Lidocaine

Question 1

Mechanism of action?

Answer 1

Lidocaine enters the cell in its unchanged form, it accepts a proton inside the cell to become positively charged, it then blocks voltage gated Na channels which normally initiate &propagate the action potential. Preventing the initiating &propagation of action potentials in the nerves &muscles induces local anethesia in the area supplied by these blocked nerves.
In the heart, Lidocaine reduces the duration of action potential, slows down the conduction velocity &increases the refractory period. All falls in the purpose of successfully treating ventricular fibrillation/ventricular tachycardia.

Question 2

What in the refractory period (in the heart)?

Answer 2

After an action potential initiates, the cardiac cell is unable to initiate another action potential for some duration of time (which is slightly shorter than the “true” action potential duration). This period of time is referred to as the refractory period, which is 250ms in duration and helps to protect the heart.

Question 3

Indications of Lidocaine ?

Answer 3

Local anesthetic (particularly in urinary catheterisiation &minor procedures)
Uncommonly, prescribed as antiarrhythmic for treating VT &VF.

Question 4

Indications of Lidocaine ?

Answer 4

Stinging sensations (quickly disappears). When systemically administered; neurologically : dowsiness, restlessness, tremors &fits. it generates little cardiovascular toxicity, but in overdoses it may cause arrhythmias &hypotension.

Question 5

For anesthesia indications, usually co-administered with what drug &for what purpose?

Answer 5

with Adrenaline, serving as local vasoconstrictor, to prolong the duration action of anesthesia.