The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial Multicenter Study Comparative Study
Oxytrex minimizes physical dependence while providing effective analgesia: a randomized controlled trial in low back pain.
Physical dependence or withdrawal is an expected effect of prolonged opioid therapy. Oxytrex (oxycodone + ultralow-dose naltrexone) is an investigational drug shown here to minimize physical dependence while providing strong analgesia with twice-daily dosing. In this 719-patient, double-blind, placebo- and active-controlled Phase III clinical trial in chronic low back pain, patients were randomized to receive placebo, oxycodone qid, or oxytrex qid or bid. Each oxytrex tablet contains 1 microg naltrexone; oxytrex bid and qid treatments provide 2 and 4 microg naltrexone/day, respectively. Following a washout, patients with pain >or=5 on a 0-10 scale were dose-escalated weekly from 10 up to 80 mg/day until reaching adequate pain relief (
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The aim of the current study was to adapt the orofacial formalin pain model previously developed in rats for use in mice and to characterize as fully as possible the behavioral changes in this species. The effects of subcutaneous injection of different formalin concentrations (.5%, 1%, 2%, 4%, and 8%) were examined on the face-rubbing response. In mice, formalin injection into the upper lip induced sustained face-rubbing episodes with vigorous face-wash strokes directed to the perinasal area. A positive linear relationship between formalin concentration and amplitude of the rubbing activity was observed during the first and second phase of the test with concentration up to 4%. With the highest concentration used (8%), the amplitude of both phases had plateaued. Systemic administration of morphine and paracetamol induced a dose-dependent inhibition of the rubbing behavior during the second phase. Although both paracetamol and morphine inhibited the first phase, a dose-dependent inhibition was found only for morphine. The ED50 value (95% confidence interval) for suppressing the rubbing response during the first phase was 2.45 mg/kg (1.90-3.08 mg/kg) for morphine. The ED50 values for suppressing the rubbing response during the second phase were 3.52 mg/kg (2.85-4.63 mg/kg) for morphine and 100.66 mg/kg (77.98-139.05 mg/kg) for paracetamol. Heterosegmental nociceptive stimulation evoked by subcutaneous injection of capsaicin into the back of the animal 10 min before the formalin test produced a dose-dependent inhibition of the second phase of the rubbing response. The ED50 values for suppressing the rubbing response during the first and second phases were 9.04 microg (1.36-65.13 microg) and 0.92 microg (0.28-2.99 microg), respectively. In conclusion, the mouse orofacial formalin test appears to be a reliable model for studying the behavioral encoding of the intensity of nociceptive orofacial stimulation and the counter-irritation phenomenon and for testing analgesic drugs. ⋯ To further exploit the new opportunities of investigating nociceptive processing at the molecular level with the transgenic "knockout" approach, we require suitable behavioral models in mice. The presented mouse orofacial formalin test appears to be a reliable model for studying the behavioral encoding of the intensity of nociceptive stimulation and the counter-irritation phenomenon and for testing analgesic drugs.
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There is substantial evidence that men and women differ in their perception and experience of pain. However, research on sex differences in pain has mainly relied on self-report ratings, whereas little is known about sex differences in facial expression of pain. The aim of the present study was to investigate: 1) whether men and women differ in their facial expressiveness of pain; and 2) whether sex modulates the relationship between self-report and facial pain responses when tonic experimental pain is applied. Forty young and pain-free individuals (male n = 20, female n = 20) were investigated for their subjective and facial responses to tonic heat stimulation at both painful and nonpainful levels. Tonic heat stimulation was tailored to the individual pain threshold. Self-report was assessed via visual analog scales. Facial expression was objectively examined using the Facial Action Coding System. Correlation analyses for the relationship between self-report and facial expression of pain were conducted. Men and women differed neither in self-report ratings nor in facial responses during tonic heat stimulation. However, sex had a considerable impact on the relationship between these variables. Whereas no significant correlations at all were found for men, we obtained several significant correlations in woman. For that reason, future studies investigating the relationship between self-report and nonverbal pain behaviors should consider sex as an important modulating factor. ⋯ The findings of the present study suggest that facial responses to pain can be used as estimates of the intensity of subjective pain in women better than in men.
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Comparative Study
Disability determination: validity with occupational low back pain.
Disability determination for occupational low back pain challenges indemnification systems because spinal pathoanatomy is weakly related to pain intensity and functional capacity, making judgments of disability vulnerable to such confounding factors as sociodemographic variables (eg, race, socioeconomic status). To assess the contribution of impairment, race, and socioeconomic status to disability ratings and post settlement functional status, the current study investigated 580 African American and 892 white workers' compensation claimants with occupational low back pain who were surveyed an average of 21 months after claim settlement. Results indicated that diagnosis, surgery, and medical costs (indicators of impairment) were associated with disability ratings at the time of case settlement. African American race was negatively associated with disability ratings and also with diagnosis/surgery and medical costs. Disability ratings, however, correlated only weakly with post settlement status at 21-month follow-up. The association between race and disability ratings suggests that inequities operate in disability determination. Furthermore, the relative lack of association between disability ratings and postsettlement status raises questions about the validity of disability determination for workers' compensation claimants with low back pain. ⋯ Results demonstrated apparent racial/ethnic disparities in treatment and little association between disability ratings and post settlement status. Together, these results raise questions about social justice in the management of occupational back pain, as well as the validity of associated disability determination processes.
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Comparative Study Clinical Trial
Impact of outside regulatory investigation on opiate administration in the emergency department.
This study was conducted to determine whether outside regulatory investigation related to opiate prescription diversion changes the prescribing frequency of opiates in an emergency department (ED). The presence of ED administration of opiates and prescriptions for opiates on discharge were compared across a baseline period 90 days before arrest of a physician for opiate diversion, a period immediately surrounding the arrest, and a follow-up period 90 days later. At no time was there investigation of excessive opiate prescribing for patients in the ED. The likelihood of receiving opiate analgesia either in the ED or on discharge was not significantly different for patients reporting mild pain or severe pain across all three periods. Patients with moderate pain (self-reported pain scores of 4 to 6 out of 10) were less likely to receive opiates in the ED immediately after the arrest compared with the baseline period (likelihood ratio, 0.4; confidence interval, 0.2 to 0.7). Patients with moderate pain were also less likely to receive prescriptions for opiates on discharge from the ED immediately after the arrest (likelihood ratio, 0.5; confidence interval, 0.3 to 0.9). These effects had diminished by 90 days. ⋯ This study indicates that factors outside of the provider-patient relationship influence the likelihood of receiving opiates during an ED visit. Awareness of this phenomenon might serve to reduce oligoanalgesia.