B. Optometry, 4th Semester
Basic and Ocular Pharmacology
Study Material
(Basic and Ocular Pharmacology )
_____________________________________________________________________________________
Table of Contents
1. Introduction to Pharmacology
2. Nature of drugs
3. Routes of drug administration
4. Sources of drugs
5. Dosages forms of drugs
6. Practice long / short answer questions
INTRODUCTION TO PHARMACOLOGY-
DEFINITION-
Pharmacology is the science of drugs (Greek: Pharmacon—drug; logos—discourse in). In a broad sense, it deals with interaction of
exogenously administered chemical molecules with living systems, or any single chemical substance which can produce a biological
response is a ‘drug’. It encompasses all aspects of knowledge about drugs, but most importantly those that are relevant to effective and
safe use for medicinal purpose.
The two main divisions of pharmacology are pharmacodynamics and pharmacokinetics.
Pharmacodynamics (Greek: dynamis—power) —What the drug does to the body. This includes physiological and biochemical
effects of drugs and their mechanism of action at organ system/subcellular/macromolecular levels, e.g.—Adrenaline → interaction
with adrenoceptors → G-protein mediated stimulation of cell membrane bound adenylyl cyclase → increased intracellular cyclic 3´,5
´AMP → cardiac stimulation, hepatic glycogenolysis and hyperglycaemia, etc.
Pharmacokinetics (Greek: Kinesis—movement)—What the body does to the drug. This refers to movement of the drug in and
alteration of the drug by the body; includes absorption, distribution, binding/localization/storage, biotransformation and excretion of
the drug, e.g. paracetamol is rapidly and almost completely absorbed orally attaining peak blood levels at30–60 min; 25% bound to
plasma proteins, widely and almost uniformly distributed in the body (volume of distribution ~ 1L/kg); extensively metabolized in the
liver, primarily by glucuronide and sulfate conjugation into inactive metabolites which are excreted in urine; has a plasma half-life
(t½) of 2–3 hours and a clearance value of 5 ml/kg/min.
NATURE OF DRUGS
Drug (French: Drogue—a dry herb) It is the single active chemical entity present in a medicine that is used for diagnosis, prevention,
treatment/ cure of a disease. This disease-oriented definition of drug does not include contraceptives or use of drugs for improvement
of health. The 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.” The term ‘drugs’ is being
also used to mean addictive/abused/illicit substances. However, this restricted and derogatory sense usage is unfortunate degradation
of a time-honoured term, and ‘drug’ should refer to a substance that has some therapeutic/diagnostic application.
ROUTES OF DRUG ADMINISTRATION
, Local Routes
It is the simplest mode of administration of a drug at the site where the desired action is required. Systemic side effects are minimal.
1. Topical: Drug is applied to the skin or mucous membrane at various sites for local action.
a. Oral cavity: As a suspension, e.g. nystatin; as a troche, e.g. clotrimazole (for oral candidiasis); as a cream,
e.g. acyclovir (for herpes labialis); as ointment and jelly, e.g. 5% lignocaine hydrochloride (for topical anaesthesia); as a spray, e.g.
10% lignocaine hydrochloride (for topical anaesthesia).
a. GI tract: As tablet that is not absorbed, e.g. neomycin (for sterilization of gut before surgery).
b. Rectum and anal canal: i. As an enema (administration of drug into the rectum in liquid form): – Evacuant enema (for
evacuation of bowel): For example, soap water enema—soap acts as a lubricant and water stimulates the rectum. –
Retention enema: For example, methylprednisolone in ulcerative colitis. ii. As a suppository (administration of the drug in a
solid form into the rectum), e.g. bisacodyl— for evacuation of bowels.
c. Eye, ear and nose: As drops, ointments and sprays (for infection, allergic conditions, etc.), e.g. gentamicin eye/ear drops.
d. Bronchi: As inhalation, e.g. salbutamol, ipratropium bromide, etc. (for bronchial asthma and chronic obstructive pulmonary
disease).
e. Skin: As ointment, cream, lotion or powder, e.g. clotrimazole (antifungal) for cutaneous candidiasis.
