benzocaine (CA-1? question)

[Dr Acula]

Why does benzocaine work so well on mucosal surfaces - why not lidocaine or ....?

I've got the Mechanism of Action:
Ester local anesthetic blocks both the initiation and conduction of nerve impulses by decreasing the neuronal membrane's permeability to sodium ions, which results in inhibition of depolarization with resultant blockade of conduction

BUT why is the absorption "poor to intact skin" but "well absorbed from mucous membranes and traumatized skin"

anyone? anyone?

DA

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[huktonfonix]

who said lidocaine doesn't work well on mucosal surfaces? We use it all the time for awake fiberoptics, so it works just fine. As far as the absorption from different surfaces, it will absorb through skin it just takes higher concentrations and looooong waiting periods (i.e. EMLA) . I believe it just takes longer to penetrate the keratinized epithelium which wont be present or will be compromised in broken skin and mucous membranes. As far as differences for onset times, its all about the pKa and lipid solubility and concentration of the local.

 

[Dr Acula]

who said lidocaine doesn't work well on mucosal surfaces? We use it all the time for awake fiberoptics, so it works just fine. As far as the absorption from different surfaces, it will absorb through skin it just takes higher concentrations and looooong waiting periods (i.e. EMLA) . I believe it just takes longer to penetrate the keratinized epithelium which wont be present or will be compromised in broken skin and mucous membranes. As far as differences for onset times, its all about the pKa and lipid solubility and concentration of the local.

thanks for the reply ...

yeah, we talked about pKa, keratinized epithelium and lipid sol but Mr. smarty-pants attending said "No, find me the answer." And I still really have no idea - receptors present on mucosa? more base avail? (but wouldn't that be pKa?) ...