Introduction of Pharmacology

1. INTRODUCTION OF
PHARMACOLOGY

2. PHARMACOLOGY
( Greek : Pharmacon – drug; logos – a study or
discourse in)
Pharmacology is the science of drugs. In a
broad sense, it deals with interaction of
exogenously administered chemical molecules (
drugs) with living systems.
It encompasses all aspects of
knowledge about drugs, but most importantly
those that are relevant to effective and safe use
for medicinal purposes.

3. THE TWO MAIN DIVISIONS OF
PHARMACOLOGY
PHARMACODYNAMICS PHARMACOKINETICS

4. PHARMACODYNAMICS
( Greek : dynamis – power)
What the drug does to the body is called
Pharmacodynamics.
This includes
- Physiological and biochemical effects of drugs and
- their mechanism of action at cellular and organ system
levels.

5. PHARMACOKINETICS
(Greek : Kinesis – movement )
What the body does to the drug is called
Pharmacokinetics. This refers to movement
of the drug and its alteration within the
body, including
Route of administration,
Absorption,
Distribution,
Biotransformation and Excretion

6. RELATIONSHIP BETWEEN BODY AND DRUG
BODYDRUG
What the BODY does to the DRUG (pharmacokinetics)
What the DRUG does to the BODY (pharmacodynamics)

7. DRUG ( French: Drogue – a dry herb)
“It is the single active chemical entity present in a medicine
that is used for diagnosis, prevention, treatment or cure of a disease”.
This disease oriented definition of drug does not include
contraceptives.
WHO (1966) has given a more comprehensive definition :–
“Drug is any substance or product
that is used or is intended to be used
to modify or explore
physiological systems or pathological states
for the benefit of the recipient ”.

8. The benefits of the recipient (human or an
animal) include:-
1. Diagnosis
2. Prevention
3. Control (suppression)
4. Cure of the disease.

9. DIAGNOSIS
means the determination of the nature of a case of a disease
or the distinguishing of one disease from another.
It is based on signs, symptoms and laboratory findings
e.g. Barium sulfate ( a radio-opaque substance) is
usually used to fill the GIT so that the defects can be
exposed for X-ray.
Here barium sulfate is the drug used for the diagnosis
of the disease.

10. PREVENTION ( prophylaxis)
In primary prevention the person does not
have the disease and is to be prevented from getting
it, for e.g. vaccinations to prevent occurrence of
infection in the body, e.g. Poliovaccine is used for
the prophylaxis of poliomyelitis.
In secondary prevention the patient has the
disease and the objective is to reduce risk factors and
to retard progression of disease. (e.g. lipid-lowering
drugs in atherosclerosis ).

11. CONTROL (SUPPRESSION)
When a drug is used
continuously or intermittently
to maintain health without attaining cure
as in hypertension, diabetes mellitus, asthma
Or to control symptoms, such as pain & cough,
while awaiting recovery from the causative disease,
it is called control or suppression of disease or symptoms,
for e.g. use of analgesic to suppress pain while awaiting healing of
fracture.

12. CURE OF THE DISEASE
It implies the therapy that eliminates
the disease completely and then the drug is
withdrawn afterwards, for e.g. in bacterial and
parasites infections.
Metronidazole is commonly used for the
treatment of amebiasis with the purpose to cure
the disease.
However a single drug may not fulfill all the
purposes like diagnosis, prevention, control or
cure of a disease.

13. Drugs
Drugs can be defined as chemical agents that
uniquely interact with specific target molecules in
the body, thereby producing a biological effect.
Drugs can be
stimulatory or
inhibitory

14. Drugs
• Drugs, as well as hormones, neurotransmitter,
autacoids and toxins can make possible the
transfer of information to cells by interaction
with specific receptive molecules called
“receptors”.
Receptor
DRUG

15. Drugs
• Drugs interact with biological systems in ways that
mimic, resemble or otherwise affect the natural
chemicals of the body.
• Drugs can produce effects by virtue of their acidic or
basic properties (e.g. antacids, protamine), surfactant
properties (amphotericin), ability to denature proteins
(astringents), osmotic properties (laxatives, diuretics),
or physicochemical interactions with membrane lipids
(general and local anesthetics).

16. PHARMACO-THERAPEUTICS
It is the application of pharmacological information together with knowledge of the
disease for its prevention, mitigation or cure.
For e.g. if we take aspirin in fever, it lowers the temperature.
When atenolol is used it reduces the blood pressure.
When glibenclamide is taken it reduces the blood sugar level.
That is, lowering body temperature, reducing blood pressure or blood sugar levels
are all considered as drug effects or therapeutic actions of drugs.
SITE OF DRUG ACTION
Now the question is where and how the effect is produced. For e.g atenolol on the
heart to reduce cardiac output and peripheral resistance i.e. to reduce high blood
pressure,
glibenclamide on the beta cells of the islets of Langerhans of the pancreas to release
insulin.
Here, heart, blood vessels and beta cells of islets of Langerhans of pancreas are the
sites of drug action.

