Respecto del efecto del pH en la acción de los anestésicos locales
Mario Rivera M. 21 Nov 202321/11/23 a las 18:18 hrs.2023-11-21 18:18:21
Les adjunto este parrafo del Rnag and Dale respecto del efecto del pH en la acción de los AL:
"Local anaesthetic activity is strongly pH-dependent, being increased at alkaline extracellular pH (i.e. when the proportion of ionised
molecules is low) and reduced at acid pH. This is because the compound needs to penetrate the nerve sheath and the axon membrane to reach the inner end of the sodium channel (where the local anaesthetic-binding site resides). Because the ionised form is not membrane-permeant, penetration is very poor at acid pH. Once inside the axon, it is primarily the ionised form of the local anaesthetic molecule that binds to the channel and blocks it (Fig. 44.2), the unionised form having only weak channel-blocking activity. This pH dependence can be clinically important, because the extracellular fluid of inflamed tissues is often relatively acidic and such tissues are thus somewhat resistant to local anaesthetic agents".
En resumen paa queue el AL llegue al sitio de acción y penetre en el axon debe estar no ionizado. Una vez en el canal de sodio es la forma ionizada, cuya abundancia dependerá del pKa del fármaco, la que se une al canal y lo bloquea.
espero quede mas claro con esta explicación.
Saludos,
Mario Rivera
"Local anaesthetic activity is strongly pH-dependent, being increased at alkaline extracellular pH (i.e. when the proportion of ionised
molecules is low) and reduced at acid pH. This is because the compound needs to penetrate the nerve sheath and the axon membrane to reach the inner end of the sodium channel (where the local anaesthetic-binding site resides). Because the ionised form is not membrane-permeant, penetration is very poor at acid pH. Once inside the axon, it is primarily the ionised form of the local anaesthetic molecule that binds to the channel and blocks it (Fig. 44.2), the unionised form having only weak channel-blocking activity. This pH dependence can be clinically important, because the extracellular fluid of inflamed tissues is often relatively acidic and such tissues are thus somewhat resistant to local anaesthetic agents".
En resumen paa queue el AL llegue al sitio de acción y penetre en el axon debe estar no ionizado. Una vez en el canal de sodio es la forma ionizada, cuya abundancia dependerá del pKa del fármaco, la que se une al canal y lo bloquea.
espero quede mas claro con esta explicación.
Saludos,
Mario Rivera
| Última Modificación | 21 Nov 202321/11/23 a las 18:18 hrs.2023-11-21 18:18:21 |
|---|---|
| Vistas Únicas | 103 |
| Compartir |
