四、体内酸碱平衡对药物的分布和排泄的关系。药物的药理效应的发挥取决于和药物发生作用的受体所在部位(细胞内或细胞外),改变血浆的酸碱度可以改变组织细胞内外药物分布的浓度比例。如苯巴比妥为酸性药(药物受体在细胞内),在呼吸性酸中毒时,其非离子化型增加,它是脂溶性且易于透过细胞膜,药物进入细胞内与受体结合增多,药理作用增强,使昏迷的病人昏迷加深。当使用碳酸氢纳等改变血液酸碱度使细胞外液呈碱性后,就可使苯妥英钠的离子型积聚于细胞外(离开受体),药理效应即降低,患者的症状也随之减轻。降压药美加明是一种弱碱性药物,它的作用部位的受体在细胞外,因此,在酸中毒时,有利于它在细胞外积蓄,使受体部位的药物浓度增加,药理作用提高。尿的酸碱度改变,也可以明显地影响肾对弱酸性或弱碱性药物的排泌。弱酸性药物在碱性尿中呈大量的离子化 Fourth, the acid-base balance of the distribution and excretion of drugs in the relationship. The pharmacological effect of a drug depends on the site of the receptor (intracellular or extracellular) that interacts with the drug, and changing the pH of the plasma can change the concentration ratio of drug distribution inside and outside the tissue cell. Such as phenobarbital acidic drugs (drug receptors in the cell), in respiratory acidosis, its non-ionized type increases, it is fat-soluble and easy to penetrate the cell membrane, drugs into the cell and the receptor increased binding , Pharmacological effects increased, coma patients coma deepened. When sodium bicarbonate is used to alter the pH of the blood to make the extracellular fluid alkaline, the ionic phenytoin can accumulate outside the cell (leaving the receptor), reducing the pharmacological effects and alleviating the patient’s symptoms. Antihypertensive drugs Mecamin is a weakly basic drug, its role in the receptor site in the extracellular, therefore, in acidosis, is conducive to its accumulation in the extracellular, so that the drug concentration at the receptor site, pharmacological effects improve. Changes in urine pH, can also significantly affect the kidneys of weak acid or weak alkaline drugs excretion. Weak acid drugs in alkaline urine was a lot of ionization