qs 10 - okt3

[ArchivalUser]

A 32-year-old woman presents to the emergency room with a laceration on the palm of her hand after accidentally cutting herself while chopping vegetables. The medical student on service is asked to clean and suture the wound. After thorough irrigation, lidocaine is injected around the wound to provide local anesthesia. Which of the following is true regarding lidocaine?

A.Lidocaine blocks potassium channels
B.Lidocaine exists in cationic form at a low pH.
C.Lidocaine binds extracellular receptors
D.Lidocaine is an ester anesthetic
E.Lidocaine is a weak acid

[ArchivalUser]

B?

[ArchivalUser]

bbbb

[ArchivalUser]

its a weak acid: ? ans :E

[ArchivalUser]

Choice (B) the correct answer. Local anesthetics are weak bases that have a pKa in the 8-9 range. At acidic pHs, local anesthetics exist in ionized or cationic form and penetrate cellular membranes less efficiently. The non-ionized form of local anesthetics crosses cellular membranes and binds intracellular membrane receptors in ionized form and results in sodium channel blockade. This disrupts nerve conduction and results in anesthesia at the site of injection. Lidocaine is a local anesthetic that belongs to the amide group of local anesthetics. The other choices are incorrect.