General Pharmacology

General Pharmacology III B.Pharm Class Notes
Dr.KPS Gowda

1. Pharmacology I (T) 1.General Pharmacology (21h) III B.Ph (RS3) 2015-16 Dr.KPS Gowda Page 1

III B.Pharm (RS3) 2015-16 Pharmacology I (Theory) 75h
1.General Pharmacology (21h)
a.Introduction and definitions-Sources and active ingredients of drugs. (1h)
Pharmacology- Pharmacology is derived from two Greek words- Pharmacon (drug), logos (a
discourse or treatise) - It is a science that deals with drugs. It includes a detailed study of the
history, properties, physiological effects, mechanism of action, absorption, distribution,
metabolism, excretion and uses of a drug.
Drug- The word drug derived from French word- Drogue ( a dry herb). A drug is defined as
any substance which is used to cure, diagnose or prevent a disease.
Divisions of Pharmacology-
a. Materia Medica- It is the study of preparation, properties, uses and effects of a drug. It is
an old branch of Pharmacology.
b.Pharmacokinetics- (What the body does to a drug?). It is the study of absorption,
distribution, metabolism and elimination (ADME) of drugs.
c.Pharmcodynamics- (What a drug does to the body?) It is the study of the biochemical and
physiological effects of drugs and their mechanisms of action.
d.Neuropharmacology- It is the study of the effects of drugs on CNS and ANS functioning.
e.Psychopharmacology- It is the study of the effects of drugs on mood, sensation, thinking
and behaviour.
f.Pharmacogenetics- It is the study of unusual effects of drug produced in individuals with
gene defect.
g.Pharmacogneomics - It is the study of the role of genetics in drug response.
h.Pharmacoepidemiology- It is the study of the effects of drugs in large number of people.
i.Dental Pharmacology- It is the study of drugs commonly used in the treatment of dental
disease.
j.Posology- It is the study of dosages of drugs.
k. Clinical Pharmacology- It is the scientific study of drugs in man. The efficacy and safety
of a drug is studied in patients and healthy volunteers.
l. Chemotheraphy- It deals with the effects of drugs on micro-organisms and parasites which
occur in a living organism. It also includes the treatment of cancer.
m. Toxicology- It deals with poisonous effects of drugs, detection of poison and its
treatment.
Sources and active ingredients of drugs-

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a. Plant drugs - The following is the list of plant drugs and sources.
Quinine- Cinchona bark
Vincristine- Vinca plant
Digoxin, digitoxin- Digitalis purpura
Morphine- Papaver somnifera
Atropine- Atropa belladonna
Nicotine- Tobacco
Caffeine- Coffee, tea
b. Drugs from microorganisms- Many life-saving drugs are obtained from fungi, moulds
and bacteria e.g. penicillin from Penicillium notatum, chloramphenicol from Streptomyces
venezuelae, grisofulvin (an anti-fungal drug) from Penicillium griseofulvum, neomycin from
Streptomyces fradiae and streptomycin from Streptomyces griseus.
b. Animal drugs- Some drugs are still obtained from animal source. For example: Insulin,
extracted from pork and beef pancreas, is used for the treatment of diabetes mellitus. Thyroid
powder is used for treating hypothyroidism. Heparin is used as an anticoagulant. Hormones
are used as replacement therapy. Vaccines (cholera, T.B., smallpox, polio) and sera
(antidiptheria and antitetanus) are used for prophylaxis/treatment.
c. Mineral drugs- Minerals (naturally occurring inorganic solid substances with chemical
formula) or their salts are useful therapeutic agents. For example: Ferrous sulphate is used in
iron deficiency anaemia. Magnesium sulphate is employed as purgative. Magnesium
trisilicate, aluminium hydroxide and sodium bicarbonate are used as antacids for hyperacidity
and peptic ulcer. Kaolin (aluminium silicate) is used to treat diarrhoea. Radioactive isotopes
of iodine, phosphorus, gold are employed for the diagnosis/ treatment of diseases particularly
malignant conditions.
d. Synthetic drugs- At present majority of drugs used are prepared synthetically, such as
aspirin, oral anti-diabetics, antihistamines, amphetamine, chloroquine, chlorpromazine,
general and local anaesthetics, paracetamol, phenytoin, synthetic corticosteroids,
sulphonamides and thiazide diuretics. Advantages of synthetic drugs are: They are
chemically pure. The process of preparing them is easier and cheaper. Control on the quality
of the drug is excellent.
e. Drugs from DNA recombinant technology- Hepatitis vaccine, human insulin.
The following are the various active ingredients of drugs.
a. Alkaloids- Alkaloids are a group of naturally occurring chemical compounds that contain
mostly basic nitrogen atoms. Eg.Caffeine, atropine, morphine, quinine. Alkaloids are basic

