Some adrenergic blocking agents have a specific affinity for alpha-receptor sites. Their use is somewhat limited because of the development of even more specific and safer drugs. Only one of these drugs, phentolamine (Regitine), is still used.
Phentolamine blocks the postsynaptic alpha1-adrenergic receptors, decreasing sympathetic tone in the vasculature and causing vasodilation, which leads to a lowering of blood pressure. It also blocks presynaptic alpha2-receptors, preventing the feedback control of norepinephrine release. The result is an increase in reflex tachycardia that occurs when blood pressure is lowered. Phentolamine is most frequently used to prevent cell death and tissue sloughing after extravasation of intravenous norepinephrine or dopamine, causing a local vasodilation and a return of blood flow to the area.
Phentolamine is rapidly absorbed after IV or IM injection and is excreted in the urine. There are few data on its metabolism and distribution.
酚妥拉明IV或IM注射后迅速吸收，随尿排出。其代谢和分布资料不多。
Contraindications and Cautions 禁忌与注意事项
Phentolamine is contraindicated in the presence of allergy to this or similar drugs and in the presence of coronary artery disease or MI because of the potential exacerbation of these conditions; it should be used cautiously in pregnancy or lactation because of the potential adverse effects on the fetus or neonate.
Patients receiving phentolamine often experience extensions of the therapeutic effects, including hypotension, orthostatic hypotension, angina, MI, cerebrovascular accident, flushing, tachycardia, and arrhythmia—all of which are related to vasodilation and decreased blood pressure. Headache, weakness, and dizziness often occur in response to hypotension. Nausea, vomiting, and diarrhea may also occur.
Clinically Important Drug–Drug Interactions 临床重要的药药相互作用
Ephedrine and epinephrine may have decreased hypertensive and vasoconstrictive effects if they are taken concomitantly with phentolamine because these agents work in opposing ways in the body. Increased hypotension may occur if this drug is combined with alcohol, which is also a vasodilator.
affinity – n. 亲和性，亲和力
phentolamine – n. 酚妥拉明 Regitine – n. 利其丁
postsynaptic – a. 突触后的
vasculature – n. 脉管系统，维管结构
presynaptic -- a. 突触前的
feedback control – 反馈控制
reflex tachycardia – 反射性心动过速
sloughing – n. 腐肉形成
extravasation – n. 外渗，外溢
concomitant – a. 同步，同时
opposing – a. 相对的
1. A client experiencing shortness of breath associated with asthma is given epinephrine (Adrenalin). This medication is considered a nonselective adrenergic drug because it innervates which receptor sites.
A. Alpha-adrenergic
B. Beta-adrenergic
C. Alpha-, beta1-, and beta2-adrenergic
D. Beta1 and beta2-adrenergic
2. Which of the following drugs can improve urine flow in males?
A. Prazosin
B. Nebivolol
C. Labetalol
D. Amiodarone
奥医教育“在线自测”正式上线，复习练习、效果检验，奥医NCLEX-RN/ISPN题库一站完成。
答案Answers
1. C. Alpha-, beta1-, and beta2-adrenergic Rationale: Epinephrine has powerful beta2 action that dilates bronchial airways and works on all receptor sites. 2. A. Prazosin Rationale: Prazosin, a selective alpha1-receptor adrenergic antagonist, can improve urine flow in male patients and are used as treatment for benign prostatic hypertrophy (BPH). This is because they can block smooth muscle receptors in the genitourinary tract which leads to relaxation of prostate and bladder.
当前位置：
