Pain
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparative study of the efficacy and pharmacokinetics of oral methadone and morphine in the treatment of severe pain in patients with cancer.
Eighteen patients suffering from cancer were entered into a study of the pharmacokinetics and efficacy of methadone and morphine in pain control. All patients had both clinical and radiological evidence of metastatic spread of their cancer and there were no significant differences in age, weight and sites of the primary cancer between the methadone (n = 9) and morphine (n = 9) groups. Blood opioid concentration, visual analogue pain scores (VAPS) and end-tidal percent carbon dioxide were measured before and after both an intravenous and oral dose of either methadone or morphine. ⋯ The combined effects of low and variable oral bioavailability for morphine may result in sub-therapeutic doses being administered as practitioners may be inhibited by the size of the effective oral morphine dose and may be confused by the variability in this dose compared to intramuscular doses. The initial oral dose of morphine varied from 15 mg 4 hourly to 150 mg 3 hourly, while the initial dose for methadone varied from 15 mg on alternate nights to 20 mg twice daily. There was no rapid escalation of daily opioid dose for either methadone or morphine when adequate pain control was provided rapidly at the start of treatment by the technique described in this study.
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We investigated 8 healthy male volunteers, evaluating RII and RIII thresholds every 6 h starting from noon, for a 24-h period. Both reflex responses exhibited a circadian rhythmicity: the lowest values were found in the early morning (9.1 +/- 3.0 and 13.1 +/- 4.4 mA, respectively), while the highest values were observed at midnight (13.1 +/- 3.5 and 18.5 +/- 5.3 mA). ⋯ No correlation was observed between circadian changes of beta-EP and RIII threshold. Other factors are likely to be involved in the circadian variation of nociceptive flexion reflex in man.
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A hand-held pressure algometer with a pressure sensitive strain gauge at the tip was used to measure the pressure-pain threshold (PPT) in the temporal region of healthy volunteers. Various sizes of circular tips and various application rates were tested before selecting an area of 0.5 cm2 and a constant application rate of 0.68 N X sec-1 for future use. A highly significant correlation was found between PPT values obtained from the two sides (of the head) (P less than 0.001) and between PPT values obtained with a 3-week interval (P less than 0.001). ⋯ Subcutaneous lignocaine significantly elevated PPT compared to placebo. Due to the high inter-individual variation, determinations of PPT for group comparisons should include rather large population samples, whereas in paired studies, the intra-individual variation allows the investigation of much smaller groups (10-20 subjects). It is our experience that the pressure algometer is easy to operate in the hands of a skilled laboratory assistant.