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substances, and combine with an acid to form salt. These salts are soluble in water and are
used in medicine. Eg Caffeine citrate, morphine sulphate, atropine sulphate, quinine sulphate.
b. Glycosides- Glycosides are a class of molecules in which, a sugar molecule (glycon) is
bonded (ether linkage) to a “non-sugar” (aglycone/genin) molecule. The glycone part is
essential for the pharmacokinetic aspect of aglycone. The aglycone part is responsible for the
pharmacological effect. Eg. Digitoxin, digoxin, sennoside A, quabain.
c. Oils –Oil is a non-polar neutral viscous liquid. In plants oils are present in the following
forms-
Volatile oil (essential oil)- Volatile oil is a concentrated hydrophobic liquid containing
volatile aroma compounds from plants. Eg-Peppermint oil, clove oil, ginger oil, eucalyptus
oil.
Fixed oil- These are the glycerides of oleic acid, palmitic acid and stearic acid. Eg. Olive oil,
castor oil, cotton seed oil. Fixed oils from animal source are cod liver oil, shark liver oil,
butter.
Waxes- Waxes are composed of fatty acids combined with monohydric alcohol. Eg. Wax,
beeswax.
Mineral Oil- These are mixture of hydrocarbons obtained by fractional distillation. Eg. Hard,
soft and liquid paraffin. Hard and soft paraffin are used as ointment bases and liquid paraffin
is used as laxative.
d.Tannins- These are non-nitrogenous plant constituents, and have an astringent action. Eg-
Pyrogallol tannins (occur in oak apple), pyrocatechol tannins (occur in eucalyptus).
e.Gums- They are exudates of plants. Chemically they are polysaccharides, and on
hydrolysis yield simple sugars. Eg- Agar, tragacanth.
f.Resins- Resin is a hydrocarbon secretion of many plants. Resins are produced by oxidation
and polymerization of volatile oils. Eg. Oleoresin, gum-resin (asafoetida), myrrh, balsams
(benzoin).
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b.Routes of drug administration (1h)
A route of administration in Pharmacology and Toxicology is the path by which drugs, fluid,
poison, and other substance is taken into the body.
Routes can be broadly divided into those for a) Local action and b) Systemic action.
I.Local routes-The drugs are applied locally for local effects. Systemic absorption of the
drug from these routes is minimal or absent. Hence systemic side effects or toxicity are
absent or minimal.

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1.Topical- This refers to external application of the drug to the surface for localized effect.
a.Skin- Drug is applied as ointment, cream, lotion, paste, powder, dressing, spray, etc.
b.Mucous membrane-
Mouth and pharynx- As paint (Mandle’s paint), lozenges (strepsils), mouth washes and
gargles (povidone iodine gargle).

Eyes, ear and nose- As drops, ointments, irrigation, nasal spray, Otrivin nasal spray to
reduce nasal congestion. chlopamphenicol eye ointment.

Gastrointestinal tracts- Non absorbable drugs are given orally. Magnesium hydroxide,
sucralfate, neomycin.
Bronchi and lungs- As inhalations, aerosols- e.g. salbutamol, cromolyn sodium.

Urethra- As jellies E.g. Lidocaine (xylocaine)- For the surface anaesthesia of male or female
urethra.

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Vagina- As pessaries-(clotrimazole vaginal pessaries), vaginal tablets (estrogens vaginal
tablets), Vaginal inserts (spermicide), Vaginal creams (ovestin), vaginal douches (betadine
vagina douche).

