2. CHAPTER-1
Content to Be covered:
• Introduction to Pharmacology
Scope and Applications of Pharmacology
• Routes of Administration
Advantages & Disadvantages
• Various Process of Absorption of Drugs and Factors affecting them:
Absorption
Distribution
Metabolism
Excretion
• Mechanism of Drug Action & Factors which alter or modify drug action:
Receptor Mediated
Non-Receptor Mediated
3. Here some questions arises in our mind!!
What is Pharmacy or Pharmaceutical Sciences?
Why to study Pharmacology?
What is Pharmacology?
To study and understand Pharmacology, first we should be knowing what is Pharmacy!!!
WHO defines drug as ‘any substance or product that is used or intended to use to modify or explore
physiological system or pathological states for the benefit of the recipient’.
Pharmacy can be defined as the art and study of specialized sciences inventing, compounding and
dispensing of drugs or preparing suitable dosage forms for administration of drugs to man or
animals. It includes collection, identification, purification, isolation, synthesis, standardization and
quality control of medicinal substances for their proper utilization.
So, to know drugs better to and practice different aspect of Pharmacy it is mandatory to have
knowledge of specialized particular branch of science called as “Pharmacology”.
4. Pharmacology is the science that deals with the effect of drugs on living systems. In a broad sense,
it deals with the interaction of exogenously administered chemical molecules (drugs) with the living
systems.
It consists of all aspects of knowledge about drugs, but most importantly those aspects that are
relevant to effective and safe use for medicinal purpose.
The two main Bifurcations of Pharmacology are:
1. Pharmacodynamics
2. Pharmacokinetics
5. Pharmacodynamics is the study of Physiological and Biochemical effects of drugs and their
mechanism of action in living organisms at different cellular, sub-cellular and organ system levels.
In brief, we can say after intake of the drugs whatever drug does to body at different levels comes
under Pharmacodynamics.
Pharmacokinetics is the study of movement of drugs in and alteration of the drugs by the body
which includes Absorption, Distribution, Binding/Localization/Storage,
Metabolism/Biotransformation and Excretion of the drugs. In brief, we can say “ After the intake of
drugs from the inward movement till excretion of the drugs whatever body does with the drug at
different levels is defined as pharmacokinetics.
What is TOXICOLOGY?
It is the branch of pharmacology which deals with the study of poisonous effects of drugs and other
chemicals/poisons with emphasis on their detection, prevention and treatment. It also includes the
study of adverse effects of drugs, since the same substance can be a drug or poison depending on
the dose.
6. SCOPE & APPLICATIONS:
• Inevitable for drug discovery and investigation for potential identified molecules.
• Provide explanation for mechanism of action and pharmacological action of the drug.
• Provide explanation for different drugs having related pharmacological action.
• Provide explanations about drug toxicity and drug interactions.
• Explain the action of various drugs on the various organs in the body when they are in a diseased state, with
side effects, contraindications, etc.
• For medical practitioners, knowledge of pharmacology and toxicology is necessary for prescription of most
suitable and correct dosage regimen for a diseased condition.
• Help to assess data obtained from pre-clinical studies and correlate it with pre-clinical procedures.
• With pre-clinical findings moving ahead toward clinical studies and correlate with clinical conditions.
• Post –market pharmacological results of drugs made it possible to update adverse drug reactions profiles of
various drugs.
7. What is Therapeutics, Pharmacotherapeutics and Clinical
Pharmacology?
To understand pharmacology in more precise and better way we have to go through various other aspects
related to it.
Therapeutics is that branch of medical science which deals with the treatment of diseases. In
pharmacology, therapeutics accordingly refers to the use of drugs and the method of their administration
in the treatment of disease.
Pharmacotherapeutics is the application of pharmacological information together with knowledge of the
altered physiology in the diseases for their prevention, mitigation or cure. Selection of the most appropriate
drugs, dosage and duration of the treatment taking into account the clinical indications of a patient are the
major areas of Pharmacotherapeutics.
Clinical Pharmacology is the scientific study of drugs in human beings which includes pharmacodynamic
and pharmacokinetic investigations both in healthy volunteers and patients. Evaluation of efficacy and
safety of drugs along with comparative trials of different forms of treatment are the major areas of Clinical
Pharmacology.
8. The need of clinical pharmacology is to generate optimum data for safe and effective use of drugs and the
practice of “evidence based medicine”.
Chemotherapy is the treatment of systemic infection/malignancy with specific drugs that have selective
toxicity for the infective organism/malignant cells with no or minimal effects on the host cells.
Receptor is defined as a macromolecule or binding site/platform located on the surface or inside the
effector cells that serves to recognize the signal molecule /drug and initiate the response to it, but itself
has no other function.
What is an Agonist?
An agent which activates a receptor to produce an effect similar to that of physiological signal molecule is
called as Agonist.
