It contains pharmacokinetic parameters, factors affecting on it, routes of drug excretion, factors affecting on dose of drug.

1. General Pharmacology
Prepared by
Ms. Nisha S. Mhaske
M.Pharm (Q.A.T)
Lecturer, PRES’s COPD, Chincholi.
Email : nisha.mhaske@pravara.in

2. Agonist
 A drug which combines with receptor and gives a
pharmacological response is called agonist.

3. Antagonist
 A drug which combines with receptor but does not
produce pharmacological response and only
blocks the receptor is called as antagonist.

4. Affinity
 The ability of a drug to get bound to the
receptor is called affinity of a drug for the
receptor.
Efficacy or Intrinsic activity
 The ability of a drug to give a pharmacological
action after combination with receptor is called
as efficacy of a drug.

5. Receptor
 “A receptor is a specific functional cellular
component which when combines with drug
molecules produces pharmacological action.”
 Receptors are:
 Protein or lipoprotein in nature
 Situated on the cell membrane or within the cell
(Cytoplasm, nucleus)
Location of receptors
 On the cell membrane- Insulin
 Within cytoplasm-steroid receptor
 Within nucleus- thyroid receptor

6. Common receptors & their subtypes
Cholinergic receptor or Cholinoreceptor
 Muscarinic
 Nicotinic
Adrenergic receptor or Adrenoreceptor
 Alpha
 Beta
Histamine receptor
 H1
 H2
 H3
 H4

7.  Dopamine receptor
 D1
 D2
 5-Hydroxy tryptamine receptor
 5-HT1
 5-HT2
 5-HT3
 Opoid receptor
 Mu
 Kappa
 Delta
 GABA Receptor
 Prostaglandin receptor

9. Pharmacokinetic Parameters
 Absorption- is the entry of drug molecules into
the blood via the mucous membrane of the
alimentary or respiratory tract or from the site of
injection.
 Distribution- is the movement of the drug
molecules between the water, lipid & protein
constituents of the body.
 Metabolism or Biotransformation- is the
process of alteration in the structure of the drug
molecule in the body, specially in the liver.
 Excretion or Elimination- is the removal of the
original drug molecule or its metabolites from the
body.

10. Pharmacokinetic
What the body does to
the Drug
Absorption
- Drug
taken into
the body
Distribution-
Drug moved
into tissues
Metabolism-
Drug changed
so can be
excreted
Excretion-
Drug
removed
from the
body.

11. What is membrane???
 It consist of bi-molecular layer of lipid molecule, coated with
a protein layer on each surface.
 Also has small pores & active transport system.
 The ability of the drug to cross this membrane depends on
its chemical & physical properties.

15. Absorption of Drugs
 Absorption- the passage of drug from route of
administration into blood circulation is known as
absorption.
 Types/process/mechanism/ways of absorption
 The absorption of drug across the cell membrane
occurs by following ways:-
 The cell membrane contains small pores & only
water soluble molecules can pass through them.
A. Passive Transfer B. Specialized transport
a.
Simple
Diffusion
b.
Filtration
a. Active
Transport
b.
Facilitated
diffusion
c.
Pinocytosis

16. A. Passive Transfer
 Means that a drug or substance is taken up across
a membrane without the need of energy.
a. Simple Diffusion
 Requires no energy for transfer.
 Depends on the difference in the concentration of
drug on either side of the membrane.
 Fat and water soluble molecules of small size may
cross the membrane by simple diffusion.
 Eg- alcohol, urea, water itself diffuses passively
through aqueous pores of the membrane.

17. b. Filtration
 Small, soluble & polar drugs are absorbed by
porous membrane.
 Larger molecule size- block the pores.
 Eg- glomerular filtration of kidney

18. B. Specialized transport
a. Active transport process
 Requires energy & is dependent on physical property
of the membrane.
 In this process, the carrier molecule combines with
drug molecule and forms a drug carrier complex on
one side of the membrane.
 This complex then diffuses through the membrane and
dissociates into carrier and drug molecule when
reaches other side of the membrane.
 After that carrier molecule returns to the original
surface to repeat the process.
 This transport system is rapid than simple diffusion.
 Eg- ions such as, Na + , K +, I−, amino acids, some
drugs, strong acids, strong bases and weak
electrolytes in ionized form, glucose, pyrimidines &
some antimetabolites are transported by this process.