1. Intra-arterial route: This route is rarely employed. It is mainly used during diagnostic studies such as coronary angiography
and for the administration of some anticancer drugs, e.g. for treatment of malignancy involving limbs.
2. Administration of the drug into some deep tissues by injection, e.g. administration of triamcinolone directly into the joint
space in rheumatoid arthritis.
Systemic Routes
Drugs administered by this route enter blood and produce systemic effects.
1. Oral Route
It is the most common and acceptable route for drug administration. Dosage forms are tablet, capsule, syrup, mixture, etc., e.g.,
paracetamol tablet for fever, omeprazole capsule for peptic ulcer are given orally.
Advantages Disadvantages
Convenient and easy to administer – Can be self-
Slow onset of action – Not suitable for emergencies.
administered without medical assistance.
First-pass metabolism – Some drugs are inactivated by
Safe and non-invasive – No risk of infection or pain as
liver metabolism (e.g., nitroglycerin).
compared to injections.
Not suitable for unconscious or vomiting patients – Risk of
Economical – Cheaper dosage forms and no need for
aspiration.
sterile equipment.
Gastrointestinal irritation – Drugs like aspirin may cause
Suitable for long-term therapy – Ideal for chronic
gastric irritation or ulcers.
conditions (e.g., diabetes, hypertension).
Variable absorption – Affected by food, gastric pH,
Wide variety of dosage forms available – Tablets, capsules,
motility, and disease conditions.
syrups, suspensions, etc.
Unsuitable for drugs destroyed by gastric acid or enzymes
Good patient compliance – Most acceptable route,
– e.g., insulin, certain antibiotics.
especially for out-patients.
1. Sublingual Route
The preparation is kept under the tongue. The drug is absorbed through the buccal mucous membrane and enters the systemic
circulation directly, e.g. nitroglycerin for acute anginal attack and buprenorphine for myocardial infarction.
Basic and Ocular Pharmacology
Study Material
(Basic and Ocular Pharmacology )
_____________________________________________________________________________________
Table of Contents
1. Introduction to Pharmacology
2. Nature of drugs
3. Routes of drug administration
4. Sources of drugs
5. Dosages forms of drugs
6. Practice long / short answer questions
INTRODUCTION TO PHARMACOLOGY-
DEFINITION-
Pharmacology is the science of drugs (Greek: Pharmacon—drug; logos—discourse in). In a broad sense, it deals with interaction of
exogenously administered chemical molecules with living systems, or any single chemical substance which can produce a biological
response is a ‘drug’. It encompasses all aspects of knowledge about drugs, but most importantly those that are relevant to effective and
safe use for medicinal purpose.
The two main divisions of pharmacology are pharmacodynamics and pharmacokinetics.
Pharmacodynamics (Greek: dynamis—power) —What the drug does to the body. This includes physiological and biochemical
effects of drugs and their mechanism of action at organ system/subcellular/macromolecular levels, e.g.—Adrenaline → interaction
with adrenoceptors → G-protein mediated stimulation of cell membrane bound adenylyl cyclase → increased intracellular cyclic 3´,5
´AMP → cardiac stimulation, hepatic glycogenolysis and hyperglycaemia, etc.
Pharmacokinetics (Greek: Kinesis—movement)—What the body does to the drug. This refers to movement of the drug in and
alteration of the drug by the body; includes absorption, distribution, binding/localization/storage, biotransformation and excretion of
the drug, e.g. paracetamol is rapidly and almost completely absorbed orally attaining peak blood levels at30–60 min; 25% bound to
plasma proteins, widely and almost uniformly distributed in the body (volume of distribution ~ 1L/kg); extensively metabolized in the
liver, primarily by glucuronide and sulfate conjugation into inactive metabolites which are excreted in urine; has a plasma half-life
(t½) of 2–3 hours and a clearance value of 5 ml/kg/min.