What is an Antagonist?
An agent which prevents the action of an agonist on a receptor or the subsequent response, but does not
have any effects of its own is called as Antagonist.
9. What is Affinity?
The ability of a drug to get bound to the receptors is called is called affinity of a drug for the receptor.
What is Efficacy or Intrinsic Activity?
The ability of a drug to initiate a pharmacological response after combining with the receptor is called
the efficacy or intrinsic activity of a drug.
DRUG NOMENCLATURE
Drugs generally have three categories of names:
Chemical Names
Non-proprietary Names
Proprietary (Brand) Names
Chemical name of the drug describes the substance chemically, eg 1- (Isopropylamino)-3-(1-
naphthoxy) propan-2-ol for Propranolol. But these names are not suitable for the purpose of
prescription.
10. Non-proprietary names are those which are accepted by a competent scientific body/authority. For ex.
United States Adopted Name (USAN) by USAN Council. The non-proprietary names of newer drugs are
kept uniform by an agreement to use the recommended International Non-Proprietary (rINN) in all
member countries of WHO to avoid confusion.
Proprietary (Brand) Names are the names assigned by the manufacturer(s) and is his property trade mark.
One drug may have multiple brand names, ex. Altol, Atcardil, Atecor for Atenolol from different
manufacturers.
Orphan drugs are those drugs or biological products for diagnosis/treatment/prevention of a rare
disease or condition for which there is no reasonable expectation that the cost of developing and
marketing it will be recovered from the sales of that drug.
Authentic Sources of Drug Information/ Standard Drugs:
Pharmacopoeia’s
Formulary’s
Physician’s Desk Reference
Textbooks & Journals of Pharmacology
11. What is Pharmacopoeia?
It is a book which contains a list of established & officially approved drugs with description of their
physical and chemical characteristics and tests for their identification , purity, methods of storage etc.
Indian Pharmacopoeia (IP)
British Pharmacopoeia (BP)
European Pharmacopoeia (EP)
United States Pharmacopoeia (USP)
Japanese Pharmacopoeia (JP)
Pharmacopoeia of People’s Republic of China (ChP)
International Pharmacopoeia (Ph.Int.)
What is Formulary/National Formulary?
It is a book that provides information about the available drugs in a country-their use, dosage, adverse
effects, contraindications, precautions, warnings and guidance on selecting the right drug for a range of
diseased conditions.
12. ROUTES OF ADMINISTRATION OF DRUGS
Route of administration is a way of getting a drug onto or into the body of living system.
Many factors determine the choice of route of administration:
• EASE OF ADMINISTRATION/CONDITION OF THE PATIENT
• PHYSICAL & CHEMICAL PROPERTIES OF THE DRUG
• PATIENT COMPLIANCE
• SITE OF ACTION
• ONSET OF ACTION
• DURATION OF ACTION
• QUANTITY OF DRUG
• METABOLISM BY THE LIVER OR EXCRETION BY THE KIDNEY
• TOXICITY
14. LOCAL ROUTES
• These routes can only be used for localized or specific areas at accessible sites and for drugs whose
systemic absorption from these sites is minimal.
• Medications of local routes are meant for their action at the site of application, thus high concentrations
are attained at the desired site without exposing the rest of the body.
• Systemic side effects or toxicity are consequently minimal from these routes of administration of drugs.
• Skin-topical, intranasal, ocular drops, mucosal-throat, mouth, ear, vaginal; these all routes in local
administration refers to external application of the drug to the surface for localized action.
• These routes are often more convenient and encouraging to the patients.
• Drugs can be efficiently delivered to localized areas on skin, oropharyngeal/nasal mucosa, eyes, ear canal,
anal canal or vagina in the form of lotion, ointment, cream, powder, rinse, paints, drops, sprays, lozenges,
suppositories or pesseries.
15. ADVANTAGES OF LOCAL ROUTES:
• These routes provides easy administration of drugs.
• Local application is useful when site specific effect of drug is required.
• There is less possibility of systemic absorption of the medicament.
• No special skill or apparatus is required in most of the cases.
DIS-ADVANTAGES OF LOCAL ROUTES:
• Drugs in the form of aqueous solution are sometimes absorbed into the blood stream and may produce
undesirable effects.
• The drugs like eye drops may penetrate into the anterior chamber and affect ciliary muscles, e.g. Cocaine.
• In some cases, specialized expertize and instruments are required.
• All drugs can’t be administered from this route.
16. ORAL ROUTE
In this route the drug is paced in oral cavity and is swallowed along with water or milk etc.
ADVANTAGES OF ORAL ROUTE
• No special skill is required for drug administration.
• Most convenient route of administration.
• Most cheaper and painless rote of administration.
• Sterilisation is not required for the preparations taken orally.
• Large quantity of drugs can be administered by this route.
