Volume 2, Issue 1

Introduction and aim Pain sensitivity has been linked to the melanocortin-1 receptor (MC1R) gene. A mutation in MC1R can result in pale skin and red hair in humans and may modulate pain responses in general. Human studies have shown that women with non-functional MC1R’s were sensitive to experimental induced cold and heat pain. A study demonstrated that females with red hair required higher dose of anesthesia than females with dark hair to experience analgesia to electrical stimulation. Moreover, women expressing non-functional MC1Rs display greater analgesia from opioid analgesia. If redheads in general respond differently to pain and analgesics, this is of clinical importance. The aim of this study was therefore to investigate pain sensitivity and experimentally induced sensitisation in red haired females. Method Twenty healthy females with pale skin and red hair (mean age 32 years, range 20–55) and 20 healthy females with blond/dark hair (mean age 31 years, range 20–51) participated in this study. The pain tolerance thresholds to heat and pressure stimulation were determined. Hyperalgesia was induced experimentally by applying 0.075% topical capsaicin cream for 30 min. The secondary pin-prick hyperalgesic area was estimated with a calibrated filament (von Frey hair, 15 g) and the area of allodynia by a soft brush. This was done 0, 30, 60, and 90 min after cream removal. Results Neither heat nor pressure pain tolerance thresholds were changed in the two groups. The secondary pin-prick hyperalgesic areas were significantly smaller for red haired females than blond/dark haired females ( P = 0.014). There were no significant differences in the allodynic areas. Discussion As the secondary hyperalgesic response evoked by topical capsaicin is a central phenomenon, the observed smaller pin-prick hyperalgesic area in the red haired females could indicate a central role of MCRs in development or maintenance of hyperalgesia. Central involvement of MC1Rs or dysfunction of peripheral MC1Rs activating central MC4Rs has been suggested to influence pain sensitivity. The difference observed between red haired and non-red haired females may have implications for pain management regimens as compounds interacting with sensitisation such as NMDA-antagonists or alpha-2-delta-ligands may exert different types of action in people with MC1R mutation. Conclusion The present study showed that red haired females were less sensitive to topical capsaicin induced pin-prick hyperalgesia compared with blond/dark haired females. Implications The smaller hyperalgesic area in redheads could be a manifestation of central anti-hyperalgesic involvement of MCRs and could have an influence on the treatment of pain as well as in studies investigating anti-hyperalgesic drugs.

Background and aim Pain due to a usually non-painful mechanical stimulus, mechanical allodynia, is an oppressive symptom in subgroups of patients with neuropathic pain. Dynamic mechanical allodynia (DMA) is evoked by a normally innocuous light moving mechanical stimulus on the skin and static mechanical allodynia (SMA) by a sustained, normally innocuous pressure against the skin. DMA is claimed to be mediated by myelinated fibres and SMA by C-fibres. Also A-delta fibres have been implicated in the static subtype. A low intensity vertically applied stimulus of 1 second (s) is expected to activate predominantly rapidly adapting A-beta mechanoreceptors thus recruiting the same peripheral substrate as a horizontally moving brush on top of the skin. In patients with SMA we assumed an activation of Cbut also A-delta fibres from a static 10 s von Frey filament stimulus. The aim was to investigate if DMA and SMA could be assessed at perception threshold level using short or longer lasting usually non-painful von Frey filament prodding of the neuropathic skin. Patients and methods Eighteen patients with painful unilateral partial peripheral traumatic nerve injury suffering from SMA ( n = 9) and/or DMA ( n = 18) in a limb were studied. A compression/ischemia-induced (differential) nerve block in conjunction with repeated quantitative sensory testing of A-delta and C-fibre function using cold and warm stimuli was used to assess which nerve fibre population that contributes to pain at perception threshold level using 1 s (vF1) and 10 s (vF10) von Frey filament stimulation of the skin. Results The main outcome was the finding that elevation of vF1 and vF10 occurred simultaneously and significantly prior to an increase in the perception level to cold or warmth during the continuous nerve block. Single patients demonstrated a slight decrease in cold perception levels at the time of elevation of vF1 or vF10 and a possible contribution to mechanical allodynia from A-delta-fibres can therefore not completely be ruled out although the recorded alterations were minor. None of the patients reported an elevation of the perception level to warmth at the time of elevation of vF1 or vF10 excluding contribution from C-fibres. Further, only patients with clinically established SMA ( n = 9) reported continuous pain to a sustained 10 s von Frey filament stimulation (vF10). Patients with only DMA ( n = 9) reported pain merely for the initial 1–3 s of the total stimulus duration of 10 s and for a few seconds after the filament was lifted from the skin. Conclusions These findings support the role of A-beta fibres as peripheral mediators of both vF1 and vF10 although different receptor organs may be involved, i.e., rapidly (RA) and slowly (SA-I) adapting mechanoreceptors. Implications Techniques to quantify the different allodynias at perception threshold level deserve further attention as possible adjuncts to suprathreshold stimuli in intervention studies aimed at modifying these stimulus-evoked phenomena.

