NICARDIPINE

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Nicardipine is a dihydropyridine calcium channel blocker that selectively inhibits the influx of calcium ions into smooth muscle cells, resulting in vasodilation and reduced systemic vascular resistance. While its primary use is in the management of hypertension and angina, it also has important roles in the context of anesthesia:

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1. Intraoperative blood pressure control: During surgery, maintaining stable blood pressure is essential for patient safety and optimal surgical outcomes. Nicardipine, with its vasodilatory effects, can be used to manage intraoperative hypertension and achieve desired blood pressure targets.

2. Controlled hypotension: In certain surgical procedures, such as neurosurgery or orthopedic surgery, deliberate hypotension (lowering of blood pressure) may be employed to reduce bleeding and improve visibility in the surgical field. Nicardipine can be used to achieve controlled hypotension in a safe and reversible manner.

3. Management of hypertensive emergencies: In rare cases, patients may develop hypertensive emergencies during the perioperative period, which require rapid blood pressure reduction to prevent end-organ damage. Nicardipine, with its rapid onset and short half-life, can be administered intravenously to quickly lower blood pressure in these situations.

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Here are the main steps in nicardipine's mechanism of action:

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1. Binding to L-type calcium channels: Nicardipine selectively binds to the α1-subunit of L-type calcium channels, which are found predominantly in the smooth muscle cells of blood vessels, particularly in arterioles.

2. Inhibition of calcium influx: By binding to L-type calcium channels, nicardipine inhibits the influx of extracellular calcium ions into the vascular smooth muscle cells during membrane depolarization.

3. Decreased intracellular calcium levels: The inhibition of calcium influx leads to a decrease in intracellular calcium levels in the vascular smooth muscle cells.

4. Smooth muscle relaxation: Lower intracellular calcium levels result in relaxation of the vascular smooth muscle, causing vasodilation, particularly in the arterial system.

5. Decreased systemic vascular resistance and blood pressure: As the arterioles dilate, systemic vascular resistance decreases, leading to a reduction in blood pressure.

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                                                                                         Key points about Nicardipine

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• The dihydropyridines prevent calcium entry into the vascular smooth cells by extracellular allosteric modulation of the L-type voltage-gated calcium channels.

 

• The primary affinity of the dihydropyridines such as nicardipine is for the peripheral arterioles.

 

• Nicardipine lacks effects on the sinoatrial node and atrioventricular node.

 

• It has minimal myocardial depressant effects.

 

• It has the greatest vasodilating effects of all the calcium entry blockers.

 

• Vasodilation is prominent in the coronary arteries.

 

• Side effects include flushing, vertigo, and headache.

 

• Reflex tachycardia attributed to sympathetic nervous activity and baroreceptor reflex may be observed with administration.

 

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