• A variety of types of formulations can be administered from oral route of drug administration.
• Convenient for repeated and prolonged use and can be self- administered.
17. DISADVANTAGES OF ORAL ROUTE
• Onset of action is slow.
• Oral route is not useful in clinical emergencies.
• Oral route is not useful in cases of unconscious and non-cooperative patients.
• Drugs which get destroyed in alimentary canal cannot be given by oral route of administration
• It is not useful in pre-vomiting and patients of diarrhoea.
• Irritant or unpalatable drugs cannot be administered by oral route.
• Drugs with extensive first-pass metabolism cannot be administered by oral route.
• In oral route presence of food in GIT may interfere with absorption of drug.
• Oral administration of some drugs may disturb the micro-flora of GIT.
• Accurate blood levels of the drug cannot be maintained by oral route of administration.
18. SUB-LINGUAL ROUTE
In this route the preparation is kept below the tongue and allowed to dissolve in mouth cavity. The
active drug gets absorbed through the sublingual mucus membrane directly into blood circulation.
E.g. Nitroglycerin for acute anginal attack.
ADVANTAGES
• Rapid onset of action.
• Degradation of drug is avoided in stomach.
• Inactivation of drug in lever is avoided.
• Presence of food in GIT does not affect the absorption of the drugs.
DISADVANTAGES
• Not suitable for large doses and frequent use of drugs.
• Some drugs may cause irritation to buccal mucosa.
• Excessive salivation may cause swallowing of drug.
• Doses of drugs having direct or toxic effects should be administered carefully to avoid systemic
side effects.
19. RECTAL ROUTE
The route of administration in which the drug is in the form of solution and is introduced into the
rectum is called rectal route, e.g. enema preparation, suppository etc.
ADVANTAGES
• If oral and other routes of administration produces irritation, this route may be used.
• This route is highly recommended when local effects in rectum and bowl movement is required.
• When patients do not swallow the drug or children who do not co-operate in taking medicines, this
route may be opted.
DISADVANTAGES
• This route is generally not liked by the patient.
• A few drugs may produce local irritation of anal mucosa.
• The absorption of drug is not complete because less surface area is available for absorption as
compared to oral route.
20. PARENTERAL ROUTE
Routes of administration of drugs other than enternal route or routes other than operating through
alimentary canal are called parenteral routes.
In this case, the drug in the form of solution or suspension is injected in the body with the help of
hollow needle and syringe for either systemic or site specific effects.
ADVANTAGES
• Parenteral routes of administration have rapid onset of action.
• Drugs which are not palatable or irritate the GI tract can be given by this route.
• More accurate dose can be administered and more accurate blood level of drugs can be maintained as
compared to oral route of drug administration.
• This route is best in cases of vomiting and diarrhoea.
• This route is best and most useful in unconscious and uncooperative patients.
• The drugs which are destroyed in GIT can be given by this route.
• The smaller quantity of drugs are required by this route, also this route is useful in clinical
emergencies.
21. • Large quantities of drugs can also be administered by this route, e.g. saline solution.
• Maximum or 100% bioavailability is possible by IV route.
DISADVANTAGES
• This route is inconvenient to the patient and for frequent administration of drugs.
• Skilled person is necessary and always required for administration of drugs.
• Strict aseptic technique is to be followed during drug administration.
• There is a possibility of pain and edema at the site of application.
• Self administration of drugs from this route is very difficult.
• The sterilization of syringe and needle is necessary in this route of administration.
• There is a possibility of blood capillaries damage in this route of administration.
• Once the drug is absorbed in blood circulation, drug effects and adverse effects cannot be reversed or
controlled.
22. INTRAVENOUS ROUTE (IV ROUTE)
In this route the drug is directly injected into the lumen of vein. The drug produces rapid action and desired
blood concentration can be achieved by a definite dose of a drug.
ADVANTAGES
• The onset of action is very rapid.
• This route is effective in clinical emergencies.
• Large quantity of drugs can be administered by this route, e.g. normal saline solution.
• Drugs which produces irritation and pain by other routes can be given by IV route.
• Hypertonic solutions can be administered intravenously because the drug is diluted by the bloodstream.
• Desired and accurate blood concentration of drug can be achieved by this route.
• Only a minimum quantity of drug is required to get a particular drug effect as compared to other routes.
• Control on the rate of administration of drug is possible in this route.
• Complete or maximum bioavailability of a drug can be assured by IV route of drug administration.
23. DISADVANTAGES
• Self drug administration from this route is very difficult.
• Sometimes, leakage of drug outside the vein produces severe irritation and abscess formation.
• This route is inconvenient to the patient and for frequent administration of drugs.
• Skilled person is necessary and always required for administration of drugs.
• Strict aseptic technique is to be followed during drug administration.
• There is a possibility of pain and edema at the site of application.