Background and aims Medical abortion is often performed at outpatient clinics or gynaecological wards. Yet, some women may stay at home during medical abortion. Pain has been reported to be one of the main side effects of the procedure. Methods We studied whether perceived abortion pain was related to the subjectively evaluated ability to stay at home during medical abortion. The size of the study group was 29 women. We also studied how well these women remembered the intensity and unpleasantness of the abortion pain in a control visit performed 3–6 weeks after abortion. Results Especially, the unpleasantness associated with the pain during abortion was an important predictor when women evaluated their ability to stay at home during medical abortion. In those women who might have been able to stay at home in their own view, midwives looking after these women at the outpatient clinic estimated the pain intensity and unpleasantness also about 50% lower than in those who were not able to stay home in their own view. There were no significant differences in intensity, unpleasantness in hindsight of menstruation pain, or the area of this pain in the pain drawings in those women who considered that they might have stayed at home during medical abortion when compared with those who did not. No difference was found in age, gestational age, magnitude of previous pregnancies, miscarriages, vaginal deliveries, induced abortions, Beck’s Depression Index (BDI), Beck’s Anxiety Index (BAI) or AUDIT scores between those who could have stayed at home or those who would not have been able to stay at home during abortion. Components of abortion pain decreased significantly during the second post-abortion day. The more deliveries the subject had experienced the less pain she had during abortion. Multiparous women reported less than a fourth of the pain magnitude of the nulliparous women during abortion. Parity explained both intensity and unpleasantness of abortion pain better than the expected ability to stay at home. The remembrance of the intensity or unpleasantness of abortion pain correlated with actual pain reported at the time of abortion. However, this remembrance did not correlate with the ability to stay at home during the medical abortion. Conclusions The unpleasantness of pain during and immediately after abortion was recalled, not as a measure of the pain itself, but as a deciding factor in their judgement of whether or not they would be able to undergo medical abortion at home. Abortion pain is an important factor in enhancing home-based management of medical abortions. Medical staff may be able to detect those women who do not cope at home during the process by observing the intensity of pain. Therefore, proper treatment of pain might reduce the need for hospital-based medical abortions. Implications These patients need better care and guidelines for the care of women undergoing medical abortions should include clear recommendations for analgesic treatments, at the least adequate doses of nonopioid analgesics such as paracetamol in combination with NSAIDs like ibuprofen or diclofenac.

