(1) Ionization
(2) Partition coefficient
(3) Solubility
(4) Protein binding
(5) Chelation
(6) Bioisosterism
(7) H-bonding
(8) Optical and geometrical isomerism
(1) Ionization -
• When any drug molecule accept release the electron from its outermost cell then it convert into ions and this process is called ionization.
• If that molecule release the electron then they form cation and if the molecule accept the electrons then they called anion.
The ionization process is very important in the study of pharmacokinetics of any drug.
(2) Partition coefficient -
• Partition coefficient decides the hydrophilic and lipophilic nature of any drug.
• It can be defined as the ratio of drug dissolved into octanol upon drug dissolved into water. It is denoted by log P.
Log P = x of drug in octanol / x of drug in water
• If the value of partition coefficient is less than one, the nature of drug is hydrophilic.
If the value of partition coefficient is more than one, the nature of drug is lipophilic.
• The partition coefficient of a medicine depends upon following factor -
(i) pH
(ii) Cosolvent
(iii) Surfactant
(iv) Complexation
(3) Solubility -
Solubility is the dissolution of solid particle inside the solvent and form a saturation solution.
Types of solubility -
(1) On the basis of solvent :
(a) Aqueous solubility - When solid particle dissolved into water.
(b) Non aqueous solubility - When solid particle dissolved into solvent other than water.
(2) On the basis of kinetics -
(a) Equilibrium solubility -
When excess amount of solute is dissolved into the particular solvent then after dissolution there is equilibrium condition between undissolved solute to its saturated solution then this type of solubility is called equilibrium solution.
(b) Kinetic solubility -
When the weak acid or weak basic drug is dissolved into non aqueous solvent such as strong base, strong acid then due to levelling effect solubility is increased and this type of solubility is called Kinetic solubility.
Factors affecting solubility -
(i) Temperature - Temperature is directly proportional to solubility.
(ii) Pressure - On increasing pressure, solubility increase because the distance between solute and solvent particle decrease.
(iii) Polymorphism - Amorphous is directly proportional to solubility and crystalline is inversely proportional to solubility.
(iv) Polarity - It depends on principle like disolve like.
(4) Protein binding -
We have already discussed protein binding.
(6) Bioisosterism -
• Those chemical molecule which have same electronic configuration they have different physical and chemical properties they are called bioisosteres of each other and the process of study of bioisosteres is called bioisosterism.
• The term bioisosterism is derived from two word bio and isosterism.
• Bio means drug in biological system and isosterism means they have similar structure and properties.
Types of bioisosteres -
(i) Classical
(ii) Non classical
(7) H-bonding -
When any highly electro negative F, O or N is attached with hydrogen atom then hydrogen becomes electron deficient and they make a weak attraction force with another electron rich molecule and this is called H-bonding this is denoted by dotted line.
MCQ CORNER
V1a receptors are located on
(A) Vascular smooth muscle
(B) Uterine
(C) Adipose tissue
(D) All of the above
Ans : (D) All of the above
V1b receptors are present on all of the following EXCEPT
(A) Anterior Pituitary
(B) Posterior Pituitary
(C) Certain area in Brain
(D) Certain area in pancreas
Ans : (B) Posterior Pituitary
Desmopressin is drug of choice in
(A) Diabetes mellitus Type 01
(B) Diabetes Insipidus
(C) Diabetes mellitus Type 2
(D) Both A and C
Ans : (B) Diabetes Insipidus
Desmopressin is
(A) Selective V1 agonist
(B) Selective V1 Antagonist
(C) Selective V2 Agonist
(D) Selective V2 Antagonist
Ans : (C) Selective V2 Agonist
Amiloride is drug of choice for
(A) Lithium induced nephrogenic DI
(B) Indomethacin induced nephrogenic DI
(C) Antibiotic induced nephrogenic DI
(D) None of the above
Ans : (C) Antibiotic induced nephrogenic DI
The V1 receptors function mainly through
(A) Phospholipase C-IP3/DAG pathway
(B) Sodium channel
(C) Na and Ca symporter
(D) None of the above
Ans : (A) Phospholipase C-IP3/DAG pathway
Glomerular filtration rate is dependent on
(A) Pumping action of heart
(B) Magnitude of renal blood flow
(C) Relative dimension of afferent and efferent glomerulus vessels
(D) All of the above
Ans : (D) All of the above
Renin release is due to
(A) Sympathetic stimulation of kidney
(B) Parasympathetic stimulation of kidney
(C) Hypotension
(D) Diuresis
Ans : (A) Sympathetic stimulation of kidney
Force diuresis with saline and furosemide is no longer used recommended to treat poisonings
(A) True
(B) False
Ans : (A) True
There are no injectable preparation of thiazide drugs
(A) True
(B) False
Ans : (A) True
Indomethacin and other NSAID diminish the action of high ceiling diuretic by
(A) PG synthesis in kidney
(B) Increase Renin release
(C) Inhibition of PG synthesis
(D) Inhibition of renin release
Ans : (A) PG synthesis in kidney
Aldosteron antagonist may work as
(A) Potassium sparing diuretics
(B) Antidiuretics
(C) Thiazide like diuretics
(D) Both A and C
Ans : (A) Potassium sparing diuretics