The answer is C. slower onset of action.

Here's why:

Lidocaine is a weak base with a pKa of 7.9. In its charged form (R3NH+), it is water-soluble and unable to cross cell membranes, while in its uncharged form (R3N), it is lipid-soluble and can cross cell membranes.

At a pH of 7.4 (physiological pH), most of the lidocaine is in its uncharged form and can readily cross cell membranes to exert its anesthetic effect. However, when the pH is lowered to 6.5 (as in infected tissue), more of the lidocaine is in its charged form and cannot cross cell membranes as easily. This results in a slower onset of action.

A. The [R3N]/[R3NH+] ratio would be lower, not higher, because more lidocaine is in its charged form.

B. The duration of action would not necessarily be increased. While the lidocaine may take longer to start working, this does not mean it will work for a longer period of time.

D. The diffusion rate of R3NH+ across the membrane would be decreased, not increased, because the charged form of lidocaine cannot cross cell membranes as easily as the uncharged form.

Question

The answer is C. slower onset of action.

Here's why:

Lidocaine is a weak base with a pKa of 7.9. In its charged form (R3NH+), it is water-soluble and unable to cross cell membranes, while in its uncharged form (R3N), it is lipid-soluble and can cross cell membranes.

At a pH of 7.4 (physiological pH), most of the lidocaine is in its uncharged form and can readily cross cell membranes to exert its anesthetic effect. However, when the pH is lowered to 6.5 (as in infected tissue), more of the lidocaine is in its charged form and cannot cross cell membranes as easily. This results in a slower onset of action.

A. The [R3N]/[R3NH+] ratio would be lower, not higher, because more lidocaine is in its charged form.

B. The duration of action would not necessarily be increased. While the lidocaine may take longer to start working, this does not mean it will work for a longer period of time.

D. The diffusion rate of R3NH+ across the membrane would be decreased, not increased, because the charged form of lidocaine cannot cross cell membranes as easily as the uncharged form.

Knowee AI · Accepted Answer

The answer is C. slower onset of action.

Here's why:

Lidocaine is a weak base with a pKa of 7.9. In its charged form (R3NH+), it is water-soluble and unable to cross cell membranes, while in its uncharged form (R3N), it is lipid-soluble and can cross cell membranes.

At a pH of 7.4 (physiological pH), most of the lidocaine is in its uncharged form and can readily cross cell membranes to exert its anesthetic effect. However, when the pH is lowered to 6.5 (as in infected tissue), more of the lidocaine is in its charged form and cannot cross cell membranes as easily. This results in a slower onset of action.

A. The [R3N]/[R3NH+] ratio would be lower, not higher, because more lidocaine is in its charged form.

B. The duration of action would not necessarily be increased. While the lidocaine may take longer to start working, this does not mean it will work for a longer period of time.

D. The diffusion rate of R3NH+ across the membrane would be decreased, not increased, because the charged form of lidocaine cannot cross cell membranes as easily as the uncharged form.

Lidocaine is injected into infected tissue with a pH of 6.5. At the injection site, one would expect:A.higher [R3N]/[R3NH+] ratioB.increased duration of actionC.slower onset of actionD.increased R3NH+ diffusion rate across the membrane

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