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充血性心衰引起肺高压和右心充盈压高,导致肝和胃肠道瘀血;而且,胃肠道、肝和肾的灌注减少,可导致药物代谢改变。 1生物利用度是指服药后到达体循环的药量,在多数情况下这一名词用于口服药的生物利用度,按口服与静脉浓度一时间曲线的面积比率计算。药物在胃肠道的相互作用及其吸收和首次通过代谢(可发生在胃肠道、主要在肝)影响口服药物生物利用度。吸收:多数胃肠道吸收在空肠上部,吸收率和量与药物的物理化学特性、血流、吸收表面积和胃排空及肠的运动有关。胃排空率的改变改变了药物递送到小肠上部和脂溶性药物的吸收率。充血性心衰(CHF)时,由于交感神经的活动或麻醉性镇痛药和有抗胆碱作
Congestive heart failure causes elevated pulmonary hypertension and right heart filling, leading to liver and gastrointestinal bleeding; moreover, reduced perfusion of the gastrointestinal tract, liver and kidney can result in altered drug metabolism. 1 Bioavailability refers to the dose that reaches the systemic circulation after taking the drug. In most cases the term bioavailability for oral administration is calculated as the area ratio of oral to intravenous concentration over time. Drug interactions in the gastrointestinal tract and their absorption and first pass metabolism (which can occur in the gastrointestinal tract, mainly in the liver) affect oral drug bioavailability. Absorption: The majority of the GI tract is absorbed in the upper jejunum. Absorption and volume are related to the physicochemical properties of the drug, blood flow, surface area for absorption, and gastric emptying and intestinal motility. Changes in gastric emptying rate alter the rate of drug delivery to the upper intestine and to lipophilic drugs. Congestive heart failure (CHF), due to sympathetic activity or narcotic analgesics and anticholinergic