Study Set Content:
Increase in pKA=
weak acid
Increase in pKA=
strong base
Accordingly, most weak acid drugs are predominantly in
the (blank) from at lower pH of the gastric fluid and,
therefore are absorbed from the stomach as well as from
the intestine.
un-ionized
Some very weak acidic drugs, such as phenytoin and many
barbiturates, the pKA values of which are greater than (blank)
are essentially un-ionized at all pH values.
8.0
Therefore, for these weak acid drugs, transport is more
rapid and(blank) provided that the un-ionized
form is lipophilic or non polar.
independent of pH,
Furthermore, it is important to note that the fraction un-
ionized changes dramatically only for weak acids with pKA
values between
3 and 7.
Influences the transport and absorption
processes of drugs and it is one of the most
widely used properties in quantitative structure-
activity relationships.
PARTITION COEFFICIENT
Measure of the relative affinities of the solute for
an
aqueous or non- aqueous or oil phase.
The movement of molecules from one phase to
another is called
partitioning.
Drugs partition themselves between the
aqueous phase and lipophilic membrane.
The greater the value of Partition
coefficient, the (blank) the lipid solubility
of the solute.
higher
The availability of the drug molecule in a solution form is pre
requisite for drug absorption and the biologic fluids at the site of
absorption are (blank) in nature.
aqueous
Therefore, drugs must exhibit a balance between
hydrophilicity and
lipophilicity.
Examples of polar of hydrophilic molecules that are poorly absorbed
following oral administration and, therefore, must be administered
parenterally include:
- Gentamicin
- Ceftriaxone
- Streptokinase
The lipid- soluble drugs with favorable partition coefficients
generally are (blank) after oral administration.
well absorbed
– High Solubility and High Permeability
CLASS I DRUGS
High Solubility and Low Permeability
CLASS III DRUGS
Low Solubility and High Permeability
CLASS II DRUGS-
Low Solubility and Low Permeability
CLASS IV DRUGS-
Refers to the placement of a drug directly into
blood, either IV or intra-arterially.
INTRAVASCULAR ADMINISTRATION
