calcium channel blockers
DESCRIPTION
Calcium Channel BlockersTRANSCRIPT
Calcium Channel BlockersCalcium Channel Blockers
Zheng Zhang
Department of Pharmacology
School of Pharmaceutical Sciences
Central South University
A class of drugs that act by interfering with the A class of drugs that act by interfering with the
activity of Caactivity of Ca2+2+ channels on membrane, blocking channels on membrane, blocking
CaCa2+2+ influx, and decreasing the cytoplasmic levels influx, and decreasing the cytoplasmic levels
of Caof Ca2+2+
Calcium channel blockersCalcium channel blockers
(Calcium antagonist)(Calcium antagonist)
Physiological roles of CaPhysiological roles of Ca2+2+
Vascular smooth muscle tone maintenanceVascular smooth muscle tone maintenance
Myocardial contractionMyocardial contraction
Maintenance of cardiac automaticity and Maintenance of cardiac automaticity and
propagation propagation
Miscellaneous : cell proliferation, gland excretion, Miscellaneous : cell proliferation, gland excretion,
cellular migration, release of transmitters, blood cellular migration, release of transmitters, blood
coagulation.coagulation.
Sources of intracellular free calciumSources of intracellular free calcium
Calcium enflux through calcium channels Calcium enflux through calcium channels
Calcium release from the sarco- or Calcium release from the sarco- or
endoplasmic reticulum and mitochondriaendoplasmic reticulum and mitochondria
Classification of Classification of calciumcalcium channels channels
1.1. Voltage-dependent CaVoltage-dependent Ca2+2+ channel (VDCC) channel (VDCC) Opened during depolarization Opened during depolarization Six subtypes: T, L, N, P, Q, RSix subtypes: T, L, N, P, Q, R
2.2. Receptor-operated CaReceptor-operated Ca2+2+ channel (ROC): channel (ROC): Controlled by agonist, e.g. catecholamines Controlled by agonist, e.g. catecholamines
Insensitive to membrane depolarizationInsensitive to membrane depolarization
L-type calcium channel and mechanism L-type calcium channel and mechanism
of drug actionof drug action
1. L-type calcium channel1. L-type calcium channel
Components and structureComponents and structure Five subunits: Five subunits: 1, 1, 2, 2, , , , and , and Functional subunit: Functional subunit: 11
Channel structure and Channel structure and 1 subunit1 subunit
Menbrane
Outside
Inside
DHP: Dihydropyridine; PAA: Phenylalkylamines
2. Channel status and drug action2. Channel status and drug action
O
I R[Ca2+]i = Ca n p
[Ca2+]i: total calcium influx
Ca: single channel calcium influx
n: number of channels
p: probability of opening
+
Calcium channel blockers
II. Pharmacological actionsII. Pharmacological actions
1. Negative inotropic effect1. Negative inotropic effect
Decrease slow calcium influx during phase 2Decrease slow calcium influx during phase 2
contractility contractility
A. Heart:A. Heart:
2. Negative chronotropic and negative conductive
action
Slow Ca2+ influx in sinoatrial node automaticity
Slow Ca2+ influx in atrioventricular node conduction velocity
B. Vascular smooth muscle cells (VSMCs)B. Vascular smooth muscle cells (VSMCs)
1.1. Relax VSMCs and reduce BP, arterioles are more Relax VSMCs and reduce BP, arterioles are more
sensitive than veinssensitive than veins
2.2. Most potent in dilation the coronary arterialMost potent in dilation the coronary arterial
treatment for variant anginatreatment for variant angina
3.3. Nimodipine and Nicardipine are particularly selective for Nimodipine and Nicardipine are particularly selective for
cerebral blood vesselscerebral blood vessels
C. Other smooth muscle cellsC. Other smooth muscle cells
Relax bronchiolar, uterine and gastrointestinal SMCs
Selectivity of calcium blockers toward heart Selectivity of calcium blockers toward heart
and vasculatureand vasculature
Verapamil Verapamil heart heart vascular SMC vascular SMC
