Denver - Selecting the appropriate drug category is important to effectively manage itch, Sarina Elmariah, M.D., Ph.D., told attendees at the 72nd Annual Meeting of the American Academy of Dermatology.
"One of the most important factors in managing itch is targeting the right itch," says Dr. Elmariah, instructor in dermatology at Massachusetts General Hospital, Boston.
Different drugs are thought to target pruritoceptive, neuropathic, neurogenic and psychogenic itch. But recently, "I've changed my perspective regarding how these types of itch can impact my patients, because based on my research there's a blurring of these lines."
For example, she says that pruritoceptive itch, which stems primarily from inflammation in the skin, has a neurological component as well.
With that in mind, she outlined the utility of the following drug categories:
- Anticonvulsants: "These are aimed at stabilizing the nerves. They increase the activity of gamma-aminobutyric acid in the CNS (central nervous system), and they decrease the activity of excitatory nerve transmitters." As such, she says, gabapentin has been used extensively off-label for neuropathic pain and itch. "And there's been efficacy reported for the treatment of neuropathic, post-burn, uremic, cholestatic and postherpetic itch." Gabepentin and pregabalin work equally well, Dr. Elmariah adds, though gabapentin works more slowly.
- Antidepressants: In this category, she says paroxetine tends to work best. In an open-label study involving 72 patients with diverse itch etiologies, researchers found that paroxetine (20 mg to 40 mg daily) or fluvoxamine (50 mg to 150 mg daily) decreased itch in 68 percent of patients overall at approximately five weeks (Ständer S, Böckenholt B, Schürmeyer-Horst F, et al. Acta Derm Venereol. 2009;89(1):45-51).
- Opioids: In this category, which Dr. Elmariah says she uses increasingly, "Naltrexone is tolerated very well. If patients are going to get side effects, they usually happen late," at around four weeks. "Side effects can include nausea, abdominal cramping, fatigue, blurred vision and, very rarely, hepatitis." Opioids also can precipitate withdrawal symptoms in opioid-dependent patients, she notes.
- Cannabinoids: Dr. Elmariah says her inspiration to prescribe this category stems from the case of a 15-year-old boy with intractable atopic dermatitis (AD) who confessed - after his mother left the exam room - to smoking marijuana. "Over the last 1.5 years, I have prescribed cannabinoids and dronabinol in almost 30 patients with AD, idiopathic itch and even drug reactions. In properly selected cases, cannabinoids work very well. I'm quite a fan."