Question

What are the pharmacokinetics of Lidocaine Hydrochloride?

What are the pharmacodynamics of Lidocaine Hydrochloride?

Answer 1

Pharmacokinetics:

Lignocaine is rapidly absorbed from mucous mebranes and abraded areas. Rate of absoption depends on the blood flow to the area of application. Orally, it has high first pass metabolism. Absorption from intact skin is minimal. When injected, starts action in 4 minutes.

Since it is lipophillic, it is widely distribued. Rapidly enters highely perfused organs like brain, heart, liver, kidney etc. In plasma, it is bound to alpha-1 acid glycoprotein.

Degraded in liver microsomes by dealkylation and hydrolysis. Metabolism is hence hepatic blood flow dependent.

Pharmacodynamics:

Mechanism of action:

Act by blocking Na+ ion entry, leading to decrease in rate of rise of action potential and maximum depolarisation. This leads to nerve block. It does this by interacting with voltage gated Na+ ion channel

Systemic actions:

CNS- stimulation followed by depression. Early sign of toxicity is circumoral numbness, abnormal sensation in tongue and drowsiness.

CVS: Heart- cardiac depressent- antiarrhythmic action..has mild proarrhythmic action as well.

Blood vessels: Sympathetic blockade can lead to vasodilation and fall in BP