17. PHARMACOLOGICAL EFFECTS
Pharmacological effects may be defined as the physiological
and/or biochemical changes in the body produced by a drug in therapeutic
concentrations. No drug has single pharmacologic effect rather it usually
produces several pharmacological effects.
The pharmacologic effects of a drug may be classified as
desired and undesired effects even when used in usual dose. Undesired effects
are further classified as beneficial, harmful and harmless effects.
PHARMACOLOGICAL EFFECTS
DESIRED EFFECTS UNDESIRED EFFECTS
BENIFICIAL HARMFUL HARMLESS

18. PLASMA CONCENTRATION OF DRUG
The effectiveness, ineffectiveness or toxicity of a drug depends on
its concentration in plasma.
For example, therapeutic effect is unlikely if the plasma
concentration of digoxin is less than 1nmol/L. Beneficial effect with
a low risk of toxicity is obtained when its concentration ranges
between 1 to 3.8nmol/L. But the risk of its toxicity is increased
considerably when its plasma concentration increases above
3.8nmol/L.
A barbiturate can be taken as another example, which in
lower doses produces sedation but when its concentration is
increased it can develop hypnosis. Even coma and death may occur
with further increase in concentration.

19. CLINICAL PHARMACOLOGY
It is the scientific study of drugs in man. It includes,
Pharmacodynamic and pharmacokinetic investigation in healthy
volunteers and in patients;
Evaluation of efficacy and safety of drugs and comparative trials
with other forms of treatment;
Surveillance of drug use, adverse effects, etc.
The aim of clinical pharmacology is to generate data for optimum use of
drugs.
CHEMOTHERAPY
It is the treatment of systemic infection or malignancy with
specific drugs that have selective toxicity for the infecting organism or
malignant cells with no or minimal effects on the host cells.

20. PHARMACY
It is the art and science of compounding and
dispensing drugs or preparing suitable dosage forms for
administration of dugs in man or animals.
It includes collection, purification, isolation,
synthesis, standardization and quality control of medicinal
substances.
The large scale manufacture of drugs is called
Pharmaceutics. It is primarily a technological science.

21. TOXICOLOGY
It is study of poisonous effects of drugs and other
chemicals (house–hold and environmental pollutants,
industrial and agricultural chemicals) with emphasis on
detection, prevention and treatment of poisoning.
It also includes the study of adverse effects of drugs,
since same substance can be a drug or a poison, depending
on its dose.

22. ESSENTIAL DRUG CONCEPT
The WHO has defined Essential Drugs as ‘ those that satisfy the healthcare needs of
majority of the population; they should therefore be available at all times in
adequate amounts and in appropriate dosage forms’.
It has been realized that only a handful of drugs out of the multitude available can meet
the health care needs of majority of the people in any country, and that many well
tested and cheaper drugs are equally ( or more) efficacious and safe as their newer
more expensive congeners. For optimum utilization of resources, government
should concentrate on these drugs by identifying them as Essential Drugs.
The WHO has laid down criteria to guide selection of an essential drug. Some of
its important points are as follows:
i. Adequate data on drug’s efficacy and safety should be available from clinical
studies. It should be available in a form.
ii. In case of two or more similar drugs, choice should be made on the basis of their
relative efficacy, safety, quality, price and availability . Cost benefit ratio should
be a major consideration.
iii. Selection of essential drugs should be a continuous process which should take into
account the changing priorities for public health planning, epidemiological
conditions, availability of better drugs & progress in pharmacological knowledge.

23. PHARMACOLOGY TODAY
As with other biomedical disciplines, the boundaries
of pharmacology are not sharply defined nor are they constant.
Its exponents are, as befits pragmatists, ever ready to poach on
the territory and techniques of other disciplines.
If it ever had a conceptual and technical core that it
could really call its own, this has now dwindled almost to the
point of extinction, and the subject is defined by its purpose, to
understand what drugs do to living organisms and more
particularly how their effects can be applied to therapeutics.
Figure in next slide shows the structure of pharmacology as it
appears today.

25. BIOTECHNOLOGY
Originally , this was the production of drugs or other useful products
by biological means e.g. antibiotic production from microorganisms.
Currently in the biomedical sphere, biotechnology refers mainly to the
use of recombinant DNA technology for a wide variety of purposes, including
the manufacture of therapeutic proteins, diagnostics , genotyping, etc.
There are also many non-medical applications including agricultural,
forensic , environmental sciences and etc.
PHARMACOGENETICS
This is the study of genetic influences on responses to drugs.
Originally , pharmacogenetics focused on familial idiosyncratic drug reactions,
where affected individuals show an abnormal, usually adverse, response to a
class of drug.

