Hydroxyzine
Description: Hydroxyzine is a piperazine antihistamine (H1-blocker) that is structurally related to buclizine, cyclizine, and meclizine. Hydroxyzine is effective in treating histamine-mediated pruritus or pruritus due to atopy or other allergic conditions. Hydroxyzine has been used for many years as a perioperative sedative and anxiolytic. The drug is considered an effective alternative treatment for anxiety disorders (e.g., generalized anxiety). In pain management, experts have questioned the efficacy of hydroxyzine as an adjunct to meperidine and other opiate analgesics; however, narcotic dosage reduction may be possible with the concurrent use of hydroxyzine and may be of benefit in some clinical scenarios. The drug has been used to alleviate nausea and control emesis perioperatively, and is sometimes used adjunctively to other agents. The intramuscular (IM) dosage form has been used for the symptomatic management of acute alcohol withdrawal. Although many clinicians believe that hydroxyzine is one of the most sedating H1-blockers, a small study showed that hydroxyzine produced less sedation than either azatadine or clemastine.[23592] The active metabolite of hydroxyzine, cetirizine (see separate monograph), has also been developed as an antihistamine (H1-blocker). Hydroxyzine was originally approved by the FDA in 1956. Pfizer announced on May 4, 2004 that it had officially discontinued all product lines of the Atarax® brand name.
Mechanism of Action: Hydroxyzine competes with histamine for H1-receptor sites on the effector cell surface. Blockade of H1-receptors also suppresses the formation of edema, flare, and pruritus that result from histaminic activity. The sedative properties of hydroxyzine occur at the subcortical level of the CNS, and, as mentioned above, this effect may be dose-related. Hydroxyzine has some antiemetic actions secondary to its central anticholinergic actions. Hydroxyzine also demonstrates antiarrhythmic, analgesic, local anesthetic, and skeletal muscle relaxant properties as well as bronchodilatory and mild antisecretory effects. Although antihistamines possess intrinsic analgesic properties (perhaps secondary to interfering with nociception), they should not be considered potent analgesics.
Pharmacokinetics: Hydroxyzine is administered orally or intramuscularly. Distribution of hydroxyzine has not been fully described and it is unknown whether it crosses the placenta or is distributed into breast milk (see Contraindications). Hydroxyzine, like most first-generation antihistamines, is metabolized in the liver. One active metabolite is cetirizine; cetirizine is mostly excreted renally as unchanged drug. Another hydroxyzine metabolite, norchlorcyclizine, has chemical similarities to a trazodone metabolite, m-chlorophenylpiperazine, but the activity and elimination of this compound are not certain. The elimination half-life of hydroxyzine is variably reported to be between 14—25 hours.
•Route-Specific Pharmacokinetics
Oral Route
Hydroxyzine is rapidly absorbed following oral administration. The oral dosages of hydroxyzine pamoate and hydroxyzine hydrochloride are considered equivalent. The onset of effect for hydroxyzine occurs between 15—60 minutes, with a usual duration of action of 4—6 hours. The inflammatory response and pruritus can be suppressed for up to 4 days.
•Special Populations
Hepatic Impairment
Hydroxyzine elimination is impaired in patients with primary biliary cirrhosis; other patients with liver disease may have reduced drug elimination.
Renal Impairment
Patients with moderate to severe renal impairment may exhibit decreased rates of drug clearance and dosage adjustment of hydroxyzine is recommended. Hemodialysis does not appreciably remove hydroxyzine or cetirizine from the blood.
