1question part 2

[krasnodar]

1. if you are increase the pKa of LA solution What will it do :

ONSET OF ACTION DURATION

a) legthen legthen
b)legthen shorten
c) shorten lengthen
d)shorten shorten

explain PLEASE

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[myra1972]

1. if you are increase the pKa of LA solution What will it do :

ONSET OF ACTION DURATION

a) legthen legthen
b)legthen shorten
c) shorten lengthen
d)shorten shorten

explain PLEASE

I think it both lengthen the onset of action and duration. I've read it somewhere.

 

[krasnodar]

the percentage of spcific LA which is present in the base when injected into tissue whose PH is 7.4 is inversely proportional to pKa of that agent

a onset is faster , duration is longer
b onset is slower , duration is longer
c onset is the same , duration is the same
d onset is slower duration is the same

 

[maaidabd]

the percentage of spcific LA which is present in the base when injected into tissue whose PH is 7.4 is inversely proportional to pKa of that agent

a onset is faster , duration is longer
b onset is slower , duration is longer
c onset is the same , duration is the same
d onset is slower duration is the same

According to what i have read is that pka is the ph at 50% of local anaesthesia exist in charged & 50% exist in uncharged form.so if u lower the pka the more is the unionised free base form= more easily cross the lipid nerve memb=faster onset of action
however i didn,t find the relationship of pka to the duration of action, everywhere it says more protein binding(Na channel) of local anaesthsia, the more is the duration.
anyone with the diffrent idea?

 

[dentidoc]

1. if you are increase the pKa of LA solution What will it do :

ONSET OF ACTION DURATION

a) legthen legthen
b)legthen shorten
c) shorten lengthen
d)shorten shorten

This is what i think; If the Pka is increased the unionised free base form available for penetration will be less, hence the onst of action will be delayed, but duration of an anesthesia will be increased.
so the answer shle be (b)
Let me know if there is sum other explanation fr this.
thanks