Recent research suggests similarities in the etiologic and pathogenetic mechanisms of chronic pelvic pain syndrome and other pain syndromes.
Chicago-Recent research suggests similarities in the etiologic and pathogenetic mechanisms of chronic pelvic pain syndrome (CPPS) and other chronic pain syndromes, such as migraine and irritable bowel syndrome (IBS). The findings may lead to a new treatment approach for CPPS, researchers say.
Evidence is building from MRI studies of CPPS and research in IBS that visceral hypersensitivity and hyperalgesia in central pain syndromes may depend on the activity of the N-methyl-D-aspartate (NMDA) receptor. Blocking the NMDA receptor would, in theory, quell pain transmission. That theory formed the core of a study presented at the AUA annual meeting by Jordan Dimitrakov, MD, PhD, instructor in surgery (urology) at Harvard Medical School, Boston.
"To us, there are at least three possible mechanisms in which memantine can be beneficial in CPPS: modulation of glutamate toxicity in the central nervous system, modulation of dopamine transmission or dopaminergic neurotransmission, and modulation of serotonergic neurotransmission in the central nervous system," said Dr. Dimitrakov, who was previously on staff at the Medical University of Plovdiv, Bulgaria, which performed this study.
The primary outcome was pain relief at 6 months based on the NIH-Chronic Prostatitis Symptom Index (CPSI) pain domain scale; the secondary endpoint was patient-reported improvement in NIH-CPSI quality of life score, global response assessment, and voiding.
At 6 months, significant improvement in pain, quality of life, and global response assessment score was reported by 77% of men taking memantine compared with 16% of placebo recipients (p<.001). At 1 year, patients in the treatment group reported sustained improvement in pain and quality of life compared with the placebo group.
No between-group difference was seen on the voiding subscale of NIH-CPSI.
"That's not surprising, given the fact that most of the patients enrolled at baseline actually reported predominantly pain-related symptoms, rather than voiding symptoms," Dr. Dimitrakov noted.
Side effects of memantine were minimal; the most frequently reported were dizziness (7%), headache (5%), and tiredness (1%).
'Safe and effective'
"There are a couple of messages for the clinician," Dr. Dimitrakov said. "The main message is that we need to see a larger study in men with CPPS to evaluate this medication in more detail. The second is that in our hands, this medication appears safe and effective, with minimal side effects. Finally, this is a medication that actually works on a subset of patients. It would be unrealistic to think that a medication is going to be effective in all patients with CPPS."
Memantine's efficacy and safety are yet to be studied in women, although pilot data from a small, uncontrolled study show similar results. Dr. Dimitrakov and colleagues currently are following 30 women with painful bladder syndrome/interstitial cystitis who have been treated with the drug. He told Urology Times that results are expected toward the end of 2010.