Pain
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Randomized Controlled Trial Comparative Study
Iontophoretic administration of S(+)-ketamine in patients with intractable central pain: a placebo-controlled trial.
The efficacy of 50 and 75 mg S(+)-ketamine administered daily by an iontophoresis-assisted transdermal drug delivery system was tested against placebo in a randomized, double-blind design in 33 patients with central neuropathic pain. At baseline and 1 week after the start of treatment subjects were evaluated with standard measures of efficacy: pain intensity measured by visual analog scale (VAS), health status (Pain Disability Index and EQ-5D) and quality of life (SF-36). Safety assessment included incidence and intensity of adverse events. ⋯ Iontophoretic administration of S(+)-ketamine was well tolerated with a low incidence of adverse events (mild and transient in nature, resolving spontaneously). Iontophoretic administration of S(+)-ketamine was not more effective than placebo treatment in reducing pain scores in patients with severe central neuropathic pain. However, iontophoretic administration of 75 mg S(+)-ketamine improved the health status and the quality of life in these patients.
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Comparative Study
Heart rate mediation of sex differences in pain tolerance in children.
Despite evidence supporting the existence of important sex-related differences in pain, the mechanisms underpinning such differences are not well understood. The aim of this study is to examine the relationship between sex and pubertal differences in autonomic arousal and pain tolerance to laboratory pain stimuli in healthy children. We tested the following specific hypotheses: (1) females would have greater autonomic arousal and less pain tolerance than males, and (2) this sex difference in pain tolerance would be mediated by autonomic arousal. ⋯ There were also significant effects for puberty, but these did not vary by sex. Overall, early pubertal children had greater pre-trial HR and less pain tolerance than those in late puberty for both cutaneous pressure and thermal pain across sex. These results suggest that autonomic arousal may be a mediator of sex-related differences in pain responses in children.
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Comparative Study
A prospective study of acceptance of pain and patient functioning with chronic pain.
Acceptance of chronic pain is emerging as an important concept in understanding ways that chronic pain sufferers can remain engaged with valued aspects of life. Recent studies have relied heavily on cross-sectional investigations at a single time point. The present study sought to prospectively investigate relations between acceptance of chronic pain and patient functioning. ⋯ Those patients who reported greater acceptance at Time 1 reported better emotional, social, and physical functioning, less medication consumption, and better work status at Time 2. These data suggest that willingness to have pain, and to engage in activity regardless of pain, can lead to healthy functioning for patients with chronic pain. Treatment outcome and process studies may demonstrate the potential for acceptance-based clinical methods for chronic pain management.
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Comparative Study
A human experimental capsaicin model for trigeminal sensitization. Gender-specific differences.
Migraine is much more common in women (18%) than in men (6%). Menstrual migraine in female migraineurs also varies from 7 to 19%. The main goals of the present study were (1) to investigate gender specific differences in an experimental capsaicin model of trigeminal sensitization (a proposed mechanism of migraine) and (2) to explore the influence of menstrual cycle phases. ⋯ A significant difference was found in the capsaicin-evoked pain distribution with a greater response in menstrual phase compared to the luteal phase (P<0.01) and men (P<0.0001). Capsaicin induced trigeminal sensitization and evoked gender specific sensory and vaso-motor responses, with menstruating females generally showing the strongest manifestations. The model may be further applied to explore mechanisms of human trigeminal sensitization.
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Some abdominal pain syndromes are characterized by persistent pain without demonstrable pathology. Many of them are prevalent in women and it is known that sex hormones are associated with differences in pain perception between males and females. To model a process of functional abdominal pain in females we studied the time course and estrogen dependency of a hyperalgesic state induced by ovariectomy in adult mice. ⋯ In another series of experiments a slow release pellet containing 17beta-estradiol was implanted in half of the OVX mice and a similar pellet without the hormone in the other half. Hormone replacement prevented the development of hyperalgesia in OVX animals but did not stop the involution of the internal reproductive organs. We conclude that OVX in mice provides a useful model for a hormonally dependent hyperalgesic state resembling functional pain.