20. b. Facilitated diffusion
Like passive transfer this process is also not
energy dependent.
The movement of drug is from high
concentration to low concentration.
There is no involvement of carrier system in this
system.
Process is rapid than passive transport process.

21. c. Pinocytosis
 In this process, cell forms a cavity like pseudopodium
and particles are taken inside the cell.
 In this process, the cell takes up the fluid or
micromlecule from its surrounding
 This process is important for unicellular organism like
amoeba.

22. Factors affecting on absorption of
drug
Physical state of drug Functional integrity of GIT
Particle size PH of drug
Concentration of drug Formulation
Area of absorbing surface Presence of other agent
Physical & mental state of the patient Presence of food in GIT
O
r
A. Physical
Properties
B. Dosage
form
C. Physiological Factors
a. Physical state a. Particle size a. pH
b. Lipid & water
solubility
b. Formulation b. Ionization
c. Presence of other agents
d. Presence of disease
e. Area of absorption

23. A. Physical Properties
a. Physical state
 Liquids are better absorbed than solids.
 Crystalloids are better absorbed than colloids.
 Amorphous form is better absorbed than
crystalline.
b. Lipid & water solubility
 Higher the lipid solubility greater is the rate of
absorption from GIT.
 Eg- fat soluble vitamin A,D,E & K are better
absorbed.

24. B. Dosage Form
a. Particle size
 Smaller particle size provides greater surface
area for absorption.
 Large aggregates of an active compound do
not disintegrate rapidly even though kept
prolong time in contact with gastric juices.
 Hence smaller the particle size greater is the
rate of absorption.
 Eg- chloramphenicol, steroids etc.

25. b. Formulation
Substances like lactose, sucrose, starch,
calcium phosphate, calcium lactate are used
as inert diluents in formulating tablets,
powders.
These agents may interfere with active drug &
its absorption.
Eg- calcium & Magnesium ions reduce the
absorption of tetracycline because tetracycline
forms complex with Ca2+ and Mg2+, hence
such formulation should not be made.

26. C. Physiological Factors
a. pH
 Acidic drugs are rapidly absorbed in stomach
 Eg- salicyales, barbiturates
 Basic drugs are rapidly absorbed in intestine due
to respective pH ranges.
b. Ionization
Unionized drugs are lipid soluble while ionized
are water soluble agents. Hence unionized
drugs are better absorbed than ionized drugs.

27. c. Presence of other agents
Vitamin C increases the absorption of drug
from GIT
The absorption of fat soluble vitamins
increases in presence of liquid paraffin.
d. Presence of disease
In presence of disease absorption of drug is
reduced.
In presence if liver cirrhosis, achlorhydria, rate
of absorption in low.
In diarrhoea, dysentery increased intestinal
motility that reduces absorption.

28. e. Area of absorption
Drugs are better absorbed in intestine than in
stomach because of larger surface area of
intestine.
f. Gastro-Intestinal transit time
Absorption of drug is influenced by presence of
food, volume, viscosity, tone of gastric content.
Rapid absorption occurs if drugs are
administered before meal.
(Note-If unionized drugs/water insoluble drugs taken
in empty stomach, it sticks to gastric mucosa and
produce irritation, peptic ulceration, GIT bleeding.
Hence to avoid such effects drugs should be taken
after meal.)

30. Distribution of Drugs
 Distribution of drugs involves transport of drugs to the
tissues.
 The body fluids acts as solvent and vehicles.
 Drugs may be distributed in the body as follows:-
 Extracellular fluid (26%)
 In blood
 Adipose tissue (Fat)
 Other body tissues (Organs)
 Transcellualr fluid compartments
o Eg- fluids in GIT,
o Fluids in bronchi
o Fluids in CSF (Cerebrospinal fluid)

31.  In blood, the majority of drugs are simply
dissolved in serum water but some of them
are bound to blood proteins such as albumin,
globulin etc.
 Distribution of drugs into the brain & CSF
depends upon the lipid soluble properties of
drug.
 Lipid soluble drugs enter in the brain more
easily.
 Similarly, lipid soluble compound cross the
placental barrier and show similar
pharmacological effects in both mother &
fetus.

