unit 3 Flashcards
The biological activity of a targeted drug molecule is solely dependent on its physicochemical characteristics, essentially the ___ and ____
- NATURE AND TYPE OF FUNCTIONAL MOIETIES
- SPATIAL ARRANGEMENT
Modulating the structure of a drug implies ___,___,___ of certain groups in the drug.
INTRODUCTION
ELIMINATION
SUBSTITUTION
It plays an important role in modifying the biological activities of many compounds.
PHYSICOCHEMICAL PROPERTIES
Substances that are present at the same proportional saturation in a given medium have the same degree of biological action
FERGUSON PRINCIPLE
According to ___, it is unnecessary neither to define the nature of the biophase or the receptor nor to to measure the concentration of the drug at this site.
FERGUSON
If equilibrium conditions exist between the drug in molecular biophase and in extracellular fluids, the tendency to escape from each phase is the same, even though the concentrations in the two phases are different.
THERMODYNAMIC ACTIVITY
It is approximately equivalent to the degree of saturation of each phase
THERMODYNAMIC ACTIVITY
It is a bond in which a hydrogen atom serves to hold two other atoms together.
HYDROGEN BOND
The H-bond is usually formed only between:
HYDROGEN AND ELECTRONEGATIVE ATOMS
Most common atoms capable of forming H-bonds
FLUORINE
OXYGEN
NITROGEN
Atoms capable of forming H-bonds to a lesser extent:
CHLORINE
SULFUR
The compounds that are capable of forming hydrogen bonding are only:
SOLUBLE IN WATER
The hydrogen bonds occur within one molecule
INTRAMOLECULAR HYDROGEN BONDING
The hydrogen bonds occur between two or more molecules
INTERMOLECULAR HYDROGEN BONDING
They are frequently much weaker than the other.
INTERMOLECULAR; INTRAMOLECULAR
It would greatly increase its potential for aqueous solubility.
MULTIPLE HYDROGEN BONDING GROUPS IN ANY DRUG MOLECULE
It is essential for all the drug molecules to transport to the site of action on a receptor.
MINIMAL AQUEOUS SOLUBILITY
H-bond strength of acetic acid dimer in vapour state
7.64 kcal/mol
H-bond strength of acetic acid dimer in benzene
4.85 kcal/mol
In water, the h-bond strength is:
4.5 kcal/mol
In ice, the bond strength is:
6 kcal/mol
The physical states of substances, such as water, DNA, protein and various drug molecules are maintained by:
HYDROGEN BONDING
The most frequently observed H-bonds in biological systems are between the:
HYDROXYL (OH)
AMINO (NH)
No analgesic property
Melting point: 127 degrees C
Insoluble in Water
Slightly soluble in Ether
Forms intermolecular H-bond
1-Phenyl-3-methy-5-pyrazolone
Good analgesic agent
Melting point: 112 degrees C
Soluble in Water
Moderately soluble in Ether
Does not form intermolecular h-bond
1-Phenyl-2,3-dimethy-5-pyrazolone (antipyrine)
Increase in ionization INTENSIFIES A DRUG’s WATER SOLUBILITY and DECREASES ITS LIPOSOLUBILITY
Drugs cross cellular membranes in UNDISSOCIATED forms as:
INTACT MOLECULES
Drugs cross cellular membranes in DISSOCIATED form as:
IONS
Are predominantly of the UNIONIZED form at the LOWER pH of the gastric fluid, and absorbed from the stomach as well as intestine.
WEAKLY ACIDIC DRUGS
Some very weak acidic drugs whose pKa are greater than 7 and are unionized at all pH values
PHENYTOIN
MANY BARBITURATES
They are poorly absorbed in the stomach since they are present largely in the ionized form at low pH
MOST WEAK BASES
Those with pKa values between 5 and 11, shows pH dependent absorption.
STRONG BASE
This stronger base has a pKa > 11 and are ionized throughout the gastrointestinal tract and tend to be POORLY ABSORBED.
GUANITHIDINE
The liposolubility is affected by pH of the environment medium and by the degree of dissociation pKa.