Vaginal douche
Anal canal- Ointment (nitro glycerin anal ointment), suppositories- (hydrocortisone
suppositories).

2. Deeper tissues- Using syringe and needle drug is administered to deeper tissues, but the
drug is not absorbed into systemic blood circulation.
Intra-articular injections- Long term intra-articular hydrocortisone injection in
osteoarthritis.
Intrathecal injection- Intrathecal administration of vincristine in cancer chemotherapy.

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Retrobulbar injection- Injection in to the space behind the globe of eye balls. Ocular
anaesthesia for cataract surgery.
3.Arterial supply- Intra-arterial route is used in angiography- Angiography is the x-ray
(radiographic) study of the blood vessels. An angiogram uses a radio-opaque substance, or
contrast medium, to make the blood vessels visible under x ray- cerebral, pulmonary,
coronary, renal angiography.
II Systemic routes-
1. Oral Route: - In this route the drug is placed in the mouth and Swallowed. It is also called
per oral (p.o.). The solid dosage forms- tablets, capsules, powders, spansules, moulded tablets
and liquid dosage forms- syrups, mixtures, elixirs, emulsions, etc can be given orally.
Advantages of oral route
a. Convenient - Can be self administered, Pain free, easy to take
b. Absorption - Takes place along the whole length of the gastro intestinal tract.
c. Cheap - Compared to most other parenteral routes
Disadvantages of oral route
a. Action is slower and thus not suitable for emergencies.
b. Unpalatable drugs-e.g. paraldehyde are difficult to administer.
c. May cause nausea and vomiting.(e.g. emetine)
d. Not suitable for uncooperative/un-conscious/vomiting patients.
e. Some drugs are destroyed by gastric juice- e.g. insulin, vasopressin.
f. Sometimes inefficient - only part of the drug may be absorbed
g. First-pass effect- drugs absorbed in to the liver by portal circulation and get metabolized
before entering into the systemic circulation.

2. Sublingual or buccal route-The tablet or pellet containing the drug is placed under the
tongue or crushed in the mouth and spread over the buccal mucosa. It is not swallowed. The
drug is absorbed from the buccal mucosa. Drugs given sublingually are- nitroglycerine,
methyltestosterone, isoprenaline, clonidine.

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Advantages-
a. Quick absorption and action.
b. Drug enters directly into blood circulation.
c. No first pass metabolism. (FPM).
d. Action can be terminated by spitting out the tablet.
e. No drug destruction by the gastric juice.
Disadvantages-
a. Not available for all drugs.
b. All drugs are not absorbed by this route.
c. Not suitable for unpalatable drugs.
3.Rectal route of administration- Certain irritant and unpleasant drug can be put into
rectum as suppositories or retention enema for systemic effect. It is preferred for the patient
with recurrent vomiting. Drugs given rectally are – aminophylline, indomethacin,
paraldehyde, diazepam, etc.
4. Transcutaneous- Highly lipid soluble drugs can be applied over the skin for slow and
prolonged absorption. It is further classified as
a.Iontophoresis- It is a technique of introducing ionic medicinal compounds into the body
through the skin by applying a local current. e.g.salicylates. Anode iontophoresis is used for
positively charged drugs and cathode iontophoresis is used for negatively charged
compounds. The force of repulsion between similar charges drives the drug deep into the
tissues.

Iontophoresis Jet injection

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b.Inuction- It is rubbing the drug on the skin. The drug gets absorbed and produces systemic
effects. E.g. nitroglycerin ointment for angina.
c. Jet injection- This method does not require a syringe. So it is painless. Using a gun like
instrument with a micro-fine orifice, the drug solution is projected as a high velocity jet
(dermojet). This method is useful for mass inoculation.
d.Adhesive patches-It is a transdermal preparation. It is available in the form of adhesive
unit. It delivers the drug slowly. So it produces prolonged systemic effect. E.g. belladona
plaster.