Nifedipine Nifedipine heart heart vascular SMC vascular SMC
Diltiazem Diltiazem heart heart vascular SMC vascular SMC
Blood pressure baroreceptor sense
sympathetic activity contractility and heart
rate
Reflex increase in heart rate
Nifedipine > Diltiazem > VerapamilNifedipine > Diltiazem > Verapamil
III. Therapeutic uses
1. Angina
Variant angina: dilate coronary artery,
first-line
Angina of effort: BP , afterload,
oxygen demand
2. Supraventricular arhythmia
Supraventricular tachycardia Verapamil is the first-selected agent
Supraventricular tachycardia caused by reentry
Verapamil is the first-selected agent
Sinus rhythm recovered in 80% patients
Use-dependence: channels being used
frequently are more susceptible to block
Atrial flutter (房扑 ) and fibrillation (房颤 )
Atriaventricular node (房室结 )
conduction ventricular rate
Ventricular tachycardia (室性心动过速 )
Caused by coronary spasm
No effect on other ventricular arrhythmia
3. Hypertension (3. Hypertension ( 高血压高血压 )) Efficacy correlates with baseline BP Efficacy correlates with baseline BP No effect in normotensivesNo effect in normotensives Advantages:Advantages:
1. Not affect cardiac output 2. Dilate renal vessels water and salt
excretion without water and salt retention3. Uric acid excretion 4. Decrease risk of shock5. Prevent and reverse cardiovascular
hypertrophy or remodeling
4. Myocardium infarction4. Myocardium infarction
Ischemia Ischemia membrane stability membrane stability , depolarization , depolarization
calcium influx , overload
activation of ATP consuming enzymes
energy tores susceptibility to damage
+
Calcium overload during MI:
energy stores
Ischemia
5. Congestive heart failure5. Congestive heart failure Therapeutic use is controversialTherapeutic use is controversial
Indications: CHF accompanied by angina or Indications: CHF accompanied by angina or
hypertensionhypertension
Efficacy in ventricular diastolic dysfunction > Efficacy in ventricular diastolic dysfunction >
ventricular systolic dysfunction ventricular systolic dysfunction
6. Hypertrophic myocardiopathy
Contraindications: left heart failure, sick sinus
syndrome, atrioventricular block
7. Atherosclerosis (AS, 7. Atherosclerosis (AS, 动脉粥样硬化动脉粥样硬化 ) )
Prevent or attenuate the Prevent or attenuate the
development of ASdevelopment of AS
Decrease CaDecrease Ca2+2+ in cytoplasm in cytoplasm
Inhibit platelet aggregationInhibit platelet aggregation
Dilate vasculatureDilate vasculature
Inhibit proliferation (Inhibit proliferation ( 增殖增殖 ) of vascular SMC) of vascular SMC
8. Vascular disease8. Vascular disease Cerebral vascular spasm and cerebral ischemia Cerebral vascular spasm and cerebral ischemia
((脑血管痉挛和脑缺血脑血管痉挛和脑缺血 ))
Subarachnoid hemorrhage (Subarachnoid hemorrhage ( 朱网膜下腔出血朱网膜下腔出血 ))
Primary pulmonary hypertensionPrimary pulmonary hypertension
Peripheral vascular disease: Raynaud’s Peripheral vascular disease: Raynaud’s
phenomenon (phenomenon ( 雷诺病雷诺病 ))
IV. PharmacokineticsIV. Pharmacokinetics
Easily absorbed after oral intake ( > 90%) Extensive first pass elimination Metabolism in liver by cytochrome P450s
(CYP3A4)
Most have short half-lives (t1/2=3~8 h)
Be cautious in hepatic dysfunction
Headache, Headache,
fatigue (fatigue ( 乏力乏力 ),),
heart-throb (heart-throb ( 心悸心悸 ),),
constipation (constipation ( 便秘便秘 ), ),
anklebone (anklebone ( 踝关节踝关节 ) edema) edema
V. Adverse reactionV. Adverse reaction
Cardiac inhibition Cardiac inhibition
VI. Classification of CCBsVI. Classification of CCBs
1.1. Phenyalkylamines (Phenyalkylamines ( 苯烷胺类苯烷胺类 ): ): e.g. e.g.
Verapamil (Verapamil ( 维拉帕米维拉帕米 ), and Anipamil (), and Anipamil ( 阿尼帕阿尼帕米米 ))
2.2. Dihydropyridines (Dihydropyridines ( 二氢吡啶类二氢吡啶类 ): ): Nifedipine Nifedipine
(( 硝苯地平硝苯地平 ), Nomodipine (), Nomodipine ( 尼莫地平尼莫地平 ), ),
Nicardipine (Nicardipine ( 尼卡地平尼卡地平 ), Felodipine (), Felodipine ( 非洛地非洛地平平 ), Amlodipine (), Amlodipine ( 氨氯地平氨氯地平 ))
