Ionization Of Drugs Flashcards
When something is non-ionized, what does this mean?
It is not charged
When something is ionized, what does this mean?
It is charged
Which drugs cross the membrane easier, ionized or non-ionized?
Non-ionized (uncharged)
In regards to acids and bases, what are most drugs?
Weak acids or weak bases
If you have a drug that is either a weak acid or a weak base, what can happen to it?
It can be ionized (influenced by pH)
If you have a hydrogen attached to an acid, what form is it in?
Non-ionized (no charges)
If you have an acid with no hydrogen attached to it, what form is it in?
Ionized (charged)
If you have a hydrogen attached to a base, what form is it in?
Ionized (charged)
If you have a base with no hydrogen attached to it, what form is it in?
Non-ionized (no charges)
In what type of pH environments are there lots of hydrogens?
Low pH (acidic)
Constant pH for a drug, where 50% is ionized and 50% is non-ionized
pKa
Where do you draw the divider line in order to see pKa?
Right down the arrows dividing the 2 sides of the equations
If you have a drug that is HA, in what type of pH environment will it be in?
Acidic (lots of hydrogens want to bind to the weak acid)
Using the terms relatively loosely, what does the term basic mean?
Above the drugs pKa
Using the terms relatively loosely, what does the term acidic mean?
Below the drug’s pKa
Which forms of the acid and base will penetrate the cell membrane?
HA (uncharged weak acid)
B (uncharged weak base)
Which forms of the acid and base will not penetrate the cell membrane?
A- (charged weak acid)
BH+ (charged weak base)
The lower the pKa, the stronger the _____?
Acid
The higher the pKa, the stronger the _____?
Base
Example:
Here’s a drug who’s a weak acid, and it’s pKa is 5.0. If the drug is placed in a pH of 7.0, the major form of this drug is what?
A- (charged, ionized, weak acid)
Because the pH is greater than the pKa, it will be on the basic side of things.
Example:
Here’s a drug who’s a weak acid, and it’s pKa is 5.0. If the drug is placed in a pH of 7.0, the major form of this drug is A- (charged, ionized, weak acid). Is this drug going to easily move in the body?
No because it is charged and cannot pass the membrane
What is the equation for Henderson-Hasselbalch?
pH - pKa
Using the H-H equation, if you receive a negative number, what does this mean?
pH is less than pKa, meaning it is in an acidic environment
Using the H-H equation, if you receive a positive number, what does this mean?
pH is greater than pKa, meaning it is in a basic environment
Which form of weak acid easily passes the membrane?
HA
Which form of weak base easily passes the membrane?
B
What kind of solubility does a non-ionized (NI) drug have? What does this mean for the drug?
Lipid soluble
-this is why it moves easily in the body (wants to stay b/c it can move through the cell membrane)
What kind of solubility does an ionized (I) drug have? What does this mean for the drug?
Water soluble
-more readily eliminated form the body because it can not pass the cell membrane
Given an acid and a base, what forms are non-ionized?
HA and B
Given an acid and a base, what forms are ionized?
A- and BH+
Since pH is on a log scale, if you change pH by just 1 unit, how much are you changing the concentration of the drug?
By 10-fold
If pH is less than pKa, what environment are you in?
Acid, relative to drug’s pKa
If pH is greater than pKa, what environment are you in?
Basic, relative to drug’s pKa
In a low pH environment, what would you expect to be the percent of non-ionized acid and base, and in which form?
HA = very high BH+ = very low
In a high pH environment, what would you expect to be the percent of non-ionized acid and base, and in which form?
A- = very low B = very high
Where the acid and base curves cross, what does it mean?
pH = pKa (50% ionized and 50% non-ionized)
If you give a weak acid drug to a patient, where in their body will it absorb best?
Stomach (pH = 1)
If you give a weak base drug to a patient, where in their body will it absorb best?
Small intestines (pH = 5-6)
What is the pH of blood?
7.4
What is the pH of urine?
5-8
What is the pH of the stomach?
1
What is the pH of the small intestines?
5-6
Which forms of acids and bases will have a greater clearance (will be more easily cleared from the body)?
Ionized (charged) forms like HB+ and A-
To get rid of a weak acid, what type of environment would you want to put it it?
Basic solution (closer to 8)
To get rid of a weak base, what type of environment would you want to put it it?
Acidic solution (closer to 5)
When pH is less than pKa, what forms of acid and base predominate, and are the protonated or deprotonated?
Protonated
HA and BH+
When pH is greater than pKa, what forms of acid and base predominate, and are the protonated or deprotonated?
Deprotonated
A- and B
Where will a drug go if you put it in it’s “like” environment? (Acid in an acidic environment)
It will stay in that environment
Where will a drug go if you put it in it’s “un-like” environment? (Acid in a basic environment)
It will leave that environment
If a patient has over-dosed on weak acid, what do you do for that patient?
Give them a fixed amount of sodium bicarb to manipulate the urine to make it closer to 8 (more alkaline) in order to get rid of the acid
If a patient has over-dosed on weak base, what do you do for that patient?
Give them a fixed amount of ammonium chloride to manipulate the urine to make it closer to 5 (more acidic) in order to get rid of the base
What drug do you use to treat hepatic enchephalopathy?
Lactulose
What is lactulose converted to by the gut bacteria, when trying to treat hepatic encephalopathy?
Lactic acid
When treating hepatic encephalopathy with lactulose, the acidic environment in the gut converts what to what?
In converts ammonia (NH3) to ammonium (NH4+)
Why do you give a patient with hepatic encephalopathy lactulose?
The gut bacteria converts the intestinal tract to be acidic, so NH3 (ammonia) is converted into NH4+ (ammonium), which has a positive charge (ionized), meaning it is more easily eliminated from the body
