Acids, Bases, and Buffers

Question 1

Why would an infected tissue site decrease the effectiveness of a LA?

Answer 1

The tissue is more acidic. The percent of ionized drug is increased

Question 2

What is LeChatlier’s Principle?

Answer 2

When a system in dynamic equilibrium is disturbed, it will react to reestablish the equilibrium condition.

Question 3

What is an example of LeChatlier’s Principle in the body?

Answer 3

Hemoglobin binding reversibly to oxygen.

Question 4

What does K stand for in chemical reactions?

Answer 4

The equilibrium constant.

Question 5

If K is increased, does the reaction tend to favor products or starting materials?

Answer 5

Products.

Question 6

What is an example of a shift in K in the body?

Answer 6

O2/Hgb dissociation curve.

Question 7

If K is followed by the subscript “a”, what does this denote?

Answer 7

Ka is for weak acids.

Question 8

If you add products, what happens to the equilibrium?

Answer 8

Shifts toward reactants.

Question 9

If you remove products, what happens to the equilibrium?

Answer 9

Shift toward products.

Question 10

What is the Bronstead definition of an acid? Base?

Answer 10

An acid is a proton donor.

A base is a proton acceptor.

Question 11

When an acid donates a proton, what is it converted to?

Answer 11

Conjugate base

Ex: HA» (H+) + (A-).
The A- is the conjugate base.

Question 12

When an base accepts a proton, what is it converted to?

Answer 12

Conjugate Acid.

Ex: B + H+» BH+

Question 13

What is an example of a conjugate acid-base pair?

Answer 13

HCl

Question 14

What is an example of an amphoteric species?

Answer 14

H2O

Question 15

What is an amphoteric specie?

Answer 15

Can behave as either an acid or base

Question 16

T/F: The Stronger the acid, the stronger the conjugate base?

Answer 16

False:

Stronger the acid, the weaker the conjugate base.

Question 17

What pH defines an acidic solution? Basic solution?

Answer 17

<7

>7

Question 18

T/F: Weak acids establish an equilibrium?

Answer 18

True

Question 19

Do ionized or nonionized drugs readily penetrate the blood brain and placental barrier?

Answer 19

Nonionized=lipid soluble.

Question 20

The ionized form of a drug is said to be water or lipid soluble?

Answer 20

Water soluble.

Question 21

What are the 3 steps of determining drug effectiveness?

Answer 21

1. Is the drug a weak acid or weak base.
2. What is the pKa of the drug.
3. The pH of the target solution (tissue/blood/etc).

Question 22

Acid+acid= ionized or nonionized?

Answer 22

Nonionized.

Question 23

What are examples of salt drugs?

Answer 23

Sodium, calcium, or magnesium , chloride, sulfate drugs.

Question 24

Are salt drugs considered a weak acid or weak base?

Answer 24

Weak acid if is sodium, calcium, magnesium (Positive charge)

Weak base if Chloride or sulfate (negative charge)

Question 25

Base+Acid= ionized or nonionized?

Answer 25

Ionized

Question 26

Describe pKa?

Answer 26

The pH at which 50% of the drug is ionized and 50% of the drug is nonionized.

Question 27

Why would trapping of local anesthetics happen in fetal circulation?

Answer 27

Fetus pH is less than maternal. Circulating nonionized drug crosses the placental barrier. Once crossed, equilibrium reestablishes and greater % ionized and trapped.