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  • 1
    ISSN: 1432-2072
    Keywords: Opioid ; Drug discrimination ; Analgesia ; Fentanyl ; Rhesus monkey ; Competitive antagonism ; Respiratory function ; Self administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The recent synthesis of fentanyl derivatives, some of which appear to have novel profiles of pharmacological effects, has provided compelling evidence that μ opioid efficacy might be altered systematically by modifications in the parent compound fentanyl. In the present study a new 4-(heteroanilido)-piperidine, compound 28, was studied for its effects in rhesus monkeys. In self-administration studies compound 28 maintained rates of lever pressing similar to those maintained by alfentanil; the reinforcing effects of compound 28 were attenuated by the opioid antagonist quadazocine. In drug discrimination studies compound 28 did not substitute for the κ agonist ethylketocyclazocine and did substitute for the μ agonist alfentanil. In morphine-treated subjects discriminating between saline and naltrexone, compound 28 did not substitute for naltrexone; however, in morphine-abstinent subjects compound 28 reversed naltrexone lever responding. Moreover, this discriminative stimulus effect in morphine-abstinent subjects was antagonized by naltrexone and by quadazocine in a manner consistent with μ receptor mediation. Compound 28 also was an effective analgesic in a warm-water, tail-withdrawal procedure and it decreased markedly respiratory function. The analgesic effects as well as the respiratory depressant effects of compound 28 were antagonized by quadazocine. Together, these results show compound 28 to be a potent, efficacious μ agonist of similar potency to alfentanil. Large differences in apparent efficacy at μ receptors between compound 28 and another compound in this series (mirfentanil), clearly demonstrate that, within this chemical family, small chemical changes can confer significant differences in pharmacologic effect.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Key words Tolerance ; Cross-tolerance ; Dependence ; Mirfentanil ; Opioid ; Non-opioid ; Morphine ; Fentanyl ; OHM3463 ; OHM3295
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Mirfentanil is a fentanyl derivative with non-opioid actions, including non-opioid antinociceptive effects in rhesus monkeys. The current study examined the rate-altering effects of mirfentanil and several other compounds in pigeons to assess: 1) the opioid and non-opioid actions of acutely-administered fentanyl derivatives; and 2) the development of cross-tolerance between each of these compounds and morphine. Seven pigeons responded under a fixed-ratio 20 (FR20) schedule of food delivery. In untreated pigeons, fentanyl, morphine, naltrexone, ketamine and three fentanyl derivatives (mirfentanil, OHM3463 and OHM3295) decreased rates of key pecking in a dose-related manner. Naltrexone (0.1–1.0 mg/kg) attenuated the effects of OHM3463 and not mirfentanil or OHM3295, suggesting non-opioid mediation of the rate-decreasing effects for the latter two fentanyl derivatives. Subjects were treated daily with morphine for 9 weeks, up to a dose of 100 mg/kg per day, during which time the dose-effect curves for morphine, fentanyl and OHM3463 shifted rightward 6-, 10- and 2-fold, respectively, indicating the development of tolerance to morphine and cross-tolerance to fentanyl and OHM3463. Dose-effect curves for ketamine, OHM3295 and mirfentanil were not shifted to the right during morphine treatment, and the dose-effect curve for naltrexone was shifted leftward 180-fold. To the extent that rate-decreasing effects are predictive of antinociceptive effects, these data suggest that some fentanyl derivatives might be useful therapeutics under conditions where tolerance develops to morphine-like opioids.
    Type of Medium: Electronic Resource
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