Articles: narcotic-antagonists.
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Case Reports
Relief by naloxone of morphine-induced spasm of the sphincter of Oddi in a post-cholecystectomy patient.
Spasm of the sphincter of Oddi is a well-recognized effect of the narcotic class of drugs. Although it is usually clinically silent, such spasm occasionally causes debilitating pain that may be mistaken for more serious disorders. We present the case of a patient who had undergone cholecystectomy previously, but in whom morphine given in the Emergency Department precipitated pain consistent with biliary colic; the pain resolved promptly after administration of naloxone. This entity may considered in the differential diagnosis of acute onset of colicky abdominal pain in the patient given narcotics.
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J. Pharmacol. Exp. Ther. · Jul 2001
Blockade of opioid receptors in rostral ventral medulla prevents antihyperalgesia produced by transcutaneous electrical nerve stimulation (TENS).
Although transcutaneous electrical nerve stimulation (TENS) is used extensively in inflammatory joint conditions such as arthritis, the underlying mechanisms are unclear. This study aims to demonstrate an opiate-mediated activation of descending inhibitory pathways from the rostral ventral medulla (RVM) in the antihyperalgesia produced by low- (4 Hz) or high-frequency (100 Hz) TENS. Paw withdrawal latency to radiant heat, as an index of secondary hyperalgesia, was recorded before and after knee joint inflammation (induced by intra-articular injection of 3% kaolin and carrageenan) and after TENS/no TENS coadministered with naloxone (20 microg/1 microl), naltrindole (5 microg/1 microl), or vehicle (1 microl) microinjected into the RVM. ⋯ The analgesia produced by DAMGO and deltorphin is selectively blocked by naloxone (p < 0.05) and naltrindole (p < 0.05), respectively. Thus, the dose of naloxone and naltrindole used in the current study blocks mu- and delta-opioid receptors, respectively. Hence, low-frequency and high-frequency TENS produces antihyperalgesia by activation of mu- and delta-opioid receptors, respectively, in the RVM.
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Nociceptin or orphanin FQ (N/OFQ) is the natural ligand of the opioid receptor-like 1 receptor (ORL-1), which has been also classified as the fourth member of the opioid family of receptors and named OP(4). Elucidation of the biological role of N/OFQ has been hampered by the lack of compounds that selectively block the OP(4) receptor. Recently, a N/OFQ derivative, [Nphe(1)]N/OFQ(1-13)NH(2), has been found to possess OP(4) antagonistic properties both in vitro and in vivo models. ⋯ Intrathecal (i.t.) administration of N/OFQ (0.2--20 nmoles) dose-dependently reversed mechanical allodynic-like behavior, while [Nphe(1)]N/OFQ(1-13)NH(2) (20--120 nmoles, i.t.) was ineffective on its own. [Nphe(1)]N/OFQ(1-13)NH(2) (60--120 nmoles, i.t.) antagonized N/OFQ (about 80% of reduction) but did not modify the activity of morphine (20 nmoles, i.t.). These results further support, for the first time in a chronic model of pain, the specific antagonistic profile of [Nphe(1)]N/OFQ(1-13)NH(2)vs the OP(4) receptor. This pseudopeptide is an interesting pharmacological tool to better clarify the role of N/OFQ in pathophysiology.
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Randomized Controlled Trial Clinical Trial
The impact of nalmefene on side effects due to intrathecal morphine at cesarean section.
Nalmefene is a long-acting opioid antagonist that provides long-term relief from side effects of intrathecal morphine sulfate. A randomized, double-blind, placebo-controlled study was conducted to determine whether prophylactic nalmefene could decrease side effects of intrathecal morphine given during cesarean section, without affecting analgesia. Sixty parturients were given 0.25 mg of intrathecal morphine, 12.5 micrograms of fentanyl, and 11.25 to 15 mg of bupivacaine. ⋯ Subjects who received nalmefene required supplemental analgesia at a median of 6.00 hours after intrathecal morphine, compared with 14.12 hours in the placebo group (P = .037). No differences were found between the groups in the incidence of pruritus, nausea and vomiting, level of sedation, or analgesic satisfaction. We concluded that nalmefene at a dose of 0.25 microgram/kg does not decrease the incidence of side effects but increases the need for supplemental analgesics.
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Alcohol. Clin. Exp. Res. · Jun 2001
Effects of ethanol and naltrexone in a model of traumatic brain injury with hemorrhagic shock.
Ethanol predisposes to traumatic injury and causes respiratory depression and cardiovascular compromise in models of traumatic brain injury (TBI) and hemorrhagic shock (HS). Endogenous opioids may play a role in ethanol intoxication and TBI. We studied the effects of ethanol and the opiate antagonist agent naltrexone (NTX) in a TBI/HS model. ⋯ In this TBI/HS model, NTX reverses ethanol-induced depression of hypercapnic ventilatory response but does not improve MAP, CPP, or metabolic acidosis. This suggests that the respiratory effects of ethanol in TBI, but not the hemodynamic effects, may be mediated by opiate receptor activation.