Calcium Channel Blockers Drugs

                        Calcium channel blockers (CCBs)

Introduction: We know that muscles use calcium for contraction. We have three type of muscles they are skeletal muscles, smooth muscles and cardiac muscles. Skeletal muscles use calcium of sarcoplasmic reticulum for contraction while cardiac and smooth muscles use calcium use calcium from extracellular fluid for contraction. When the calcium entry is blocked then contraction will be of limited value or no more and relaxation occur. CCBs do this and inhibit voltage gated calcium channels and prevent calcium entry to the muscles cells.  They exclusively act on ligend gated calcium channels or shortly called as L-type ca channels. 

Chemically classification of CCBs

1 )   Dihydropyridines)

 Drugs included are Nifidipine,  Amlodipine, Nimodipine, Felodipine,Nicardipine.  Dihydropyridines are Vaso-Selective mean they act on blood vessels and dilate them by blocking calcium channels there.

2)       Phenylalkylamines

Drugs included are Verapamil just only on drug. Verapamil is cardio selective and act just on heart calcium channels. No vessel calcium channel blockage so no effect there.

3 ) Benzothizipenes  one important in this class drug is Deltiazem. Deltiazem is both veso and cardio selective.

                         Mechanism of action of CCBs

As mentioned above that CCBs block voltage gated calcium channel and prevent entry of calcium to the cell. In voltage gated calcium channel they further block, L-type voltage gated calcium channel. All the CCBs binds with channel from the inside of the cell and bind to alpha sub unit of the channel. Nifidipine and its fellows bind with different section of alpha unit while verapamil and Dltiazem binds with another section and thus prevent the entry of calcium to the muscles cell. Verapamil is cardio selective and only act at cardiac muscles Nifidipine and its family act on smooth muscles. While Deltiazem is in between show some action on heart and at the same time on the smooth muscles as well.

                                                   USES 

Angina pectoris Nifidipine and fellows dilate vessels and thus increase blood flow to the heart and used in angina. At the same time verapamil reduces heart contraction on the heart and thus reduces heart load so used in angina.

Hypertension (HTN) Nifidipene and fellows used in HTN because they reduces the vascular tone and reduces blood pressure. At the other hand verapamil reduces cardiac output and treat HTN. Deltiazem reduces vesular tone and reduces heart load so blood pressure is lowered.

Tachyarrhythmia verapamil and deltiazem is use because they act on SA and AV node and suppress them so the firing from SA and AV node reduces and calcium blockage also reduces the conduction of velocity so thus reduces heart rate and arrhythmia is treated. Nifidipine is of no use in this case because it has no effect on heart.