HydroxyzineDescription: Hydroxyzine is a piperazine antihistamine (H1-blocker) that is structurally related to buclizine, cyclizine, and meclizine. Hydroxyzine is effective in treating histamine-mediated pruritus or pruritus due to atopy or other allergic conditions. Hydroxyzine has been used for many years as a perioperative sedative and anxiolytic. The drug is considered an effective alternative treatment for anxiety disorders (e.g., generalized anxiety). In pain management, experts have questioned the efficacy of hydroxyzine as an adjunct to meperidine and other opiate analgesics; however, narcotic dosage reduction may be possible with the concurrent use of hydroxyzine and may be of benefit in some clinical scenarios. The drug has been used to alleviate nausea and control emesis perioperatively, and is sometimes used adjunctively to other agents. The intramuscular (IM) dosage form has been used for the symptomatic management of acute alcohol withdrawal. Although many clinicians believe that hydroxyzine is one of the most sedating H1-blockers, a small study showed that hydroxyzine produced less sedation than either azatadine or clemastine.[23592] The active metabolite of hydroxyzine, cetirizine (see separate monograph), has also been developed as an antihistamine (H1-blocker). Hydroxyzine was originally approved by the FDA in 1956. Pfizer announced on May 4, 2004 that it had officially discontinued all product lines of the Atarax® brand name.กลไกของการดำเนินการ: Hydroxyzine แข่งขัน ด้วยฮิสตามีนที่ตัวรับ H1 ไซต์บนพื้นผิวเซลล์ effector ขวางของ H1 receptors ยังไม่ใส่การก่อตัวของอาการบวมน้ำ กาง และอย่างไร pruritus ที่ได้จากกิจกรรม histaminic คุณสมบัติ sedative ของ hydroxyzine เกิดขึ้นที่ระดับ subcortical CNS ก ตามที่กล่าวข้างต้น ผลนี้อาจจะเกี่ยวข้องกับยา Hydroxyzine การกระทำ antiemetic รองการกระทำ anticholinergic ของกลางได้ Hydroxyzine สำแดง antiarrhythmic ยาระงับปวด ยา ชา และคุณสมบัติ relaxant กล้ามเนื้ออีกทั้ง เป็นลักษณะ antisecretory bronchodilatory และอ่อน แม้ว่ายาแก้แพ้มีคุณสมบัติระงับปวด intrinsic (บางทีถึงมัธยมรบกวน nociception), พวกเขาจะไม่ถือกันมีศักยภาพการเภสัชจลนศาสตร์: Hydroxyzine จัดการเนื้อหา หรือเข้ากล้ามเนื้อ กระจาย hydroxyzine ไม่ได้รับการอธิบายไว้เต็ม และไม่ทราบว่าตัดรก หรือกระจายในน้ำนม (ดูข้อห้ามใช้) Hydroxyzine เช่นยาแก้แพ้รุ่นมากที่สุด ถูก metabolized ในตับ เซทิไรซีน เป็น active metabolite หนึ่ง เซทิไรซีนเป็นส่วนใหญ่ excreted renally เป็นยาที่เปลี่ยนแปลง อื่น hydroxyzine metabolite, norchlorcyclizine มีความคล้ายคลึงทางเคมีให้ trazodone metabolite, m chlorophenylpiperazine แต่กิจกรรม และตัดของผสมนี้ไม่แน่ใจ Half-life ตัดของ hydroxyzine variably รายงานระหว่าง 14 – 25 ชั่วโมง•Route-Specific PharmacokineticsOral RouteHydroxyzine is rapidly absorbed following oral administration. The oral dosages of hydroxyzine pamoate and hydroxyzine hydrochloride are considered equivalent. The onset of effect for hydroxyzine occurs between 15—60 minutes, with a usual duration of action of 4—6 hours. The inflammatory response and pruritus can be suppressed for up to 4 days.•Special PopulationsHepatic ImpairmentHydroxyzine elimination is impaired in patients with primary biliary cirrhosis; other patients with liver disease may have reduced drug elimination.Renal ImpairmentPatients with moderate to severe renal impairment may exhibit decreased rates of drug clearance and dosage adjustment of hydroxyzine is recommended. Hemodialysis does not appreciably remove hydroxyzine or cetirizine from the blood.
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