Pharmacology is the study of drug action on living organisms. Pharmacokinetics describes the processes of absorption, distribution, metabolism, and excretion of drugs in the body. Pharmacodynamics examines how drugs act on the body at a biochemical and physiological level, often by binding to receptors. Drugs are administered through various routes including oral, parenteral, topical, inhalation, and others. Factors like dosage form, route of administration, lipid solubility, protein binding, blood supply impact the pharmacokinetic profile of a drug. Adverse effects are also an important aspect of pharmacology studied through toxicology.

1. Definitions
Pharmacology
It is the study of drugs and its action on the living organisms
Pharmacology (from Greek , pharmakon, "drug"; and logia) is the study
of drug action
Drug:
In the United States, the Federal Food, Drug, and Cosmetic Act definition of "drug"
includes "articles intended for use in the diagnosis, cure, mitigation, treatment, or
prevention of disease in man or other animals" and "articles (other than food)
intended to affect the structure or any function of the body of man or other animals."

2. DOSAGE FORMS
For administration to patients, drugs prepared in variety of pharmaceutical forms
• SYRUP
• TABLET
• CAPSULE
• SUPPOSITORY
• ENEMA
• INJECTION
• PESSARY

4. Routes of drug administration
1. Topical
On skin or mucous membrane
E.g. creams, ointment, powders, eye drops,
eardrops etc.
2. Oral (enteral)
By oral route
e.g. tablets, capsules, syrups etc.

5. Advantages of oral route
Convenient
Not painful
Disadvantages
Slow absorption and action
Cannot take bitter or irritating drugs
Drugs may be destroyed by gastric juice
Cannot be used in unconscious or vomiting patients.

6. Parenteral route
Includes all types of injections
e.g.
Intravenous- veins
Intramuscular- in muscles
Intradermal- in layers of skin
Subcutaneous- below the skin
Intra-arterial- arteries
Intraarticular- in joint cavity
Intrathecal- spinal cord meninges

7. Parenteral route
Advantages:
Faster absorption and action
Irritating drugs can be given
Can be used in unconscious or vomiting patient
Disadvantages:
Painful and inconvenient

8. Special routes
a) Sublingual (below the tongue)
Advantages
Fast absorption and quick action
No first pass metabolism
Convenient

9. Special routes
b) Rectal (through the anus)
Advantages:
Fast absorption because of good rectal blood supply
Can be used in unconscious and vomiting patients

10. Special routes
C) Inhalation
Formulations like aerosols or fumes can be used mainly for
respiratory diseases.
Drug delivery systems
e.gs.
Insulin pumps dermal patches etc.
Intended for chronic use of drugs.

11. Pharmacokinetics
It includes study of processes and its time course like absorption, distribution,
metabolism and excretion of the drugs
Steps of Pharmacokinetics:
Steps depend on formulation and route of administration
Disintegration: It is the process of breaking of tablet into small particles.
Dissolution: It means mixing with GIT water and going in to solution.
Faster is the disintegration and dissolution, faster is the absorption.

12. Drug Absorption
Transfer of drugs molecules from the G.I. tract to the blood or
circulation
Mechanisms of absorption:
a) Passive - due to conc. Gradient (High CONC to low CONC)
without spending energy
b) Active - against conc. gradient with use of energy
c) Carrier mediated - with help of protein like carrier molecule

13. Factors affecting absorption
a) Lipid solubility - since all cell membranes are mainly
made of lipids.
b) Ionization - unionized molecules are more lipid soluble
and are faster absorbed.
c) Blood supply and area of absorption
greater area and good blood supply allows faster
absorption.
d) Route of absorption - parenteral route gives better
absorption than oral route.

14. Distribution
It is the transport of drug molecules by blood to
different organs and tissues.
Drug gets distributed fluid to fluid

15. Total body fluid - 40 lits
ECF ICF
12 lits 28 lits
Volume of distribution: it is the total amount of
body fluid in which the drug is distributed in the
same concentration as in blood.

16. Factors affecting distribution
a) lipid solubility - more lipid soluble drug is distributed fast.
b) blood supply to the organs.
c) Protein binding -
Drug molecules in blood are bound to protein molecules in
blood like albumin and glycoproteins.

17. Importance of protein binding
Some drug molecules are bound and some are free
Only free drug molecules can get distributed to tissues.
Bound drug molecules cannot go to the tissue.
More the protein binding, less is the distribution.
More protein binding can also become an advantage
since drug remains in the blood for a longer period of
time.

19. Drug metabolism
It is the breakdown of drug molecule into metabolites.
Main organ of metabolism is LIVER, though other tissues can
also metabolize.
Metabolites formed may or may not be active

20. Reactions of metabolism
a) Phase I reactions:
e.g. oxidation, reduction and hydrolysis.
b) Phase II reactions:
e.g. conjugation

21. Enzymes of metabolism
Situated in the cytoplasm mainly and in the endoplasmic
reticulum.
Cytochrome P450 is the main group of drug metabolizing
enzymes.
Metabolism of one drug can be enhanced or inhibited by use
of two or more drugs.

