Pretend you are a teacher preparing a quiz for the text I will provide. 
            Each quiz question should follow the format below. 
            Ensure that you carefully recheck the questions and answers for accuracy. 
            The output should be a ready-to-use list of dictionaries for the Python eval function:

            [

                    "question": "WRITE THE QUESTION HERE",
                    "options": ["A) OPTION_1", "B) OPTION_2", "C) OPTION_3", "D) OPTION_4"],
                    "answer": INDEX_OF_CORRECT_ANSWER_IN_OPTIONS_LIST,
                    "explanation": "EXPLAIN WHY THE ANSWER IS CORRECT"

            ]

            Text:
             
● Dispensed as acid salts, mostly the hydrochloride salt (e.g., lidocaine hydrochloride, 
articaine hydrochloride). 
● Dissolved in sterile water or saline. 
2 factors that greatly influence the nerve blocking action:  
 
1. PH of tissues:  
● Acidification of tissue decreases local anesthetic effectiveness, therefore failure of 
anesthesia in areas of infection or inflammation.  
● PH of normal tissues: 7.4  
● PH of inflamed area: 5 to 6 
 
2. PH of LA:     
● PH of plain LA: about 6.5  
● PH of LA with epinephrine: about 3.5 to 4.4.  
● Clinically this lower PH would cause:  
1. Burning sensation on injection. 
2. Slightly slower onset of anesthesia. 
3. More post injection soreness at the site of drug administration. 
● Alkalinization of LA:  
1. Speeds up onset of action.  
2. Increases its clinical effectiveness.  
3. More comfortable on injection.  
Because of the unstableness of the LA base, it precipitates out of the alkalinized solutions making 
it unsuitable for clinical use so —> Buffered local anesthetics are now used  
 
● Sodium bicarbonate or carbon dioxide (CO2) (less common) added to provide:  
1. Greater comfort 
2. More rapid onset of anesthesia. 
Dissociation of Local Anesthetics 
● Acid salts of LA exist in the solution prepared as:  
1. Uncharged molecules (RN) (called base)  
2. Positively charged molecules (RNH+) (called cation) 
3. Hydrogen ions (H+) (since the PH of the solution is acidic) 
 
Relative proportion of each 
ionic form  
In case of high concentration 
of hydrogen ions (low pH) 
In case of low hydrogen ion 
concentration (higher pH) 
RNH+ ⇌RN+H+ 
RNH+ >RN+H+ 
equilibrium shifts to  cationic 
form 
RNH+ <RN+H+ 
equilibrium shifts toward the 
free base form 
 
● The relative proportion of ionic forms also depends on the pKa  
● The pKa of a local anesthetic determines its speed of action.  
● The pKa of a local anesthetic is the pH at which equal concentrations of ionized and un-
ionized forms exist (50-50 %).  
● The closer the pKa of a local anesthetic is to the pH of tissue (7.4), the more rapid the onset 
due to the greater amount of un-ionized agent available for diffusion 
Actions on Nerve Membranes 
 
The two factors involved in the action of a local anesthetic are:  
1. Diffusion of the drug through the nerve sheath (diffusibility) by free form (RN). 
2. Binding at the receptor site in the ion channel (binding).  
From the axoplasmic side:  
● RNH+ ions enter sodium channels. 
● Binding to the channel receptor site. 
● Ultimately resulting in conduction blockade. 
 
 
 
At PH 7.4:  
1. LA with high pKa value (e.g., procaine, with a pKa of 9.1) has very few molecules 
available in the RN form to diffuse through the nerve membrane. This Slows the onset of 
anesthesia of this drug.  
2.   LA with a lower pKa (e.g., lidocaine, pKa 7.7) has a greater number of lipophilic free 
base molecules available to diffuse through the nerve sheath. However, the anesthetic 
action of this drug is inadequate because a

            Quiz: