Acids, Bases, and Buffers Flashcards
Why would an infected tissue site decrease the effectiveness of a LA?
The tissue is more acidic. The percent of ionized drug is increased
What is LeChatlier’s Principle?
When a system in dynamic equilibrium is disturbed, it will react to reestablish the equilibrium condition.
What is an example of LeChatlier’s Principle in the body?
Hemoglobin binding reversibly to oxygen.
What does K stand for in chemical reactions?
The equilibrium constant.
If K is increased, does the reaction tend to favor products or starting materials?
Products.
What is an example of a shift in K in the body?
O2/Hgb dissociation curve.
If K is followed by the subscript “a”, what does this denote?
Ka is for weak acids.
If you add products, what happens to the equilibrium?
Shifts toward reactants.
If you remove products, what happens to the equilibrium?
Shift toward products.
What is the Bronstead definition of an acid? Base?
An acid is a proton donor.
A base is a proton acceptor.
When an acid donates a proton, what is it converted to?
Conjugate base
Ex: HA» (H+) + (A-).
The A- is the conjugate base.
When an base accepts a proton, what is it converted to?
Conjugate Acid.
Ex: B + H+» BH+
What is an example of a conjugate acid-base pair?
HCl
What is an example of an amphoteric species?
H2O
What is an amphoteric specie?
Can behave as either an acid or base
T/F: The Stronger the acid, the stronger the conjugate base?
False:
Stronger the acid, the weaker the conjugate base.
What pH defines an acidic solution? Basic solution?
<7
>7
T/F: Weak acids establish an equilibrium?
True
Do ionized or nonionized drugs readily penetrate the blood brain and placental barrier?
Nonionized=lipid soluble.
The ionized form of a drug is said to be water or lipid soluble?
Water soluble.
What are the 3 steps of determining drug effectiveness?
- Is the drug a weak acid or weak base.
- What is the pKa of the drug.
- The pH of the target solution (tissue/blood/etc).
Acid+acid= ionized or nonionized?
Nonionized.
What are examples of salt drugs?
Sodium, calcium, or magnesium , chloride, sulfate drugs.
Are salt drugs considered a weak acid or weak base?
Weak acid if is sodium, calcium, magnesium (Positive charge)
Weak base if Chloride or sulfate (negative charge)
Base+Acid= ionized or nonionized?
Ionized
Describe pKa?
The pH at which 50% of the drug is ionized and 50% of the drug is nonionized.
Why would trapping of local anesthetics happen in fetal circulation?
Fetus pH is less than maternal. Circulating nonionized drug crosses the placental barrier. Once crossed, equilibrium reestablishes and greater % ionized and trapped.
