Pharmacology

Question 1

What is lidocaine?

Answer 1

an anaesthetic (blocks sensation) with minor analgesic (pain killer) properties

Question 2

What type of drug is it?

Answer 2

Class Ib drug
 It has a fast onset.
 Shorten the action potential duration.
 Decrease refractoriness

Question 3

What are class I drugs?

Answer 3

 block voltage-sensitive (voltage-gated) sodium channels; this blockage causes a loss of sensation and eliminates the responsiveness of these cells to pain.
 bind to the sodium channels most strongly when they are in either the open or the refractory/inactive state, less strongly to channels in the resting state.
 Their action therefore shows the property of ‘use dependence’ (i.e. the more frequently the channels are activated, the greater the degree of block produced).

Question 4

What can class I agents be subdivided into?

Answer 4

 Ia: lengthen the action potential (bind to sodium channel in the open or inactive/refractory states (open state binding > refractory/inactive state binding))
 Ib: shorten the action potential (bind to sodium channel in the open or inactive/refractory states (refractory/inactive state binding&raquo_space; open state binding))
 Ic: no significant effect on the action potential (bind to sodium channel in the open state)

Question 5

What are the uses of lidocaine?

Answer 5

• Given by intravenous infusion to treat and prevent ventricular dysrhythmias in the immediate aftermath of a myocardial infarction.
• Also used as a local anaesthetic (analgesic) for minor surgery.
• Widely used for local anaesthesia (analgesic) (for needle aspirations/ chest drains).

Question 6

What’s its half-life? and how can this be affected?

Answer 6

• 2 hour half-life, increased by reducing hepatic blood flow (97% clearance in 10 hours).

Question 7

What are the side effects?

Answer 7

Side-effects – drowsiness, disorientation, convulsions, bradycardia, decreased cardiac output, vasodilation.