Adhesive patch
5.Inhalation-Volatile liquids and gases are given by inhalation for systemic action. The
drugs administered by this route are- general anaesthetics, amylnitrite.
6.Parenteral route of administration. (par-beyond, enteral-intestinal)
In this route of administration the drug does not pass through the gastrointestinal tract. It
directly reaches to the blood. The drugs are administered by injections. Injections can be
given in many different ways e.g.intradermal (id), subcutaneous(sc), intramuscular (im),
intravenous(iv), intraperitoneal (ip),etc.
Advantages-
1. Injections can be given even in unconscious, uncooperative patients.
2. Quick absorption-hence suitable in emergencies.
3. There is no GIT related problems.
4. Dose requirement is less compared to oral route.
5. Accurate dose adjustment is possible.
6. No first pass metabolism.
7. Drugs having unpleasant smell or taste can be given.
Disadvantages-
1. Inconvenient- injections can be painful, costly.
2. Tissue injury, inflammation and may cause infection.
3. Costly.

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4. Self medication is difficult.
5. Withdrawal of the drug is not possible.

a.Intradermal injection (id)- Only 0.1 to 0.2ml can be administered by id route. The drug is
injected into the layers of the skin. It is painful. E.g. vaccines (BCG vaccine), test dose of
drugs (penicillin), are given by id injections.

Intradermal inj SC inj IM inj
b. Subcutaneous injection (sc)- A subcutaneous injection is an injection administered into
the fatty area just under the skin. Absorption from sc route is slow but steady. SC injection
should not be given in patients with shock, because during shock, blood flow to subcutaneous
tissue is reduced. Drugs usually given by sc route are insulin, adrenaline, and local
anaesthetics.
c. Intramuscular injection (im)- In this route of administration the drug is given into the
skeletal muscles like deltoid, triceps etc. Drug once reaches to the muscles, absorbs into the
blood. Mild irritant or non-irritant drugs can be administered as there is less supply of sensory
nerves. But muscles are more vascular, hence absorption is faster. Up to 5ml can be given by
im route. Eg many vaccines and antibiotics are administered by IM route.
d. Intravenous injection (iv) - After iv injection drug enters directly in to the blood and goes
to the heart. Large volume can be given. Onset of action is very quick and the bioavailability

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is 100%. The dose requirement is small. Withdrawal of the drug is not possible. E.g
cimetidine, ampicillin, digoxin inj etc.

IV inj IP inj to mouse
e.Intra peritoneal (ip)- In this route the drug is injected in to the peritoneal cavity. By this
route fluids like glucose and saline can be given to the children. It is also used for peritoneal
dialysis. It is one of the common routes for administering the drugs to rats and mice.
Newer methods and devices for drug delivery.
1. Occusert and progestasert- Occusert is a device that is placed under the eyelid. It contain
pilocarpine, the drug is absorbed slowly from the conjunctiva. It is used in the treatment of
glaucoma. Progestasert is an intrauterine device that contains progestin. The drug is released
slowly over several months.
2. Subcutaneous contraceptive implants.

SC contraceptive implant Drug carrier-liposome

3. Targeted delivery system- Drug is attached to a carrier-liposome. The carrier takes the
drug to the site of action. This method is useful in anticancer drugs. Anti-cancer drugs are
highly toxic. To prevent the toxic effect of these drugs on healthy cells and to deliver the drug
directly to the cancer cells, this method is useful.
4. Slow /sustained release (SR) preparations. The SR tablets are given special coating to
ensure slow and sustained release. This avoids the frequent dosage of a drug.

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5. Metered dose inhaler (MDI)- It is a device that releases a fixed quantity of the drug in an
aerosol form each time when the button is pressed.

