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Calcium antagonists.pptx 1

Calcium antagonists are a class of drugs that work by blocking calcium channels. The main classes are verapamil, nifedipine, and diltiazem. They are used to treat angina, hypertension, arrhythmias, and other conditions. They work by decreasing intracellular calcium levels, leading to smooth muscle relaxation and reduced heart contractility. Common side effects include low blood pressure, heart block, and headaches.

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CALCIUM ANTAGONISTS Presented by Bibek Nepal Kuber Bajgain
EXCITATION–CONTRACTION COUPLING MUSCLE o Stimulation of the cardiac cell initiates the process of excitation, which has been related to ion fluxes through the cell membrane. Depolarization of the tissue in the atria of the heart is mediated by two inwardly directed ionic currents. i. Fast sodium current via Na+ channel ii. Current caused by slow activation of an L-type Ca++ channel
EXCITATION–CONTRACTION COUPLING MUSCLE Contraction of cardiac and other muscle occurs from a reaction between actin and myosin the contractile process in cardiac muscle involves a complex of proteins (troponins I, C, and T and tropomyosin) attached to myosin, which modulates the interaction between actin and myosin.
EXCITATION–CONTRACTION COUPLING MUSCLE
CALCIUM CHANNEL BLOCKERS Three important classes of CCBs a) Verapamil - a phenyl alkylamine (hydrophilic papaverine) b) Nifedipine - a dihydropyridine ( lipohilic) c) Diltiazem – a hydrophilic benzothiazepine
CALCIUM CHANNEL BLOCKERS Pharmacolgical actions All three subclasses of CCBs inhibit calcium mediated slow channel component of AP in a) Smooth muscle : o The CCBs decrease intracellular availability of Ca+2 and causes relaxation o Dihydropyridines (nifedipine) has most marked smooth muscle relaxant property.
CALCIUM CHANNEL BLOCKERS Pharmacolgical actions b) Heart o CCBs have negative inotropic effect o Verapamil has shown to have higher cardiodepressant action * Diltiazem has shown to have intermediate cardio depressant effect and vasodilation
CALCIUM CHANNEL BLOCKERS Indications o Angina o Hypertension o Raynaud’s syndrome o Supraventricular tachycardia and arrhythmias o Atrial fibrillation o Delay of preterm labor o Prophylaxis of cluster headache
CALCIUM CHANNEL BLOCKERS Adverse effect o Myocardial effects : hypotension , heart failure o Conduction effect : heart block , arrhythmias o Vascular smooth muscle : flushing , edema , headache rashes o Other effect : constipation , nausea , photosensitivity
VERAPAMIL o Verapamil is chemically 5-[(3,4 dimethoxyphenethyl) methylamino]-2-(3,4 dimethoxyphenyl)-2- isopropylvaleronitrile (Calan, Isoptin) o a coronary vasodilator and is the prototype of the Calcium antagonists used in cardiovascular diseases. C H 2 C H 2 N C H 2 C H 2 C H 2 C C H 3 C H ( C H 3 ) 2 O C H 3 O C H 3 H 3 C O H 3 C O C N
VERAPAMIL Properties o It is white crystalline powder, soluble in water freely soluble in methanol, sparingly soluble in ethanol o It should be stored in well closed container
VERAPAMIL Synthesis: H3CO H3CO C H CH CN H3C CH3 + OCH3 OCH3(CH2)2N CH3 (H2C)3 Cl 3,4-Dimethoxy phenyl ethyl-N-methyl- -3chloro propylamine 3,4- Dimethoxy-2-isopropyl valero nitrile CH2CH2NCH2CH2CH2C CH3 CH(CH3)2 OCH3 OCH3 H3CO H3CO CN-HCl VERAPAMIL
NIFEDIPINE Nifedipine is chemically 1,4-dihydro-2, 6-dimethyl-4- (2- nitrophenyl)-3,5-pyridinedicarboxylate dimethyl ester (Adalat, Procardia) N O 2 H NH 3 C C H 3 H 3 C O O C C O O C H 3 N i f e d i p i n e
NIFEDIPINE o It is yellow crystalline powder sparingly soluble in ethanol, insoluble in water but freely soluble in acetone o When exposed to day light or artificial light of certain wavelength it readily converts to nitrosophenylpyrimidine derivative and exposure to UV rays leads to formation of nitrophenylpyrimidine. o Hence it should be stored in light resistant airtight container
NIFEDIPINE Synthesis Step 1:preparation of Methyl-[2-acetyl-3-(2- nitropheny)]-2-propionate CHO NO2 2-nitro bendaldehyde + CH3COCH2COOCH3 Methyl acetoacetate HC NO2 C COOCH3 COCH3 Methyl-[2-acetyl-3-(2-nitropheny)]-2- propionate
NIFEDIPINE Step 2: preparation Methyl 3-amino 2-butenoate C H 3 C O C H 2 C O O C H 3 M e t h y l a c e t o a c e t a t e H 3 C C O H C H C O O C H 3 ( E n o l f o r m ) + N H 3 H 3 C C N H 2 C H C O O C H 3 M e t h y l 3 - a m i n o 2 - b u t e n o a t e - H 2 O
NIFEDIPINE Step 3: condensation of step 1 and step 2 product HC NO2 C COOCH3 COCH3 Methyl-[2-acetyl-3-(2-nitropheny)]-2-propionate H3C C NH2 CHCOOCH3 Methyl 3-amino 2-butenoate + NO2 H NH3C CH3 H3COOC COOCH3 Nifedipine -H2O Cyclisation
DIPYRIDAMOLE Dipyridamole is chemically 2,2,2,2-[(4,8-di- 1piperidinylpyrimido[5,4-d]pyrimidine-2,6-diyl)dinitrilo]- tetrakisethanol (Persantine), N N N N N N N CH2CH2OH CH2CH2OH N CH2CH2OH HOH2CH2C
DIPYRIDAMOLE Properties o It is bitter, yellow crystalline powder, soluble in dilute acids, methanol and chloroform o A formulation containing dipyridamole and aspirin (Aggrenox) is currently being marketed as an antithromobotic.
DIPYRIDAMOLE Pharmacological actions : o Dipyridamole is a long-acting vasodilator. Its vasodilating action is selective for the coronary system. o The drug also inhibits adenosine deaminase in erythrocytes and interferes with the uptake of the vasodilator adenosine by erythrocytes. These actions potentiate the effect of prostacyclin (PGI2), which acts as an inhibitor to platelet aggregation.
DIPYRIDAMOLE Side effect More common: Abdominal or stomach cramps, diarrhea, dizziness or lightheadedness Less common: Flushing, headache, nausea or vomiting, weakness Rare General discomfort and/or unusual tiredness or weakness, hair loss, joint pain or swelling, muscle pain, runny nose, sneezing
Calcium antagonists.pptx 1