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It has been known for more than one hundred years that an intravenous injection of histamine causes a fall in the blood pressure. [30] The underlying mechanism concerns both vascular hyperpermeability and vasodilation. Histamine binding to endothelial cells causes them to contract, thus increasing vascular leak.
Vasoactive drug therapy is typically used when a patient has the blood pressure and heart rate monitored constantly. The dosage is typically titrated (adjusted up or down) to achieve a desired effect or range of values as determined by competent clinicians. Vasoactive drugs are typically administered using a volumetric infusion device (IV pump).
Postural hypotension is a common side effect of such drugs. Trimethaphan causes a histamine release which further lowers blood pressure. Effects on the heart include a decreased force of contraction and an increase in heart rate (tachycardia). Reflexive tachycardia can be diminished or undetected because trimetaphan is also blocking the ...
Vasodilation works to decrease vascular resistance and blood pressure through relaxation of smooth muscle cells in the tunica media layer of large arteries and smaller arterioles. [17] When vasodilation causes systolic blood pressure to fall below 90 mmHg, circulatory shock is observed. [11]
Betahistine is a weak antagonist or inverse agonist at histamine H₃ receptors and a weak partial agonist at histamine H₁ receptors. Betahistine primarily acts on histamine H₁ receptors located on blood vessels in the inner ear, leading to vasodilation and increased vascular permeability.
Quifenadine is a derivative of quinuclidylcarbinol, which reduces the effects of histamine on organs and systems. Quifenadine is a competitive blocker of H1 receptors. In addition, it activates the diamine oxidase enzyme, which breaks down about 30% of endogenous histamine.
In adults a systolic blood pressure of less than 90 mmHg is often used. [3] During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure, [3 ...
One of the factors believed to cause histamine intolerance is an imbalance between uptake of histamine through the diet and a diminished capacity to metabolize ingested histamine, leading to an increased blood concentration of the amines which may potentially cause adverse effects. The primary cause of histamine intolerance is considered by ...