Background and purpose Botulinum toxin type A (BoNT-A) has antinociceptive and muscle-relaxant properties. The objectives of this study were to investigate the efficacy and safety of a single BoNT-A (Dysport ® ) treatment in myofascial back pain. Methods In this randomized, open-label, multicenter study, adults with myofascial lower back pain received Dysport ® injections at four trigger points (60,80 or 120 units per injection point). Patients were followed for 12 weeks. The a priori primary endpoint was a pooled evaluation, at Week 6, of seven measures of efficacy, including pain intensity (patient diary), modified Pain Disability Index (PDI) score, use of interfering concomitant analgesics, and patient-rated global efficacy. Optional assessments of pressure thresholds and tissue compliance were conducted. Safety was also assessed. Results A total of 202 patients were randomized to treatment and 189 patients received a low ( n = 57), medium ( n = 57), or high ( n = 75) total dose of Dysport ® at 34 centers in Germany between October 2002 and October 2003. All treated patients were included in the safety population; 8 patients were excluded from the intention-to-treat population. Patients had moderate to severe pain at baseline. At baseline, 120 patients were receiving concomitant analgesic therapy; 6.7%, 74.2% and 19.2% were considered to cause mild, moderate and severe interference with pain measurements, respectively. There was no difference between doses for the a priori combined primary endpoint. Patient-reported pain intensity scores at rest and on movement decreased significantly after treatment for all groups combined ( p < 0.0001 at all visits). At Week 6, reductions in pain intensity at rest were 29%, 19% and 26% for the low-, medium- and high-dose groups, respectively; reductions in pain intensity on movement were 27%, 18% and 26%, respectively. Overall, patients who reported pain intensity reductions at Week 6 were evident within 3 weeks of treatment and were maintained for the 12 weeks of the study. In the total population, significant decreases in mean PDI sum scores from baseline were observed from Week 3 and were maintained through to the end of treatment (Week 12); no differences between the dose groups were observed. Pressure thresholds and tissue compliance also increased during the study. Adverse events were generally as expected for BoNT-A; the majority were mild or moderate in severity. Conclusions Dysport ® treatment was associated with reductions in myofascial back pain and was well tolerated. Nodose-response relationship was observed; treatment with Dysport ® using a four-trigger-point injection protocol at 60 units per trigger point was associated with a clinically relevant and statistically significant improvement in pain and pain-related disability; there was no additional benefit from the higher doses. Implications Our findings are limited by the lack of a control group and further research is warranted to confirm the value of Dysport ® for the treatment of myofascial back pain and confirm the optimum dosing in this indication.

Purpose To examine and compare dispensing of prescribed analgesics between young people with parents from countries with a Muslim majority and those with parents born in Norway. Methods Our study-population constituted 11,542 adolescents from the Norwegian Youth Health Surveys conducted in 2000–2003. Users and non-users of prescribed analgesics at baseline were analysed separately. Self-reported information on their parents’ birth country was used to classify them into one of the three predefined groups: Norway, countries with a Muslim majority or others. To study and compare dispensing of prescribed analgesics, data from the youth surveys were linked to the Norwegian Prescription Database (NorPD) 2004–2007. Dispensed analgesics studied were antiinflammatory and antirheumatic products (non-steroid), opioids and other analgesics and antipyretics. Results Among non-users of prescribed analgesics at baseline, 34% of all males with parents born in Norway received prescribed analgesics at least once during 2004–2007, compared to 36% in the group with parents from countries with a Muslim majority. The proportions of females receiving prescribed analgesics were about 44% in both of the two previously mentioned groups. Among users of prescribed analgesics at baseline, the proportion of individuals who were dispensed prescribed analgesics in 2004–2007 was generally higher than for those that were non-users at baseline. Both males and females with parents from countries with a Muslim majority reported more pain compared to those with parents born in Norway. No statistical differences were detected between participants with parents from countries with a Muslim majority compared to those with parents born in Norway in terms of prescribed analgesics dispensed or total amount of analgesics dispensed in 2004–2007. For the dispensing of all analgesics in 2004–2007 the adjusted OR for having parents from countries with a Muslim majority compared to parents born in Norway was 1.02 (0.87–1.21) among non-users of prescribed analgesics at baseline and 0.82 (0.57–1.16) among users. Conclusions There were no differences in the dispensing of prescribed analgesics between young people with parents born in countries with a Muslim majority and those with parents born in Norway. Nor did the amount of prescribed analgesics differ between these groups.