Dr. Haji Bahadar discusses pharmacodynamics, which is the biochemical interaction of drugs with the body that produces pharmacological effects. There are two main types of interactions: receptor-mediated and non-receptor mediated. Receptor-mediated interactions involve drugs binding to receptors on cells to initiate a response, while non-receptor mediated interactions occur through processes like osmosis, adsorption, chemical reactions, and enzyme inhibition. The document provides detailed explanations and examples of both types of pharmacodynamic interactions.

1. Dr. Haji Bahadar, PharmD, PhD
Assistant Professor, KMU-IPMS
Email: bahadarph@gmail.com

2.  In pharmacology, the term pharmacodynamics
means a specific biochemical interaction of
drug substance with target organ producing
pharmacological effect
 Pharmacodynamics is the mechanism where
drugs exert their effects on the body. To
produce therapeutic or toxic effects drugs
interact in a different ways in the body

3. 1. Non receptor mediated
2. Receptor mediated
1. Non receptor mediated
a) By Physical action:
 osmosis: some drugs exert their
effect by osmotic pressure. 20%
mannitol.
 Adsorption: Adsorption is the
adhesion of molecules of gas,
liquid, or dissolved solids to a
surface. Charcoal adsorbs toxins
 Demulcent: coating the
membrane. Example. Sucralfate

4. b. By chemical reaction: antacids and weak
bases: they neutralize the gastric acids
c. Chelation: Chelation means "to grab" or "to
bind. Chelation therapy is a medical
procedure that involves the administration
of chelating agents to remove heavy metals
from the body. Chelating agents are chemical
compounds that react with metal ions to form
a stable, water-soluble complex.
Deferoxamine for iron. Dimercaprol for
arsenic

5.  C. By enzymes: Some drugs exert effect by
acting on enzymes. For example; ramipril
inhibit the angiotensin converting enzyme,
Allupurinol inhibit xanthine oxidase enzyme
to prevent uric acid formation
D.Through ion channels: local anesthetics
E. Through antibody production

6.  Receptor: It is a macromolecule or binding site
located on cell surface or inside the effector cell
which recognize drug and initiate the response.
 Affinity: Ability of a drug to combine with the
receptor. D + R D-R complex = Effect
 Efficacy: Capacity of a drug receptor complex (D-R) to
produce an action.
 Agonist: it is a drug that combines with receptor and
elicit a response (has affinity and efficacy).
 Antagonist: it is a drug that combines with a receptor
without producing responses. It blocks the action of
the agonist (has affinity but no or zero efficacy).
 Partial Agonist???????? self

7. 1. G-protein coupled receptors (GPCR)
2. Receptors with intrinsic ion channel
3. Enzyme linked receptors
4. Transcription factors (receptors for gene expression)

8.  Downregulation: An decrease in the number of
receptors on the surface of target cells. Effect: the
cells becom less sensitive to a hormone or another
agent. For example, insulin receptors may be
downregulated in type 2 diabetes. Similarly, chronic
use of salbutamol down regulate beta receptors in
lungs leading to decrease effect
 Reason: regular and prolonged use of an agonist.
 Upregulation: An increase in the number
of receptors on the surface of target cells, making the
cells more sensitive to a hormone or another agent.
 Reason: some time natural. rise in receptors for
oxytocin in third trimester of pregnancy
 Other reasons: prolonged use of an antagonist
(propranolol)

9. Dose response curve describes the relationship
between effect and drug.
Phases of a Dose Response Curve
There are three phases of a dose response curve.
First, the curve is flat as the amount of drug
given is not great enough to initiate a response.
In the second phase, the curve steadily rises, with
each increase in the drug dose there is also an
increased in desired response. Finally, the curve
plateaus at the top, indicating that any further
increases in drug dose will not increase a drug
response

10. Drugs are commonly divided into two basic categories: agonists and
antagonists. Agonists are drugs
that bind and activate receptors.Antagonists are drugs that bind to
receptors without activating them

11.  Quantal dose response - is the relationship
between three : No. of patients, response and
dose. For certain other drugs, the responses are
not observed on a continuous basis. Such drugs
may either show their effect or not at all – for
example, prevention of seizures by phenytoin.
Such responses are called quantal or all-or-
none.
Graded response - is relationship between two :
dose and drug effect. That means how much
amount of drug is required to decrease 20%
blood pressure in an individual.

13.  Drugs have therapeutic effects, toxic effects,
and in some cases lethal effects. Side effects
and lethal effects are typically dose-
dependent, and can be measured by defining
the dose that produces a toxic effect in 50%
of the population (TD50) and (at least in
animals) lethal effects in 50% of the
population (LD50).
 Therapeutic Index (TI), which is defined as
the ratio between the TD50 and ED50
or TI=TD50/ED50.

15.  Additive effect: When two drugs with similar
mechanisms are given together, they produce
effect equal to the sum of individual effects.
2+2=4
 Synergism or synergistic effect: when the effect of
two drugs exceeds the sum of their individual
effects, this is referred to
as potentiation or synergism.

16.  Drug absorption, distribution, excretion,
metabolism, bioavailability, factors etc.