32. Factors affecting on Distribution of
drug
 pH
 Plasma Protein binding
 Physicochemical properties of drug-
distribution of drugs depend upon lipid solubility
of drug
 Enterohepatic circulation
 Route of administration
 The presence of active transport system
 Specific barriers

33. Plasma Protein binding-
PPB
After absorption, the drug circulates in the
blood and binds with plasma proteins which
is known as protein binding of drug.
Due to protein binding of drug, it is not available
for diffusion into extracellular compartments.
Thus there is no excretion of drugs and prolongs
the duration of action of drug.

34. Importance of protein binding of
drugs
Protein binding makes the drug inactive.
The drug becomes impermeable to membrane
after protein binding. This reduces metabolism
and excretion of drugs.
Protein binding acts as a storage site of a
drugs.
Protein binding also reduces the amount of drug
available for filtration at the glomeruli and hence
reduces it’s excretion.

35. Enterohepatic circulation
Some drugs are extracted from the body by liver
and then excreted into the small intestine via bile
further they are reabsorbed across the mucosa
back into the blood.

37.  “The alteration of drug within a living organism
so as to modify its activity or its nature is known
as biotransformation or metabolism.”
 The enzyme involved in the biotransformation of
drugs are called “Microsomal enzymes”.
 Some drugs are biotransformed into more active
compounds.
 Eg- Levodopa (Inactive) Dopamine (Active)
in brain.
• Dopamine is neurotransmitter- control brain activity
 Diazepam Oxazepam (Active)
• Belongs to benzodiazepines- act on CNS &
produces calming effect.
 Phenylbutazone Oxyphenbutazone
(Active NSAIDs)

39. Pathways
of
Metabolis
m
Oxidatio
n
Reduction
Hydrolysis
Conjugation

40. Oxidation
 Microsomal oxidation may involve the introduction of a
hydroxyl group in to the drug molecule.
 Eg- conversion of salicylic acid into gentisic acid
 Gentisic acid is an active metabolite of salicylic
acid degradation.
o Gentisic acid- is a dihydroxybenzoic acid
o It is derivative of benzoic acid and minor product of the
metabolic break down of aspirin, excreted by the
kidneys.
o It is also found in the African tree Alchornea cordifolia
and in wine. Formula- C7H6O4—154.12 g/mol.

41. Reduction
Many halogenated compounds and nitrated
aromatic compounds are reduced by the
microsomal enzymes.
Eg-halothane, chloramphenicol (Antibiotic)
Hydrolysis
It is usually carried out by enzymes esterase's that
hydrolyze the esters.
Eg- Procaine, Ach (Acetylcholine) are hydrolyzed
by esterase.

42. Conjugation
 This is a synthetic process by which a drug or its
metabolite is combined with an endogenous
substances resulting in various conjugates such as
glucoronides, ethereal sulphates and amino acid
conjugates.
 Eg- phenobarbitone is oxidized to its hydroxy
derivative which is conjugated with glucoronic acid.

44. “Removal of drug or its metabolite
from the body is called as excretion or
elimination”.
The important channels of excretion of drugs are as
follows
1. Kidney
2. Lungs
3. Skin
4. Bile
5. Intestine
6. Milk

45. 1. Kidney
 the kidney acts as a primary organ for the excretion of
most of the drugs.
 The rate of glomerular filtrate, tubular reabsorption
and tubular secretion influences the rate of excretion
of drugs.
 Eg- weak acids are quickly eliminated in an alkaline
urine.
 Weak bases are rapidly excreted in an acidic urine.
2. Lungs
 Volatile general anesthetics eg-diethyl ether,
chloroform, halothane and certain other drugs like
paraldehyde and alcohol are partially excreted by the

46. 3. Intestine
 Some substances which are not fully absorbed
from GIT are excreted in the feces.
 Eg-purgatives like Senna.
(Purgatives- evacuation, emptying, cleansing of
bowels)
4. Skin
 Some metals like arsenic and mercury may be
partly excreted through the skin.
 Arsenic gets deposited in the hair follicles on
prolonged administration.
 The phenomenon is useful for detecting arsenic
poisoning.

47. 5. Bile
 The drugs such as erythromycin are excreted in
the urine in small amounts but appear in high
concentration in bile & are partially excreted into
the intestine through the bile.
6. Milk
 Antibiotics are deposited in the milk.
 Drugs like chloramphenicol, chlorpromazine,
diazepam are deposited into milk and excreted via
milk.
7. Saliva
 Certain drugs like iodides and metallic salts are
excreted in the saliva.
 Eg- lead compounds deposited as lead sulphide
produce blue line on gums.