Bannwarth Bernard, Péhourcq Fabienne
Service de Rhumatologie, Groupe Hospitalier Pellegrin & Laboratoire de Thérapeutique, EA 525, Université Victor Segalen, Bordeaux, France.
Drugs. 2003;63 Spec No 2:5-13.
The advantage of paracetamol (acetaminophen) is that it can be administered via the oral, intravenous or rectal routes. The last mentioned differs from the oral route in the slow and irregular absorption of the active substance. At therapeutic concentrations, the pharmacokinetics of paracetamol are linear--that is, independent of the dose, and constant with repeated administration. The efficacy of paracetamol has been demonstrated in a wide variety of acute or chronic painful syndromes. In adults, the optimum unit dose is 1 g. The maximum daily dosage is 4 g, consistent with the decline in analgesic activity, which is usually over 6 hours. With effervescent tablets, drug absorption and onset of action are more rapid than with conventional tablets. However, there is no direct correlation between serum concentrations of paracetamol and its analgesic or antipyretic effect. Paracetamol is the non-opiate analgesic of choice in elderly persons or patients with chronic renal insufficiency, and it is usually not necessary to reduce the dosage in such individuals, even though clearance is reduced. Although the bioavailability of paracetamol is not impaired in patients with chronic, benign liver diseases, the agent is contraindicated in those with hepatic insufficiency. It can be used during pregnancy and lactation. The very low level of paracetamol binding to plasma proteins, together with its hepatic metabolism, mainly through glucuronide or sulphate conjugation, account for the low risk of drug interactions with paracetamol, particularly with antivitamin K. When added to a traditional non-steroidal anti-inflammatory drug, paracetamol enhances the analgesic effect or allows the use of lower doses. It is more difficult to define the ideal dosage of paracetamol in children, because of the influence of age on its pharmacokinetics, and the relatively erratic bioavailability of suppositories. An oral dose of 15 mg/kg every 4 hours, up to a total of 60 mg/kg/day, is usually sufficient to achieve the desired analgesic or antipyretic effect.
对乙酰氨基酚（扑热息痛）的优点是可以通过口服、静脉注射或直肠给药途径使用。最后提到的直肠给药途径与口服途径的不同之处在于活性物质吸收缓慢且不规则。在治疗浓度下，对乙酰氨基酚的药代动力学呈线性，即与剂量无关，且重复给药时保持恒定。对乙酰氨基酚的疗效已在多种急性或慢性疼痛综合征中得到证实。在成年人中，最佳单位剂量为1克。最大日剂量为4克，随着镇痛活性下降，通常持续6小时以上。泡腾片的药物吸收和起效比传统片剂更快。然而，对乙酰氨基酚的血清浓度与其镇痛或解热作用之间没有直接相关性。对乙酰氨基酚是老年人或慢性肾功能不全患者的首选非阿片类镇痛药，即使清除率降低，这类患者通常也无需减少剂量。虽然慢性良性肝病患者的对乙酰氨基酚生物利用度未受损害，但肝功能不全患者禁用该药物。它可在妊娠和哺乳期使用。对乙酰氨基酚与血浆蛋白的结合水平极低，再加上其主要通过葡萄糖醛酸或硫酸结合进行肝脏代谢，这使得对乙酰氨基酚与其他药物发生相互作用的风险较低，尤其是与抗维生素K的相互作用。当与传统非甾体抗炎药合用时，对乙酰氨基酚可增强镇痛效果或允许使用更低剂量。由于年龄对其药代动力学的影响以及栓剂相对不稳定的生物利用度，确定儿童对乙酰氨基酚的理想剂量更为困难。通常每4小时口服15毫克/千克，每日总量达60毫克/千克，通常足以达到所需的镇痛或解热效果。
