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Adrenoceptor blocking drugs

Adrenoceptor blocking drugs. Classification:depend on the affinity for different groups of receptor α-adrenoceptor antagonists β-adrenoceptor antagonists α, β-adrenoceptor antagonists Adrenaline reversal. α-R blocking agents. reversible α-R blocking agents Phentolamine Tolazoline

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Adrenoceptor blocking drugs

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  1. Adrenoceptor blocking drugs

  2. Classification:depend on the affinity for different groups of receptor • α-adrenoceptor antagonists • β-adrenoceptor antagonists • α, β-adrenoceptor antagonists • Adrenaline reversal

  3. α-R blocking agents • reversible α-R blocking agents • Phentolamine • Tolazoline • irreversible α-R blocking agents • phenoxybenzamine

  4. Phentolamine and Tolazoline • Binds to α-R, producing an reversible blockage • competitive antagonists

  5. Pharmacological Effects • produces vasodialation, decrease peripheral resistance and increase venous capacity • reflex cardiac stimulation • stimulates salivary, lacrimal, pancreatic , respiratory tract and gastric secretion

  6. Therapeutic Uses • Peripheral vascular disease • control acute hypertension episodes caused by use of sympathemimetics • diagnostic test for pheochromocytoma • Antishock • heart failure with pulmonary edema

  7. Adverse reactions • Hypotension • Gastrointestinal reactions • arrhythmia

  8. Phenoxybenzamine • binds to the α-R, producing an irreversible blockage, more potent in blocking α-R • a little effects on His-R and 5-HT-R

  9. Pharmacological Effects • produce vasodialation, decrease peripheral resistance • diastolic pressure decrease • reflex cardiac stimulation • a little effects on His-R and 5-HT-R

  10. Therapeutic Uses • Peripheral vascular disease • Antishock • pheochromocytoma • BPH

  11. α1-R blocking agents • Selectively block α1-R • Prazosin, terazosin, tamsulosin, doxazosin • Therapeutic Uses: hypertension, BPH

  12. α2-R blocking agents • Selectively block Presynaptic α2-R, regulation in Periphery and CNS NA • Yohimbine

  13. β-R blocking agents • block the neurotransmitter and adrenomimetic drugs from adrenergic nerve ending to bind with β-R • competitive antagonists • nonselective β-R antagonist:competes for both β1-R and β2-R • β1-R antagonist

  14. Pharmacological Effects • Cardiovascular system • decrease the heart rate and cardiac output and prolongs systole • decrease the blood flow to most tissue • decrease the total coronary blood flow and oxygen consumption

  15. Pharmacological Effects • Bronchial smooth muscleincrease airway resistance by β-R blockade • Metabolism: carbohydrate and fat metabolism are mediated by β-R

  16. β1受体激动 普萘洛尔抑制 脂肪分解 α、β受体 兴奋 交感神经兴奋 肝糖原、肌糖原分解 血糖水平 降低 血糖水平 升高 糖原分解 肾上腺素增强 胰 岛 素 增 强 普萘洛尔抑制 普萘洛尔无作用 增强 儿茶酚胺反馈性 释放增加 普萘洛尔抑制

  17. Pharmacological Effects • membrane-stabilization action : quinidine like action and local anesthesia action • intrinsic sympathomimetic activity(ISA) • Antiplatelet, ocular pressure reduction

  18. Therapeutic Uses • tachycardia supraventricular and ventricular arrythmias, especially for sinus tachycardia • angina pectoris, myocardial infarction • Hypertension • BHF • Others: Hyperthyroidium

  19. Adverse reactions • Cardiovascular system • Asthma • Withdrawal reaction • Others: • Contraindication: Bradycardia, cardiac function insufficiency, severe A-V blocking, asthma

  20. Propranolol • Bioavailability: 30% • Interindividual variation • HR , cardiac output ,BP • Therapeutic Uses: arrythmias, hypertension, angina pectoris, hyperthyroidism

  21. otherβ-R antagents • Nadolol: more potent than propranolol, and half life are longer • Timolol: most potent, glaucoma • Pindolol：more potent than propranolol，ISA(β2-R)

  22. β1-R blocking agents • Atenolol, metoprolol • Little effect on β2-R • hypertension

  23. α、β-R blocking agents • Labetalol, bucindolol, arotinolol, amosulalol • More potent in blocking β-R • Major use in hypertension

  24. Labetalol • Bioavailability: 20-40% • ISA to β2-R • Therapeutic Uses: hypertension, angina pectoris

  25. arotinilol • α:β=1:8 • contractility decrease, HR • BP • Therapeutic Uses: hypertension, Supraventricular tachycardia, angina

  26. 传出神经系统药物对狗血压的影响 （实验记录）

  27. 结 果 解 释 • 静注肾上腺素可以兴奋α、β1受体。 • β受体兴奋可使心脏兴奋，心输出量增加，sp升高，dp不变或下降。 • β 受体对肾上腺素更敏感，所以肾上腺素浓度低时可出现后继性降压。 • 较大剂量静注时，由于血管α受体占优势，导致血管收缩，血压sp、dp均升高。

  28. 去甲肾上腺素可以兴奋血管的α受体，使外周血管收缩，血压增高，但作用时间短。去甲肾上腺素可以兴奋血管的α受体，使外周血管收缩，血压增高，但作用时间短。 • 麻黄碱的作用发生慢而温和，且比较持久，他可以直接作用于α、β受体，使心率加快，血管收缩，血压上升，也可以通过促使肾上腺素能神经末梢释放递质（主要是去甲肾上腺素），使血管α受体兴奋，血压上升。

  29. 大剂量乙酰胆碱静注可致N样作用，使心收缩力加强，小血管收缩而出现血压升高。大剂量乙酰胆碱静注可致N样作用，使心收缩力加强，小血管收缩而出现血压升高。 • 烟碱是N受体兴奋剂，小剂量兴奋 N2受体和中枢神经系统，也兴奋N1受体。预先使用阿托品仅仅阻断了M受体，故出现血压的迅速升高。

  30. 静注酚妥拉明后，阻断了α受体，使外周β兴奋占优势，血管扩张，同时酚妥拉明还可以直接舒张小动脉平滑肌，这两者均导致血压迅速下降。静注酚妥拉明后，阻断了α受体，使外周β兴奋占优势，血管扩张，同时酚妥拉明还可以直接舒张小动脉平滑肌，这两者均导致血压迅速下降。

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