These are calcium entry blockers. Its major effect is seen in vascular smooth muscle and the heart.
Action:
It reduces the influx of calcium leading to reduced rate of Phase 4 (spontaneous depolarization).
It also causes a reduction of conduction in those tissues which are dependent on calcium flow i.e. AV node.
Sunday, March 6, 2011
Dofetilide
Pharmacokinetics:
Its half life is about 10 hours. It is excreted in urine.
Therapeutic uses:
1. First line agent in sustained atrial fibrillation. Alongwith, amiodarone and β-blocking agents it is mostly used for atrial fibrillation.
2. In coronary disease of artery when left ventricular function is disturbed.
Its half life is about 10 hours. It is excreted in urine.
Therapeutic uses:
1. First line agent in sustained atrial fibrillation. Alongwith, amiodarone and β-blocking agents it is mostly used for atrial fibrillation.
2. In coronary disease of artery when left ventricular function is disturbed.
Sotalol
It also has a potent non-selective β-blocking agent.
As indicative of β-blocking agents, it also has the ability of decreasing mortality from acute myocardial infarction.
Actions:
It causes the inhibition of potassium outflow (also referred to as delayed rectifier). This inhibition increases both
1. Repolarization and
2. Action potential duration
And have the ability of prolonging the effective refractory period.
It has the ability of suppressing the ectopic beats and decreases myocardial oxygen demand. In the case of myocardial ischemia, it has prominent anti-fibrillatory affect.
Therapeutic uses:
1. Myocardial Ischemia
2. Sustained ventricular tachycardia
Adverse effects:
Prolonging the QT interval leading to torsade de pointes syndrome.
As indicative of β-blocking agents, it also has the ability of decreasing mortality from acute myocardial infarction.
Actions:
It causes the inhibition of potassium outflow (also referred to as delayed rectifier). This inhibition increases both
1. Repolarization and
2. Action potential duration
And have the ability of prolonging the effective refractory period.
It has the ability of suppressing the ectopic beats and decreases myocardial oxygen demand. In the case of myocardial ischemia, it has prominent anti-fibrillatory affect.
Therapeutic uses:
1. Myocardial Ischemia
2. Sustained ventricular tachycardia
Adverse effects:
Prolonging the QT interval leading to torsade de pointes syndrome.
Class III Antiarrhythmic Drugs
These are potassium channel blockers.
Actions:
They reduce the outward flow of potassium during repolarization phase of cardiac cells.
They have the ability of increasing the duration of action potential without changing Phase 0 of depolarization or the resting membrane potential.
They also have the ability of prolonging the effective refractory period.
Class III antiarrhythmic agents have the potential of induction of arrhythmias.
Actions:
They reduce the outward flow of potassium during repolarization phase of cardiac cells.
They have the ability of increasing the duration of action potential without changing Phase 0 of depolarization or the resting membrane potential.
They also have the ability of prolonging the effective refractory period.
Class III antiarrhythmic agents have the potential of induction of arrhythmias.
Esmolol
It is one of the very short acting β-blocker.
Therapeutic uses:
It is used intravenously in acute arrhythmias that occur in surgical and emergency situations.
Therapeutic uses:
It is used intravenously in acute arrhythmias that occur in surgical and emergency situations.
Metoprolol
It is selective β1 blocker.
Therapeutic uses:
1. Hypertension
2. Angina pectoris (increase endurance to exercise)
Safe in patients with diabetes or peripheral vascular disease. It decreases the risk of bronchospasm.
Therapeutic uses:
1. Hypertension
2. Angina pectoris (increase endurance to exercise)
Safe in patients with diabetes or peripheral vascular disease. It decreases the risk of bronchospasm.
Bretylium
Mechanism of action:
1. It is an adrenergic neuronal blocking agent. It is collected in adrenergic nerve terminals, where it stimulates norepinephrine release firstly but then causes inhibition of the release of norepinephrine in response to neuronal stimulation.
2. It also has direct electrophysiologic effects on heart.
Actions:
1. Promoted duration of ventricular action potential and effective refractory period is more pronounced in ischemic cells.
2. It also causes an increase of action potential duration and effective refractory period of atrial muscle and AV node.
3. Some positive inotropic effect is also observed from initial release of norepinephrine.
Therapeutic uses:
It is used for those life threatening ventricular arrhythmias which are unresponsive to other therapy.
Adverse effects:
Orthostatic hypotension (adrenergic neuron blocking mechanism), Nausea, vomiting
1. It is an adrenergic neuronal blocking agent. It is collected in adrenergic nerve terminals, where it stimulates norepinephrine release firstly but then causes inhibition of the release of norepinephrine in response to neuronal stimulation.
2. It also has direct electrophysiologic effects on heart.
Actions:
1. Promoted duration of ventricular action potential and effective refractory period is more pronounced in ischemic cells.
2. It also causes an increase of action potential duration and effective refractory period of atrial muscle and AV node.
3. Some positive inotropic effect is also observed from initial release of norepinephrine.
Therapeutic uses:
It is used for those life threatening ventricular arrhythmias which are unresponsive to other therapy.
Adverse effects:
Orthostatic hypotension (adrenergic neuron blocking mechanism), Nausea, vomiting
Subscribe to:
Posts (Atom)
-
Q: What do you know about ergot alkaloids? Ans: These include alkaloids which we get from the ergot fungus Claviceps purpurea or derived ...
-
(For detailed study of Pharmaceutical Incompatibility Click here) Multiple Choice Questions (MCQs) from Pharmaceutical Incompatibility in ...
-
Multiple Choice Questions (MCQs) of Powders and Granules from Pharmaceutics 1. _______ powders consist of more than one ingredients. a. Si...
