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Gastrointestinal tract opioid effects

Mechanism of action Opioids exert their major effects by interacting with opioid receptors in the CNS and the gastrointestinal tract. Opioids cause hyperpolarization of nerve cells, inhibition of nerve firing, and presynaptic inhibition of transmitter release. Morphine acts at k receptors in lamina I and II of the substantia gelatinosa of the spinal cord, and decreases the release of substance P, which modulates pain perception in the spinal cord. Morphine also appears to inhibit the release of many excitatory transmitters from nerve terminals carrying nociceptive (painful) stimuli. [Pg.146]

Opioids are easily absorbed subcutaneously and intramuscularly, as well as from the gastrointestinal tract, nasal mucosa (e.g., when heroin is used as snuff), and lung (e.g., when opium is smoked). About 90% of the excretion of morphine occurs during the first 24 hours, but traces are detectable in urine for more than 48 hours. Heroin (diacetyhnorphine) is hydrolyzed to monoacetylmorphine, which is then hydrolyzed to morphine. Morphine and monoacetylmorphine are responsible for the pharmacologic effects of heroin. Heroin produces effects more rapidly than morphine because it is more lipid soluble and therefore crosses the blood-brain barrier faster. In the urine, heroin is detected as free morphine and morphine glucuronide (Gutstein and Akil 2001 Jaffe et al. 2004). [Pg.63]

The 5-HT3 receptor is the only monoamine neurotransmitter receptor that functions as a lig-and-gated ion channel, controlling the flux of Na-i- and K+ ions. 5-HT3 receptors are located on parasympathetic nerve terminals in the gastrointestinal tract, and high densities are found in areas of the brain associated with the emetic response, such as the area postrema. The antiemetic effects of 5-HT3 antagonists, such as ondansetron, result from actions at these sites. 5-HT3 receptors in the dorsal horn of the spinal cord have been implicated in nociception and development of new 5-HT3 receptor-related compounds may have potential as non-opioid, non-addictive analgesics. [Pg.22]

Opioids act by attaching to specific proteins called opioid receptors, which are found in the brain, spinal cord, and gastrointestinal tract. When these compounds attach to certain opioid receptors in the brain and spinal cord, they can effectively change the way a person experiences pain. [Pg.235]

The well-known antidiarrheal effect of opioids has been therapeutically exploited for many years. Diarrhea involves both an increase in the motility of the gastrointestinal tract and a decrease in the absorption of fluid and thus a loss of electrolytes (particularly sodium) and water. [Pg.286]

Tramadol is an opioid with additional actions the basis of its analgesic effects appears to derive from a combination of (relatively weak) agonist action on p-receptors, inhibition of neuronal noradrenaline uptake and enhanced serotonin release. It is rapidly absorbed from the gastrointestinal tract, 20% of an oral dose undergoes first-pass metabolism and less than 30% dose is excreted unchanged in the urine (W2 6 h). Tramadol is approximately as effective as pethidine for postoperative pain and as morphine for moderate chronic pain. [Pg.342]

Fedotozine (Jo-1196,170), which is structurally related to the acyclic k agonists, has in vivo antinociceptive effects on duodenal pain that appear to be mediated by peripheral k opioid receptors, but the compound is inactive after central administration (544). In binding assays (in dog myenteric plexus), however, this compound exhibits similar affinity = 0.3-0.8 jM) for all three types of opioid receptors (545). Unlike other k agonists, fedotozine does not induce diuresis after either s.c. or in-tracerebroventricular (i.c.v.) administration (546). Fedotozine also fails to substitute for either U50,488 or morphine in animals trained to discriminate these drugs (547). The main effects demonstrated for fedotozine have been in the gastrointestinal tract (seeRef 548 for a detailed review of the pharmacology of fedotozine), and therefore this compound has... [Pg.395]

Opioids share related pharmacologic attributes and exert a profound effect on the CNS and gastrointestinal tract. Mood changes, sedation, respiratory depression, nausea, vomiting, decreased gastrointestinal motility, dependence, and tolerance are evident in varying... [Pg.1093]

Caseinomorphins. Several peptides with opioid activity have been isolated from enzymatic digests of milk proteins (see Fox and Flynn, 1992). Such peptides were first isolated from enzymatic digests of casein and characterized as a family of peptides containing 4-7 amino acids with a common N-terminal sequence, H.Tyr.Pro.Phe.Pro-, and 0-3 additional residues (Gly, Pro, He), i.e. residues 60-63/6 of -casein, and hence were called caseinomorphins (P-CM) 4 to 7, respectively. P-CM-5 is the most effective of these peptides, which are 300-4000 times less effective than morphine. P-CMs are very resistant to enzymes of the gastrointestinal tract (GIT) and appear in the contents of the small intestine following ingestion of milk. -CN f60-70 also has weak opiate activity but may be hydrolysed to smaller, more active P-CMs by peptidases in the brush border of the GIT. [Pg.233]

Gastrointestinal constipation and nausea are common. Nausea may be treated with antiemetics, and frequently improves with ongoing therapy. Virtually all patients taking opioids become constipated and do not become tolerant to this side effect. Activation of mu receptors in the gastrointestinal tract slows peristalsis, which promotes further absorption of water and electrolytes in the colon. Patients should be treated prophylactically with stool softeners and/ or laxatives. There is an oral oxycodone/naloxone prolonged-release tablet in clinical trials to counteract opioid-induced constipation, which is often debilitating. [Pg.104]

Receptor interactions the primary effects of methyinaltrexone are mediated by antagonism of mu opioid receptors in the gastrointestinal tract. These receptors are primarily concentrated in neural cells and termi-... [Pg.418]

Because alvimopan reverses the adverse effects of opioids on the gastrointestinal tract, it accelerates gastrointestinal recovery in patients following colorectal or small-bowel resection surgery. This potentially improves patient comfort while reducing healthcare expenditure due to extended hospitalization. [Pg.422]

Patients with long-term or intermittent opioid therapy, including any opioid use a week prior to administration of alvimopan, could be more sensitive to its adverse effects. These effects, such as abdominal pain, nausea and vomiting, as well as diarrhea, are limited to the gastrointestinal tract. [Pg.422]

The predominant action of cannabinoid receptor agonists on the GI tract is an inhibitory effect on gastrointestinal motility, reminiscent of the neuromodulatory response to presynaptic p-opioid receptor or 02 -adrenoceptor activation of cholinergic, postganglionic parasympathetic neurons. The mechanisms underlying this effect have been studied chiefly in the GI tract of small rodents, but also in man and the pig. Here we shall review the findings of studies carried out in vitro (Sect. 3.1, below) and in vivo (Sect. 3.2). [Pg.577]

It is absorbed both neuraxially and systemically. DepoDur has a principal effect on opioid receptors in the dorsal horn of the spinal cord as well as in other regions of the central nervous system (CNS). Additionally, it works in the gastrointestinal (GI) tract and other smooth muscles. However, it does not have a major effect on the cardiovascular system at therapeutic doses. [Pg.194]


See other pages where Gastrointestinal tract opioid effects is mentioned: [Pg.51]    [Pg.21]    [Pg.493]    [Pg.130]    [Pg.693]    [Pg.702]    [Pg.712]    [Pg.285]    [Pg.443]    [Pg.444]    [Pg.144]    [Pg.524]    [Pg.435]    [Pg.252]    [Pg.90]    [Pg.278]    [Pg.305]    [Pg.387]    [Pg.97]    [Pg.118]    [Pg.119]    [Pg.418]    [Pg.421]    [Pg.497]    [Pg.432]    [Pg.397]   


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