Blood pressure dose-dependent changes

The antioxidant property of ferulic acid and related compounds from rice bran was reported by Kikuzaki et al, (2002). Their results indicated that these compounds elicit their antioxidant function through radical scavenging activity and their affinity with lipid substrates. Another recent study reported by Butterfield et al, (2002) demonstrated that ferulic acid offers antioxidant protection against hydroxyl and peroxyl radical oxidation in synaptosomal and neuronal cell culture systems in vitro. The effect of ferulic acid on blood pressure (BP) was investigated in spontaneously hypertensive rats (SHR). After oral administration of ferulic acid the systolic blood pressure (SBP) decreased in a dose-dependent manner. There was a significant correlation between plasma ferulic acid and changes in the SBP of the tail artery, suggesting... 

Hemodynamic changes Hemodynamic changes, manifested as decreases in blood pressure and increases in pulse rate, principally at doses more than 20 meg, were observed during clinical studies, and appeared to be dose-dependent. 

With large doses, thiopental causes dose-dependent decreases in arterial blood pressure, stroke volume, and cardiac output. This is due primarily to its myocardial depressant effect and increased venous capacitance there is little change in total peripheral resistance. Thiopental is also a potent respiratory depressant, lowering the sensitivity of the medullary respiratory center to carbon dioxide. 

Multiple sites in the CNS are affected by LSD. The drug shows serotonin (5-HT) agonist activity at presynaptic receptors in the midbrain, binding to both 5-HT and 5-HT2 receptors. Activation of the sympathetic nervous system occurs, which causes pupillary dilation, increased blood pressure, piloerection, and increased body temperature. Taken orally, low doses of LSD can induce hallucinations with brilliant colors, and mood alteration occurs. Tolerance and physical dependence have occurred, but true dependence is rare. Adverse effects include hyperreflexia, nausea, and muscular weakness. Sometimes high doses produce long-lasting psychotic changes in susceptible individuals. Haloperidol (see p. 127) and other neuroleptics can block the hallucinatory action of LSD and quickly abort the syndrome. 

In order to determine whether the mechanism of action of the cannabin-oids originates in the CNS, various cannabinoids were administered into the cerebral ventricles of New Zealand albino rabbits [171]. No change in the intraocular pressure was noted, although on intravenous administration d9-THC produced dose-dependent ocular hypotension and miosis. Apparently, the action of the cannabinoids on IOP does not originate in the CNS, and the authors surmise that alterations in blood pressure may be involved in the ocular hypotension. It is surprising that d8-THC did not cause ocular hypotension on i.v. administration as zf8-THC and J9-THC are generally assumed to have the same pharmacological profile. 

The overall effect of a sympathomimetic depends on the site of action (receptor agonist or indirect action), on receptor specificity and on dose for instance adrenaline ordinarily dilates muscle blood vessels (Pj mainly arterioles, but veins also) but in very large doses constricts them (a). The end results are often complex and unpredictable, partly because of the variability of homeostatic reflex responses and partly because what is observed, e.g. a change in blood pressure, is the result of many factors, e.g. vasodilatation (p) in some areas, vasoconstriction (a) in others, and cardiac stimulation (P). 

Milrinone is a phosphodiesterase type III/IV inhibitor that has vasodilatory properties and increases the force of contraction and velocity of relaxation of cardiac muscle. Milrinone has not been evaluated fully in the equine clinical setting. It produces a dose-dependent increase in heart rate, cardiac output, arterial blood pressure and ejection fraction and a reduction in right atrial, pulmonary artery pressures and systemic vascular resistance in normal anesthetized horses (Muir 1995). These changes persisted for 30 min after the termination of a constant i.v. infusion of milrinone. 

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... 

Barbiturates are associated with dose-dependent cardiovascular depression. However, because of preservation of the baroreceptor reflex, the hemo-d3mamic response to an induction dose of thiopental is mild. Heart rate generally increases to compensate for a brief fall in arterial blood pressure. As a result of this reflex response, blood pressure remains unchanged and cardiac output may increase slightly with the elevation in heart rate (Ilkiw et al 1991). Without the compensatory heart rate response, or if the change in heart rate is small, a decrease in systemic blood pressure and cardiac output would predominate. 

Changes in blood pressure induced by OPC (sarin, tabun, DFP, thiophos, octamethyl, carbophos, mercaptophos, trichlorfon, DDVP) depend significantly upon a dose administered. High (lethal) doses induce a persistent fall in blood pressure, which is usually preceded by short-term hypertension. On the contrary, an effect of low doses can be accompanied by a rise in blood pressure [5, 6],... 

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