22. First pass metabolism
Oral and other routes lead to absorption of drugs in veins which
pass through the liver before the drug enters systemic
circulation.
Liver can metabolise during this first pass before the drug goes
to other organs.
Routes like sublingual leads the drug directly to systemic blood
without going to the liver. Thus no first pass metabolism.

23. Excretion
It is the throwing out of drug with or without metabolism
Drug can be excreted as metabolites or unchanged
Organs of excretion -
kidney
GIT
Skin
Tears
Liver etc.

24. Renal excretion
Can take place in two ways
Glomerular filtration - filtrated from blood in glomerulus
Tubular secretion - secreted from blood vessels surrounding
tubules of nephron.
Clearance
It is the amount of plasma cleared off the drug in unit time

25. Important other terms
Bioavailability
Fraction or percentage of the total dose, which is absorbed in
systemic circulation.
(Intravenous route is not considered because bioavailability will
always be 100%.)

26. Important other terms
Half life
It is the time taken for 50% decrease in blood concentration of a
drug.
It tells how fast drug disappears from the body
It tells after what time should the next dose is given (dosage
frequency)

27. Important other terms
Loading dose
Initial one or two larger doses given to achieve blood conc.
Faster
Maintenance dose
Normal doses given after loading dose to maintain the effect

28. Important other terms
Cmax
Maximum concentration achieved in blood after a dose.
Tmax
Time required to achieve the maximum conc. in blood.

29. The minimum inhibitory concentration (MIC), an in-vitro
microbiological test, where the effective inhibition of
bacterial growth is measured, can be related to the
maximum concentration (Cmax) achieved in plasma, when
the antimicrobial is administered.
Minimum Bactericidal Concentration (MBC)
Minimum Inhibitory Concentration (MIC)

30. Pharmacodynamics
It is what the drug does to the body.
It is the study of biochemical and physiological actions and the
mechanism of the drugs
How do drugs act?
1) By action on enzymes
activation
Inhibition
2) by acting on receptors

31. Receptors
They are certain protein molecules at the site of action (tissue
cells), which bind to the drugs and produce action
Drug + Receptor
Drug-receptor complex
Action

32. Receptors
All tissue cells have receptors for different drugs
Receptors are specific for specific groups of drugs
Response is proportional to number of receptors occupied
Max. response when all receptors are occupied
For most of the drugs no action can be produced unless they
combine with their receptors.

33. Affinity:
It is the strength of attraction between drug and its receptor
Intrinsic activity:
It is the ability of drug to activate its receptor after binding.
Maximum efficacy:
It is the largest effect a drug can produce
Potency:
It is minimum amount of drug required to show an effect.

34. Agonist
It is the drug, which activates the receptor to produce action
Antagonist
It is the drug, which only blocks the receptor without producing
action
Types
Competitive (reversible)
Noncompetitive (irreversible)

35. ED 50:
It is the dose of drug needed to produce effect in 50% of the
population/animals tested
LD 50:
Dose needed to cause a lethal effect (mortality) in 50% of its
subjects / animals

36. Therapeutic Index
It is the margin of safety of the drug and is the ratio of dose required to
produce toxic effect & that required to produce desired therapeutic
effect
It is ratio of LD50 / ED50
It is measure of safety of a drug
TI should be always > 1
If it is less than 1, it means lethal or toxic effect is seen earlier.
Higher therapeutic index greater is the margin of safety

37. Additive effect:
Two drugs acting by same mechanism leading to increase in
response compared to individual drug.
Synergistic effect:
Two drugs acting by different mechanisms leading to
increase in response

38. DRUG TOXICOLOGY
Study of unwanted effects of the drug
Side effect:
Non-deleterious or harmless adverse effect
Toxic effect:
Harmful adverse effect

39. Types of adverse effects
a) Local : at the site of drug administration
(before absorption)
b) Systemic : adverse effect on any tissue or organ
after absorption and distribution
Teratogenicity: Drugs not to be given in pregnancy - fetal deformities
or birth deffects eg; thalidomide tragedy, isotretinoin, Ionizing
radiation, alcohol, smoking etc.
Placebo: Inactive substance used for its psychological effect on patient

40. ORGAN TOXICITIES
Hepatotoxicity : Toxicity to liver e.g. jaundice
Nephrotoxicity : Toxicity to kidney e.g. dysuria
Cardiotoxicity : Toxicity to heart e.g. increased heart rate
(tachycardia)
Oculotoxicity : Toxicity to eye e.g. double vision (diplopia)
Ototoxicity : Toxicity to ear e.g. loss of hearing

41. G.I.toxicity:
Gastrointestinal toxicity e.g. nausea, vomiting etc.
Allergic reaction:
Body produces allergic reaction towards the drug molecules.

42. Carcinogenesis:
Ability to produce cancer
Teratogenesis:
Ability to produce birth defects in fetus if
taken by pregnant women
Tolerance:
Decrease in usual response due to repeated
administration of the drug
Dependence:
Physical or psychological desire to have the
drug on continuous basis.

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