Postgraduate medical journal
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The mechanisms of the antinociceptive action of flupirtine, a novel non-opioid analgesic, were investigated in animals. It was found that this effect could be abolished by pre-treatment with reserpine. Furthermore, it could be dose-dependently antagonized by yohimbine and changes in the EEG of the rat observed after administration of flupirtine were closely related to those obtained after giving clonidine. On these pharmacological results, it is likely that the antinociceptive activity of flupirtine is due to activation of descending noradrenergic pathways.
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Comparative Study
Comparative physical dependence studies in rats with flupirtine and opiate receptor stimulating analgesics.
In physical dependence studies in rats the principle criterion was loss of body weight after withdrawal of the dependence producing drug. Other typical signs of withdrawal were also observed. In contrast to buprenorphine, codeine and tramadol, flupirtine caused no decrease in body weight and no other withdrawal symptoms. Flupirtine does not produce opiate type physical dependence.
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In order to investigate the efficacy and safety of long-term treatment with flupirtine in patients with chronic pain, in particular arthrosis and arthritis, a study was planned which, when completed, will encompass the treatment of 200 patients over a 12-month period. The present paper is a preliminary report of this ongoing study. The report deals with 104 patients: 55 of whom completed the 12-month treatment period and a 2-week follow-up phase, during which flupirtine was replaced by placebo in order to be able to detect drug-withdrawal effects. ⋯ If the withdrawal phenomena had corresponded to the flupirtine's terminal half-life, then the symptoms ought to have been present mainly in the first few days. There was a slight trend for lowering systolic blood pressure but no changes in diastolic blood pressure or heart rate, nor changes in the ECG or laboratory analysis that could be related to flupirtine. These preliminary data suggest that flupirtine is safe when given for a period of one year.
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The antinociceptive activity of flupirtine was measured in various test procedures predictive of analgesic activity. In the electrostimulated pain test in mice the oral ED50 for flupirtine was 25.7 mg/kg p.o. Thus, flupirtine was approximately 31.7 times more potent than paracetamol (ED50: 814 mg/kg p.o.) and as potent as pentazocine (ED50: 38.5 mg/kg p.o.). ⋯ Whereas buprenorphine and tramadol showed a striking similarity in the pharmaco-electroencephalogram recorded from different parts of the brain (frontal cortex, thalamus, striatum and the mesencephalic reticular formation) of the freely moving rat, flupirtine was clearly different in action. It produced dose dependent increases in nearly all frequency bands but its effects were different from those of the minor tranquillizer diazepam and the anticonvulsant phenobarbitone. These findings show that the central antinociceptive activity of flupirtine is not based on an opiate mechanism and is not comparable with that of diazepam and phenobarbitone.
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Acute alcoholic pancreatitis was undiagnosed in a patient with anorexia nervosa who subsequently developed pancreatic ascites and oedema, wrongly attributed to protein malnutrition alone. She became hyperphagic in an attempt to reverse the malnutrition and hence the abdominal swelling, indicating that the goal of attaining a thin shape was the major determinant of the eating disorder in this patient. Measurement of ascitic fluid amylase concentration should be carried out in all patients with unexplained ascites.