MDI Nebulizer
6. Rotahaler- This is the device used for delivering micro-fined powder.
7. Nebulizer-It is a device that generates very fine particles (about 0.3 to 0.5 microns) of the
drug in the form of mist.
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c. Absorption of drug. Factors affecting drug absorption-(2h)
Absorption is the movement of a drug into the blood circulation. It is considered that
intravenous route does not involve absorption, and there is no loss of drug. Hence the
bioavailability is 100%. Drug administration by other routes may result in only partial
absorption and thus, lower bioavailability.
Passage of drug across cell membrane- The cell membrane acts as a biological barrier. The
following are the processes by which a drug can cross biological membrane.
1.Passive transport and 2. Specialized transport.
1.Passive transport- This transport is energy independent and no utilization of ATPs. The 4
types of passive transports are diffusion, facilitated diffusion, filtration and osmosis.
a. Diffusion (simple)- Diffusion is the net movement of drug molecules from an area of high
concentration to an area with lower concentration. The difference of concentration between
the two areas is termed as the concentration gradient, and diffusion will continue until this
gradient has been eliminated. Diffusion across the cell membrane depends on concentration
gradient and lipid solubility. Lipid solubility depends on ionization. Un-ionized drugs are
more lipid soluble and are better absorbed (more reabsorbed in the kidneys and less
excreted). Ionized drugs are less lipid soluble and are less absorbed (less reabsorbed in
kidneys and more excreted). Ionization depends on pH of drug and pH of the medium
(surrounding fluid). If the pH is the same the drug remain unionized and become more lipid

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soluble and absorbed better. (e.g. acidic drugs like aspirin, barbiturates, etc. are better
absorbed from the stomach. Weakly alkaline drugs like morphine, atropine, chloroquine are
better absorbed from the small intestine.
If pH is apposite-> drug is ionized-> less lipid soluble-> less absorption (e.g. alkaline drugs
are poorly absorbed in the stomach).
.
b.Facilitated diffusion (carrier- mediated diffusion)- It is the movement of drug molecules
across the cell membrane via special transport proteins that are embedded within the cellular
membrane. Many large molecules, such as glucose, are insoluble in lipids and too large to
pass through the membrane pores. Therefore, it will bind with its specific carrier proteins,
and moved through the cellular membrane.

Facilitated diffusion
Glomerular filtration
c. Filtration- Filtration is movement of water and drug molecules across the cell membrane
due to hydrostatic pressure generated by the CVS. Depending on the size of the membrane
pores, filtration takes place. For example, the membrane pores of the Bowman’s capsule in
the kidneys are very small and only albumin (the smallest protein) may pass through these
pores. The membrane pores of liver cells are large, most of the drugs pass through these pores
and they get metabolized. Capillaries in the CNS have tight junctions called BBB.

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d.Osmosis- Osmosis is the movement of water molecule through the cell membrane (semi
permeable membrane) from the region of higher water concentration to the region of less
water concentration is called osmosis.

2.Specialized transport- Specialized transport of drug across the cell membrane requires
carrier proteins. The drug forms a complex with the carrier proteins at the outer surface of the
cell membrane and then transported across the cell membrane to the inner surface and the
drug is released from the drug carrier complex. These are of two main types- active transport,
and endocytosis.
a. Active transport- In active transport, the drug molecule penetrates in the lipid bilayer
membrane from lower concentration to the higher concentration of solutes against the
concentration gradient with the expenditure of energy and with the help of carrier proteins.
There are two types - Primary active transport and secondary active transport.
Primary active transport-(direct active transport). It directly uses energy to transport
molecules across a membrane. The energy used in this type of active transport is ATP. The
ions Na
+
, K
+
, Ca
2+
and H
+
are transported by primary active transport using carrier protein
and ATP.

Secondary active transport- (co-transport) In secondary active transport, a molecule is
moved down its electrochemical gradient as another is moved up its concentration gradient.

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There is no direct coupling of ATP. Examples - Sodium-proton or sodium –calcium co
transporters.
c.Endocytosis- Endocytosis is the movement of materials into a cell via membranous
vesicles. Endocytosis require the expenditure of energy (ATP). There are 3 types-
phagocytosis, pinocytosis and receptor mediated endocytosis.
Phagocytosis- Phagocytosis is also known as cell eating. This transport is utilized by large
molecular weight drugs e.g. Uptake of vit B12 along with intrinsic factor.
Pinocytosis- Pinocytosis is also known as cell drinking. This process requires a lot of energy
in the form of ATP. Fat soluble vitamins, folic acid enter the cells by pincytosis.
Receptor mediated endocytosis- It is also called clathrin-dependent endocytosis. The
receptor present on the cell membrane binds with the specific ligand. This ligand-receptor
gets ingested using clathrin molecules.

Factors affecting drug absorption-