• The sterilization of syringe and needle is necessary in this route of administration.
• Speed of the drug entering through this route needs constant supervision.
• Once the drug is absorbed in blood circulation, drug effects and adverse effects cannot be reversed or
controlled.
24. INTRAMUSCULAR ROUTE (IM ROUTE)
In this route the drug is directly administered into the dense muscular tissue.
ADVANTAGES
• Mild irritants, suspensions, colloids and injections with insoluble oily bases can be administered by this
route.
• Absorption of water soluble drugs is rapid in this route than oral and sub-cutaneous route.
• Massaging and application of the heat at the site of injection by IM route may increase the drug
absorption.
• The drugs administered by this route from tissue depots from where drug is slowly released and this
provides prolonged duration of action.
DISADVANTAGES
• Sterilization of syringe and needle is necessary in this route.
• Skilled person is required for drug administration in IM route of administration.
• Some drugs cause irritation and pain when administered by IM route.
• If proper care is not taken there are chances of injury to the nerves.
• Total volume of drug injected by IM route is restricted up to 10mL.
• Certain oil based IM injections require more time for absorption as compared to oral rotes.
25. SUBCUTANEOUS ROUTE
A subcutaneous injection is administered into the sub-cutis, the layer of skin directly below the dermis and
epidermis, collectively called as the cutis.
ADVANTAGES
• Drugs with low oral bioavailability can be administered and depot preparations can be inserted into the sub-
cutaneous tissue.
• Useful in patients whose vein identification is tedious.
DISADVANTAGES
• Slow absorption of drugs as compared to IV and IM route, hence not suitable for emergency.
• Difficult to administer to paediatrics and geriatrics and suitable only for non-irritant drugs.
INTERADERMAL ROUTE
In this route the drug is administered into the dermis, just below the epidermis layer of the skin.
ADVANTAGES
• Used for sensitivity and allergy testing’s.
• Vaccinations are generally administered by this route.
DISADVANTAGES
• A small quantity of drug can be administered.
• This route is generally painful.
26. INTRATHECAL ROUTE
Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so
that it reaches the cerebrospinal fluid (CSF).
ADVANTAGES
• It is useful in spinal anaesthesia, chemotherapy and in pain management applications.
• This route bypass the blood brain barrier for drugs with poor penetration into the CNS.
DISADVANTAGES
• Special skilled personnel are required to administer drugs from this route.
• Intrathecal administration requires a strict aseptic technique.
INHALATIONAL ROUTE
Volatile liquids and gases are given by inhalation for systemic effects, e.g. General anaesthetics.
ADVANTAGES
• Quick onset of action and dose required is very less.
• Amount of drug administered can be regulated.
DISADVANTAGES
• As the drug directly enters the heart , there are chances of cardiac toxicity.
• Local Irritation may occur and specially designed apparatus is essential for administration of drugs.
27. TRANSDERMAL ROUTE
The drug is administered in the form of patch on the skin wherein active ingredients are delivered across the skin for
systemic distribution, e.g. oestrogen patch for hormone replacement therapy or contraception.
ADVANTAGES
• Patient compliance is better.
• Duration of action is prolonged.
• Provides a constant plasma concentration of the drug.
• First pass metabolism is bypassed.
• Drugs can be delivered at a predetermined and controlled rate.
• Drugs with a lipophilic character, however, are better suited for transdermal delivery.
DISADVANTAGES
• This route of administration is generally expensive.
• Local irritation may cause dermatitis and itching.
• Patch may fall off unnoticed.
• Transdermal route of drug administration cannot achieve high drug levels in blood/plasma.
• The barrier function of the skin changes from one site to another on the same person, from person to person and
with age.
• Many drugs with a hydrophilic structure having a low penetration through the skin and have difficulty in
absorption through this route.
28. INTRA-ARTERIAL ROUTE
In this route, a drug is directly injected into the artery.
ADVANTAGES
• This route leads to localisation of the drug effect in a particular organ or tissue.
• This route can be used for diagnostic studies.
• Also used for the administration of anti-malignancy drugs.
DISADVANTAGES
• Drugs administered may produce a sudden high concentration of drug in the arterial blood and
hence may be harmful locally or fatal to the tissue.
• Physical damage to the artery may occur if procedure not executed correctly.
• Special expertize is needed to administer drugs from this route.
29. INTRA-ARTICULAR ROUTE
Intra-articular injection involves administration of certain drugs directly into a joint, e.g.
Hydrocortisone acetate is given by this route in the treatment of rheumatoid arthritis.
ADVANTAGES
• Site specific application along with localisation of the drug effect in a particular organ or tissue.
• Drugs can be administered to big joints such as knee joints.
DISADVANTAGES
• High sterility is required as deep tissue injection has to be given.
• Specialized skilled personnel and advanced techniques are required.