26. PHARMACOGENOMICS
This recent term overlaps with pharmacogenetics,
describing the use of genetic information to guide the choice of
drug therapy on an individual basis. The underlying assumption
is that differences between individuals in their response to
therapeutic drugs can be predicted from their genetic makeup.
On this principal, discovering which specific gene
variations are associated with a good or poor therapeutic
response to a particular drug should enable individual tailoring
of therapeutic choices on the basis of an individual’s genotype.
So far, the concept is largely theoretical, but if it
proves valid, the consequences for therapeutics will be far
reaching.

27. PHARMACOEPIDEMIOLOGY
This is the study of drug effects at the population
level. It is concerned with the variability of drug effects between
individuals in a population, and between populations.
It is an increasingly important topic in the eyes of
the regulatory authorities who decide whether or not new drugs
can be licensed for therapeutic use.
Pharmacoepidemiological studies also take into
account patient compliance and other factors that apply when the
drug is used under real – life conditions.

28. PHARMACOECONOMICS
This branch of health economics aims to quantify in
economics terms the cost and benefit of drugs used
therapeutically.
It arose from the concern of many governments to
provide for healthcare from tax revenues, raising questions of
what therapeutic procedures represent the best value for money.
This, of course raises fierce controversy, since it ultimately
comes down to putting monetary value on health and longevity.
As with Pharmacoepidemiology, regulatory authorities are
increasingly requiring economic analysis, as well as evidence of
individual benefit, when making decisions on licensing.

29. CONSIDERATIONS BEFORE TREATING PATIENTS
Before treating any patient with drugs, doctors should have made up their
minds on 8 points :
i. Whether they should interfere with the patient at all and if so;
ii. What alteration in the patient’s condition they hope to achieve
iii. That the drug they intend to use is best capable of bringing this about.
iv. How they will know when it has been brought about
v. That they can administer the drug in such a way that the right concentration
will be attained in the right place at the right time and for the right
duration.
vi. What other effects the drug may have and whether these may be harmful
vii. How they will decide to stop the drug.
viii. Whether the likelihood of benefit, and its importance, outweighs the
likelihood of damage, and its importance, i.e. to consider benefit verses
risk, or efficacy in relation to safety.

30. FACTORS INFLUENCING DRUG
RESPONSES
When a patient is given a drug the responses are the resultant of
numerous factors :
- The pharmacodynamic effect of the drug and interactions with
any other drugs the patient may be taking.
- The pharmacokinetics of the drug and its modification in the
individual due to genetic influences or disease.
- The act of medication , including the route of administration.
- What the doctor has told to patient.
- The patient’s past experience of doctors.
- The social environment , e.g. whether supportive or dispiriting
The relative importance of these factors varies according to
circumstances.

31. DRUG HISTORY
The reasons for taking a drug history from patients are :
- Drugs can be cause of disease. Withdrawal of drugs can also cause
disease,
- Drugs can conceal disease,
- Drugs can give diagnostic clues, e.g. ampicillin and Amoxycillin
causing urticaria in infectious mononucleosis – a diagnostic adverse
effect.
- Drugs can cause false results in clinical chemistry test.
- Drugs history can assist choice of drugs in the future.

32. WARNINGS AND CONSENT
Doctors have a professional duty to inform and to warn,
so that patients, who are increasingly informed and educated, may make
meaningful personal choices which it is their right to do ( unless they opt
to leave the choice to the doctor, which is also their right to do ).
KINDS OF WARNINGS TO PATIENTS
- Warnings that will affect the patient’s choice to accept or reject the
treatment.
&
- Warnings that will affect the safety of the treatment once it has begun,
e.g. risk of stopping treatment, occurrence of drug toxicity.

33. PATIENT’S COMPLIANCE
Patient compliance is the extent to which the actual behaviour of the
patient coincides with medical advice and instructions : it may be
complete, partial, erratic, nil or there may be over-compliance.
PRIME FACTORS FOR POOR PATIENT’S COMPLIANCE
- Patient dissatisfaction with the doctor, poor patient – doctor
relationship
- Lack of motivation
- Forgetfulness ( Unintentional noncompliance)
- Deliberate intention
- Lack of information
- Frequency and complexity of drug regimen

34. DOCTOR’S COMPLIANCE
Doctor compliance is the extent to which the behaviour of
doctor fulfills their professional duty :
- Not to be ignorant.
- To adopt new advances when they are sufficiently proved.
- To prescribe accurately.
- To refrain from inappropriate prescription.
-To tell patients what they need to know.

35. SELF MEDICATION
Self medication is appropriate for :
- Short term relief of symptoms where accurate diagnosis is
unnecessary.
- Uncomplicated cases of some chronic and recurrent
diseases ( where a medical diagnosis & prescription would
have already been made)