Adrenoceptor blocking drugs

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Adrenoceptor blocking drugs

description

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 - PowerPoint PPT Presentation

Transcript of Adrenoceptor blocking drugs

Page 1: Adrenoceptor     blocking drugs

Adrenoceptor blocking drugs

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Classification:depend on the affinity for different groups of receptor α-adrenoceptor antagonists β-adrenoceptor antagonists α, β-adrenoceptor antagonists

Adrenaline reversal

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α-R blocking agents

reversible α-R blocking agents Phentolamine Tolazoline

irreversible α-R blocking agents phenoxybenzamine

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Phentolamine and Tolazoline

Binds to α-R, producing an reversible blockage

competitive antagonists

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Pharmacological Effects

produces vasodialation, decrease peripheral resistance and increase venous capacity

reflex cardiac stimulation stimulates salivary, lacrimal, pancr

eatic , respiratory tract and gastric secretion

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Therapeutic Uses

Peripheral vascular disease control acute hypertension episodes c

aused by use of sympathemimetics diagnostic test for pheochromocytom

a Antishock heart failure with pulmonary edema

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Adverse reactions

Hypotension Gastrointestinal reactions arrhythmia

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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

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Pharmacological Effects

produce vasodialation, decrease peripheral resistance

diastolic pressure decrease reflex cardiac stimulation a little effects on His-R and 5-H

T-R

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Therapeutic Uses

Peripheral vascular disease Antishock pheochromocytoma BPH

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α1-R blocking agents

Selectively block α1-R Prazosin, terazosin, tamsulosin,

doxazosin Therapeutic Uses: hypertension,

BPH

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α2-R blocking agents

Selectively block Presynaptic α2-R, regulation in Periphery and CNS NA

Yohimbine

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β-R blocking agents block the neurotransmitter and adrenom

imetic drugs from adrenergic nerve ending to bind with β-R

competitive antagonists nonselective β-R antagonist:competes fo

r both β1-R and β2-R β1-R antagonist

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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

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Pharmacological Effects

Bronchial smooth muscleincrease airway resistance by β-R blockade

Metabolism: carbohydrate and fat metabolism are mediated by β-R

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交感神经兴奋 β1 受体激动 脂肪分解普萘洛尔抑制

α 、 β 受体兴奋

肝糖原、肌糖原分解

糖原分解 肾上腺素增强 普萘洛尔抑制

血糖水平升高

胰 岛 素 增 强普萘洛尔无作用

血糖水平降低

普萘洛尔抑制儿茶酚胺反馈性释放增加

增强

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Pharmacological Effects

membrane-stabilization action : quinidine like action and local anesthesia action

intrinsic sympathomimetic activity(ISA)

Antiplatelet, ocular pressure reduction

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Therapeutic Uses

tachycardia supraventricular and ventricular arrythmias, especially for sinus tachycardia

angina pectoris, myocardial infarction

Hypertension BHF Others: Hyperthyroidium

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Adverse reactions

Cardiovascular system Asthma Withdrawal reaction Others: Contraindication: Bradycardia, card

iac function insufficiency, severe A-V blocking, asthma

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Propranolol Bioavailability: 30% Interindividual variation HR , cardiac output ,BP Therapeutic Uses: arrythmias, hyperte

nsion, angina pectoris, hyperthyroidism

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otherβ-R antagents Nadolol: more potent than propranol

ol, and half life are longer Timolol: most potent, glaucoma Pindolol : more potent than propran

olol , ISA(β2-R)

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β1-R blocking agents

Atenolol, metoprolol Little effect on β2-R hypertension

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α 、 β-R blocking agents

Labetalol, bucindolol, arotinolol, amosulalol

More potent in blocking β-R Major use in hypertension

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Labetalol

Bioavailability: 20-40% ISA to β2-R Therapeutic Uses: hypertension,

angina pectoris

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arotinilol α:β=1:8 contractility decrease, HR BP Therapeutic Uses: hypertension,

Supraventricular tachycardia, angina

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传出神经系统药物对狗血压的影响 (实验记录)

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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, s

p 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。

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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。

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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。

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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。