. If a combination is considered, medications with different mechanisms of action should be tried.
With regard to nonpharmacologic treatments, Argoff and coworkers5 noted that although there are limited studies on acupuncture, there is evidence to support its use, especially in light of the limited risk of side effects associated with it.
Dr King is clinical professor of psychiatry at the New York University School of Medicine, New York.