Cardiovascular system opioid effects

Fentanyl is primarily used alone, but sometimes it is combined with other opiates such as Licodaine, Bupiva-caine, or morphine in epidural administration or in some I Vs. However, one of the more appealing virtues of fentanyl is that, unlike other opioids, it has a very mild effect on the emetic trigger zone of the medulla. For this reason, patients have less nausea and no vomiting when fentanyl is used. With other drugs, such as morphine, this unwanted side effect can be intense. Fentanyl also does not cause the release of histamine, which makes it safer for the cardiovascular system than morphine. 

Tonazocine is a partial opioid receptor agonist that has not been reported to have adverse effects on the cardiovascular system or to cause clinically significant respiratory depression. When single doses of tonazocine 2,4, and 8 mg were compared in 150 adults postoperatively. 

Propoxyphene is an agonist of opioid fi receptors. It is this opioid effect that is responsible for the central nervous system and respiratory depression seen in overdose. Both propoxyphene and norpropoxyphene are potent blockers of myocardial sodium channels, an effect identical to type lA antidysrhythmic agents. This myocardial sodium channel blockade may result in prolongation of the electrocardiogram QRS complex, arrhythmias, and cardiovascular depression seen in propoxyphene poisoning. 

Fentanyl, sufentanil, and alfentanil are frequently used before anesthesia and surgery as a sedative and analgesic, as well as a continuous infusion for primary anesthesia. Because opioids rarely affect the cardiovascular system, they are particularly useful for cardiac surgery and other high-risk cases. Opioids act directly on spinal cord receptors, and are frequently used in epidurals for spinal anesthesia. Side effects may include nausea and vomiting, itching, and respiratory depression. 

CARDIOVASCULAR SYSTEM In the supine patient, therapeutic doses of morphine-like opioids have no major effect on blood pressure or cardiac rate and rhythm. Such doses do produce peripheral vasodilation, reduced peripheral resistance, and an inhibition of baroreceptor reflexes. Therefore, when supine patients assume the upright position, orthostatic hypotension and fainting may occur. The peripheral arteriolar and venous dilation produced by morphine involves several mechanisms. Morphine and some other opioids provoke release of histamine, which sometimes plays a large role in the hypotension. However, vasodilation usually is only partially blocked by Hj antagonists, but it is effectively reversed by naloxone. Morphine also blunts the reflex vasoconstriction caused by increased Pco (see Chapter 15). 

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. 

The opioids are considered relahvely safe from a cardiovascular standpoint. Myocardial depression is minimal. Changes in heart rate are species dependent and usually manifest as a mild decrease in heart rate however, a significant increase in heart rate can be seen in horses, which is consistent with the central excitatory effect that often occurs. Opioids inhibit the baroreceptor reflex response to changes in blood pressure. Certain opioids may cause systemic vasodilatation, decreased peripheral vascular resistance and hypotension secondary to histamine release. Morphine and meperidine (pethidine) are the opioids most likely associated with this effect. This is typically seen after rapid i.v. administration, is dose dependent and does not result from mast cell... 

The conorfamides, isolated from Conus spurius, belong to the RFamide neuropeptide family and may act as an agonist of the FMRF-amide-gated ion channels. In invertebrates, this peptide family has many diverse functions, whereas in the mammalian system they moderate opioid function in the CNS, modulate epithelial Na" " channels, have important cardiovascular effects, and stimulate pancreatic somatostatin secretion. ... 

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