3.3. Benzothiazepines (Benzothiazepines ( 地尔硫 类地尔硫 类 ): ): e.g. e.g.
Diltiazem (Diltiazem ( 地尔硫 卓 地尔硫 卓 ))
卓卓
A. Actions
1. Vasodilation ( 扩张血管 ) Peripheral and lung resistant vessel beds Coronary artery
Nifedipine (Nifedipine ( 硝苯地平硝苯地平 ))
2. Heart: positive inotropic ( 正性肌力 ) effect
Reflex sympathetic activity Reflex sympathetic activity myocardium myocardium
contractility contractility
B. Therapeutics uses
1.1. HypertensionHypertension
2.2. Variant anginaVariant angina
3.3. Heart failure:Heart failure: acute left ventricular acute left ventricular
failure caused by ischemia or failure caused by ischemia or
hypertensionhypertension
4.4. Others:Others: pulmonary hypertension pulmonary hypertension
(( 肺动脉高压肺动脉高压 ), Raynaud’s disease ), Raynaud’s disease
(( 雷诺病雷诺病 ))
C. Adverse reactions :Headache, hypotension, flush, peripheral Headache, hypotension, flush, peripheral
edema, tachycardiaedema, tachycardia
D. ContraindicationsD. Contraindications
Be Cautious in HF and unstable angina
Nitrendipine (Nitrendipine ( 尼群地平尼群地平 ))
Vasodilation activity 6-fold higher than Vasodilation activity 6-fold higher than
nifedipinenifedipine Inhibit secretion of aldosterone (Inhibit secretion of aldosterone ( 醛固酮醛固酮 )) Long-acting, tLong-acting, t1/21/2 = 7 ~ 8 hours = 7 ~ 8 hours Therapeutic use: hypertension and anginaTherapeutic use: hypertension and angina
Nisodipine ( 尼索地平 )
The strongest CCBThe strongest CCB Highly selective for coronary arteryHighly selective for coronary artery Rapidly absorbed with low bioavailabilityRapidly absorbed with low bioavailability Therapeutic use: hypertension and anginaTherapeutic use: hypertension and angina
Nicardipine
Selective for cerebral vessels and coronary Selective for cerebral vessels and coronary
arteryartery Inhibits phosphodiesterase (Inhibits phosphodiesterase ( 磷酸二酯酶磷酸二酯酶 )) Therapeutic use: hypertension, angina, Therapeutic use: hypertension, angina,
cerebral vasospasm and ischemiacerebral vasospasm and ischemia
Nimodipine
Highly selective for cerebral vesselsHighly selective for cerebral vessels Preserves and promotes memoryPreserves and promotes memory Therapeutic use: cerebral vasospasm and Therapeutic use: cerebral vasospasm and
ischemia, subarachnoid hemorrhageischemia, subarachnoid hemorrhage
Amlodipine
Slow but Slow but long acting, tlong acting, t1/21/2 = 35 ~ 50 hours = 35 ~ 50 hours
Bioavailability: 60% ~ 65%Bioavailability: 60% ~ 65% Therapeutic use: hypertension and anginaTherapeutic use: hypertension and angina
Verapamil (Isoptin)Verapamil (Isoptin)
Negative inotropic effect
Blocks calcium channel; activates phosphodiesterase;
inhibits the function of systolic proteins
Negative chronotropic effect
↑P-R interval— dose dependent
Vasodilation
Resistant vessels and coronary artery
Reflex sympathetic activity is mild
A. Actions :
B. Therapeutics usesB. Therapeutics uses
1.1. Supraventricular tachycardiaSupraventricular tachycardia
2.2. Angia (variant)Angia (variant)
3.3. HypertensionHypertension
4.4. Hypertrophic myocardiopathyHypertrophic myocardiopathy
C. Adverse reaction
1. Constipation, flush, headache, itch
2. Large doses: atrioventricular blockade
3. Most serious: hypotension (i.v)
A. Actions
1. Negative inotropic effect
2. Negative chronotropic effect
3. Vasodilation of coronary artery and its branches,
and peripheral resistant vessels
4. Ameliorates myocardial metabolism and protects
the function of mitochondria
Diltiazem
B. Therapeutics uses
1.1. Supraventricular tachycardiaSupraventricular tachycardia
2.2. Variant angina and angina of effort Variant angina and angina of effort
3.3. HypertensionHypertension
4.4. Hypertrophic myocardiopathyHypertrophic myocardiopathy
C. Adverse reaction
Rash, constipation, headache, flushing, dizziness, Rash, constipation, headache, flushing, dizziness, angioneurotic edemaangioneurotic edema
D. D. ContraindicationsContraindications
The same as verapamilThe same as verapamil