NATURE OF DRUGS
Drug (French: Drogue—a dry herb) It is the single active chemical entity present in a medicine that is used for diagnosis, prevention,
treatment/ cure of a disease. This disease-oriented definition of drug does not include contraceptives or use of drugs for improvement
of health. The 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.” The term ‘drugs’ is being
also used to mean addictive/abused/illicit substances. However, this restricted and derogatory sense usage is unfortunate degradation
of a time-honoured term, and ‘drug’ should refer to a substance that has some therapeutic/diagnostic application.
ROUTES OF DRUG ADMINISTRATION
, Local Routes
It is the simplest mode of administration of a drug at the site where the desired action is required. Systemic side effects are minimal.
1. Topical: Drug is applied to the skin or mucous membrane at various sites for local action.
a. Oral cavity: As a suspension, e.g. nystatin; as a troche, e.g. clotrimazole (for oral candidiasis); as a cream,
e.g. acyclovir (for herpes labialis); as ointment and jelly, e.g. 5% lignocaine hydrochloride (for topical anaesthesia); as a spray, e.g.
10% lignocaine hydrochloride (for topical anaesthesia).
a. GI tract: As tablet that is not absorbed, e.g. neomycin (for sterilization of gut before surgery).
b. Rectum and anal canal: i. As an enema (administration of drug into the rectum in liquid form): – Evacuant enema (for
evacuation of bowel): For example, soap water enema—soap acts as a lubricant and water stimulates the rectum. –
Retention enema: For example, methylprednisolone in ulcerative colitis. ii. As a suppository (administration of the drug in a
solid form into the rectum), e.g. bisacodyl— for evacuation of bowels.
c. Eye, ear and nose: As drops, ointments and sprays (for infection, allergic conditions, etc.), e.g. gentamicin eye/ear drops.
d. Bronchi: As inhalation, e.g. salbutamol, ipratropium bromide, etc. (for bronchial asthma and chronic obstructive pulmonary
disease).
e. Skin: As ointment, cream, lotion or powder, e.g. clotrimazole (antifungal) for cutaneous candidiasis.
1. Intra-arterial route: This route is rarely employed. It is mainly used during diagnostic studies such as coronary angiography
and for the administration of some anticancer drugs, e.g. for treatment of malignancy involving limbs.
2. Administration of the drug into some deep tissues by injection, e.g. administration of triamcinolone directly into the joint
space in rheumatoid arthritis.
Systemic Routes
Drugs administered by this route enter blood and produce systemic effects.
1. Oral Route
It is the most common and acceptable route for drug administration. Dosage forms are tablet, capsule, syrup, mixture, etc., e.g.,
paracetamol tablet for fever, omeprazole capsule for peptic ulcer are given orally.
Advantages Disadvantages
Convenient and easy to administer – Can be self-
Slow onset of action – Not suitable for emergencies.
administered without medical assistance.
First-pass metabolism – Some drugs are inactivated by
Safe and non-invasive – No risk of infection or pain as
liver metabolism (e.g., nitroglycerin).
compared to injections.
Not suitable for unconscious or vomiting patients – Risk of
Economical – Cheaper dosage forms and no need for
aspiration.
sterile equipment.
Gastrointestinal irritation – Drugs like aspirin may cause
Suitable for long-term therapy – Ideal for chronic
gastric irritation or ulcers.
conditions (e.g., diabetes, hypertension).
Variable absorption – Affected by food, gastric pH,
Wide variety of dosage forms available – Tablets, capsules,
motility, and disease conditions.
syrups, suspensions, etc.
Unsuitable for drugs destroyed by gastric acid or enzymes
Good patient compliance – Most acceptable route,
– e.g., insulin, certain antibiotics.
especially for out-patients.
1. Sublingual Route
The preparation is kept under the tongue. The drug is absorbed through the buccal mucous membrane and enters the systemic
circulation directly, e.g. nitroglycerin for acute anginal attack and buprenorphine for myocardial infarction.
