The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Multicenter Study
Pregabalin for postherpetic neuralgia: placebo-controlled trial of fixed and flexible dosing regimens on allodynia and time to onset of pain relief.
Time to onset of pain relief and improvement in allodynia in 269 patients with postherpetic neuralgia was examined in a 4-week randomized trial comparing flexibly dosed pregabalin (150-600 mg/d), fixed-dose pregabalin (300 mg/d), and placebo. For each patient with clinically meaningful pain reduction (>or=30%) at end point, onset of pain relief was defined as the first study day on which a patient reported >or=1-point reduction in pain relative to baseline. Average dose achieved was 396 mg/d in the flexible-dose group compared with 295 mg/d in the fixed-dose group. Median pain relief onset times were 3.5 days (flexible-dose), 1.5 days (fixed-dose), and >4 weeks (placebo). Compared with placebo, significantly more patients in both pregabalin treatment groups achieved >or=30% and >or=50% pain reduction at end point. Almost 95% of patients had brush-evoked allodynia, with 68% having moderate to severe allodynia (>or=40/100 mm). At baseline, pain and allodynia were highly correlated. Independent of treatment assignment, improvement in pain and improvement in allodynia were significantly correlated. Allodynia could serve as a useful surrogate outcome measure in future studies. Pregabalin was significantly better than placebo in alleviating allodynia (flexible-dose reduction, 26 mm; fixed-dose, 21 mm; placebo, 12 mm). Discontinuation rates due to adverse events were more frequent in the fixed-dose group. ⋯ A flexible-dose regimen reduces discontinuations, facilitates higher final doses, and results in a slightly greater pain relief. Allodynia (touch-evoked pain) can be of disabling severity and is present in nearly all patients with postherpetic neuralgia. Allodynia severity is correlated with pain severity and improvement in allodynia is correlated with clinical response.
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Multicenter Study
Trends in use of opioids by noncancer pain type 2000-2005 among Arkansas Medicaid and HealthCore enrollees: results from the TROUP study.
Use of prescription opioids for noncancer pain has increased significantly in recent years, but it is not known if trends differ among the most common noncancer pain conditions. We examined trends in opioid prescribing for the years 2000 through 2005 for individuals with arthritis/joint pain, back pain, neck pain, and headaches by type and number of pain diagnoses, using data from claims records from 2 health insurers: HealthCore commercially insured members (N = 3,768,223) and Arkansas Medicaid (N = 127,866). Rates of headache, back pain, and neck pain diagnoses increased significantly in Arkansas Medicaid enrollees but more modestly among HealthCore enrollees. Rates of opioid use increased in both groups, with long-term use (>90 days' supply per year) increasing at twice the rate of any use. Rates of opioid use did not differ widely between noncancer pain conditions, but long-term opioid use rates doubled with each additional pain diagnosis. Mean days supply and cumulative yearly dose increased between 2000 and 2005 for all pain types and with increasing number of pain diagnoses, but dose per day supply remained relatively stable. The greatest increases in dose among all the pain conditions were seen in short-acting DEA Schedule II opioids. ⋯ This study demonstrates increased use of opioids, particularly long-term use, in noncancer pain over a 6-year period among those with multiple pain types. These results appear to reflect a general increase in use of prescription opioids for noncancer pain rather than a condition-specific change in prescribing practices.
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Patients often experience hard-to-treat neuropathic pain and other sensations after surgery; consequently, they could develop chronic pain conditions. The phantom limb phenomenon is a well-documented postoperative pain condition. However, phantom phenomena after mastectomies are less documented. The reviews report several views on the prevalence of breast phantoms and coexisting distress. Researchers observed that new methodological approaches might facilitate further research of these issues. This prospective, qualitative study used semistructured interviews to acquire knowledge of if and how phantom breast phenomena appear within the range of other postmastectomy symptoms and sensations. The study revealed that a phantom breast could be difficult to describe and position spatially. The phantom breast phenomenon varied from classic phantom extremity phenomenon and did not seem to cause much distress. However, it proved to be a phenomenon so unknown and different that there is urgent need for more knowledge. This study highlights the importance of further investigation regarding how information and communication related to a phantom breast might be developed. ⋯ The phantom breast is only one piece of a complicated puzzle. Because it was relatively unknown for the women in the study, it is important that analyses of this phenomenon, as a part of a postmastectomy syndrome, be conducted in a dialogue with the patients, by scientifically using qualitative methods.
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In this descriptive study of chronic pain in a community sample of 292 women who had separated from their abusive partners on average 20 months previously, more than one-third experienced high disability pain as measured by Von Korff's Chronic Pain Grade. Beyond the usual pain locations associated with abuse, 43.2% reported swollen/painful joints. More interference in daily life was attributed to joint pain than to back, head, stomach, pelvic or bowel pain. Women with high disability pain were more likely to have experienced child abuse, adult sexual assault, more severe spousal abuse, lifetime abuse-related injuries, symptoms of depression and post-traumatic stress disorder, lifetime suicide attempts, difficulty sleeping, and unemployment. High disability pain also was associated with visits to a family doctor and psychiatrist and use of medication in more than prescribed dosages. Less than 25% of women with high disability pain were taking opioids, or prescription nonsteroidal anti-inflammatory medications. Interestingly, high disability pain was not related to smoking, use of street drugs, potential for alcohol dependence, age, income, or education. The findings add to knowledge of severity and patterns of chronic pain in abused women and support the need for further multivariate analysis of the relationships among abuse experiences, mental health, and chronic pain severity to better inform decisions regarding diagnosis and treatment. ⋯ Understanding patterns of chronic pain in abuse survivors and their associations with abuse history, mental health symptoms, health service use, and medication is important for clinical assessment and intervention. Chronic pain persisted long after leaving abusive partners and extended beyond usual locations (back, headache, pelvic, gastrointestinal) to include swollen/painful joints.
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Trigeminal nerve damage often leads to chronic pain syndromes including trigeminal neuralgia, a severely debilitating chronic orofacial pain syndrome. Options for treatment of neuropathic pain are limited in effectiveness and new approaches based on a better understanding of the underlying pathologies are required. Partial ligation has been shown to effectively mimic many of the qualities of human neuropathic pain syndromes. We have devised a mouse model of trigeminal neuralgia using a partial infraorbital nerve ligation (pIONL) that induces persistent pain behaviors and morphological changes in the brainstem. We found that the pIONL effectively induced mechanical allodynia lasting for more than 3 weeks. Cell proliferation (bromodeoxyuridine), activation of astrocytes and microglia in the ipsilateral caudal medulla, and persistent satellite cell reaction in the ipsilateral ganglion were observed. Neurochemical markers calcitonin gene-related peptide, substance P were decreased in medullary dorsal horn ipsilateral to the injury side, whereas substance P receptor NK1 expression was increased after 8 days. Nerve injury marker ATF3 was markedly increased in ipsilateral trigeminal ganglion neurons at 8 days after pIONL. The data indicate that partial trigeminal injury in mice produces many persistent anatomical changes in neuropathic pain, as well as mechanical allodynia. ⋯ This study describes the development of a new mouse model of trigeminal neuropathic pain. Our goal is to devise better treatments of trigeminal pain, and this will be facilitated by characterization of the underlying cellular and molecular neuropathological mechanisms in genetically designed mice.