Comprehensive Overview of Pharmacology and Drug Administration Routes

Pharmacology
Pharmakon: Meaning drug, medicine, or poison
Logia: Meaning the study of or knowledge of
Pharmacology is the science of drugs.
Oswald Schmiedeberg, regarded as the ‘father of pharmacology’

Drug (French: Drogue—a dry herb)
It is the single active chemical entity present in a medicine that is
used for diagnosis, prevention and treatment/ cure of a disease.
The WHO (1966) 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 ‘drug’ should refer to a substance that has
some therapeutic/diagnostic application.

Pharmacology is the scientific study of the effects of drugs and
chemicals on living organisms .
Include Study of
History , Properties
Physiological effects – pharmacological action and adverse effect
Mechanism of action
Absorption, distribution, metabolism, excretion
Uses of drug

Pharmacotherapeutics:
It is the application of pharmacological information together with
knowledge of the disease for its prevention, mitigation or cure.
Selection of the most appropriate drug, dosage and duration of
treatment taking into account the specific features of a patient are a
part of pharmacotherapeutics.

Clinical pharmacology
It is the scientific study of drugs (both old and new) in man.
It includes pharmacodynamic and pharmacokinetic investigation in healthy
volunteers and in patients.
Toxicology
It is the study of poisonous effect of drugs and other chemicals (household,
environmental pollutant, industrial, agricultural, homicidal) with emphasis on
detection, prevention and treatment of poisonings.
It also includes the study of adverse effects of drugs, since the same substance
can be a drug or a poison, depending on the dose

Chemotherapy
It is the treatment of infection/malignancy with specific drugs that
have selective toxicity for the infecting organism/ malignant cell with
no/minimal effects on the host cells.

DRUG NOMENCLATURE
Chemical name It describes the substance chemically, e.g. 1-(Isopropylamino)-3-(1-
naphthyloxy) propan-2-ol for propranolol
Proprietary (Brand) name It is the name assigned by the manufacturer(s) and is his
property or trade mark.
One drug may have multiple proprietary names, e.g. ALTOL, ATCARDIL, ATECOR, ATEN,
BETACARD, LONOL, TENOLOL, TENORMIN for atenolol from different manufacturers.

Non-proprietary name/generic name
It is the name accepted by a competent scientific body.
‘generic’ should be applied to the chemical or pharmacological group
(or genus) of the compound, e.g. phenothiazines, tricyclic
antidepressants, aminoglycoside antibiotics

Pharmacokinetics
(Greek: Kinesis—movement)
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 (ADME)
What the body does to the drug.

Paracetamol is rapidly and almost completely absorbed orally attaining peak
blood levels at 30–60 min; (A)
25% bound to plasma proteins, widely and almost uniformly distributed in the
body (volume of distribution ~ 1L/kg); (D)
extensively metabolized in the liver, primarily by glucuronide and sulfate
conjugation into inactive metabolites (M)
which are excreted in urine; has a plasma half life (t½) of 2–3 hours and a
clearance value of 5 ml/kg/min. (E)

Pharmacodynamics
(Greek: dynamic—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

Factors affecting choice of route of drug
administration
1. Physical and chemical properties of the drug (solid/ liquid/gas;
solubility, stability, pH, irritancy).
2. Site of desired action—localized and approachable or generalized
and not approachable.
3. Rate and extent of absorption of the drug from different routes.

5. Effect of digestive juices and first pass metabolism on the drug.
6. Rapidity with which the response is desired (routine treatment or
emergency).
7. Condition of the patient (unconscious, vomiting).
The route of drug administration is important because it affects
drug metabolism, drug clearance, and thus dosage.

ENTERAL ROUTE (ORAL INGESTION)
The large surface area of the gastrointestinal tract, the mixing of its contents and
the differences in pH at different parts of the gut facilitate effective absorption of
the drugs given orally.
The acid and enzymes secreted in the gut and the biochemical activity of the
bacterial flora of the gut can destroy some drugs before they are absorbed.

ADVANTAGES
1. Safest route
2. Most convenient
3. Most economical
4. Drugs can be self-administered
5. Non-invasive route.
Oral route/ Oral ingestion

DISADVANTAGES
1. Onset of action is slow
2. Irritant and unpalatable drugs cannot be administered.
3. Some drugs may be destroyed by gastric juices, e.g. insulin.
4. not Suitable for unconscious and uncooperative patients.
5. Some drugs may undergo extensive first pass metabolism
in the liver. Nitroglycerin and Propranolol.
Oral route/ Oral ingestion

Advantages
✅ Rapid onset of action (within 1–5
minutes)
✅ Bypasses first-pass metabolism in the
liver
✅ Avoids degradation by gastric acid and
digestive enzymes
✅ Higher bioavailability for many drugs
Disadvantages
❌ Suitable only for potent, lipid-soluble,
small doses drugs (60 mg)
❌ Eating, drinking, or smoking can reduce
absorption
❌ Unpleasant taste or irritation may
produce
❌ Not suitable for unconscious or
uncooperative patients

PARENTERAL ROUTE
para (outside) and enteron (intestine)

ADVANTAGES
Action is more rapid and predictable than oral administration.
These routes can be employed in an unconscious or uncooperative patient.
Gastric irritants can be given parenterally
It can be used in patients with vomiting or those unable to swallow.
Avoid first pass metabolism of drug

DISADVANTAGES
require Trained professional
Asepsis must be maintained
Injections may be painful
More expensive, less safe and inconvenient
Injury to nerves and other tissues may occur

Subcutaneous injection technique
Insulin, Human Chorionic Gonadotropin (Hcg)
MMR Vaccine,Varicella Vaccine(The chickenpox vaccine)
Heparin

SUBCUTANEOUS (SC) INJECTION
Subcutaneous (SC) injections are given into the fatty tissue layer just
beneath the skin
Here the drug is deposited in the SC tissue
 As this tissue is less vascular, absorption is slow and largely uniform
making the drug long-acting
It is reliable and patients can be trained for self-administration.

Advantages of subcutaneous route of drug administration
1. It is a good route of administration especially in skin infections.
2. It is relatively safer than intravenous and intramuscular routes
3. Absorption is slower thus; it is a good route if a prolonged effect is to be
achieved.
4. Self-administration is possible as the injection need not be penetrated deeply.

DISADVANTAGES
As SC tissue is richly supplied by nerves, irritant drugs can cause severe pain. Hence
such drugs cannot be injected. (suitable only for nonirritant drugs.)
Repeated injections at the same site can result in erratic absorption.
If the drug is irritating it might cause the sloughing off of the skin hence it is not
suitable for emergency.
Only small volumes can be administered. (2ml )

INTRADERMAL
It is a shallow or superficial injection of a substance into the dermis, raising a
bleb
0.1 mL quantity can be administered and it may be painful
Diagnostic Skin Tests: Tuberculin test for tuberculosis
Immunizations: rabies, influenza, Bacillus Calmette-Guérin (BCG) vaccine,
smallpox vaccine
Allergy Testing

INTRAMUSCULAR (IM)
Aqueous solution of the drug is injected into one of the large skeletal muscle
(deltoid, triceps, gluteus or rectus femoris.)
As the muscles are vascular, absorption is rapid and quite uniform.
The volume of injection should not exceed 10 mL.
COVID-19 shots, Influenza (Flu)) , Tdap, Hepatitis B
Ceftriaxone, Penicillin G ,Streptomycin
Epinephrine (for severe allergic reactions/anaphylaxis)

INTRAMUSCULAR ROUTE ADVANTAGES
Rapid Drug Absorption:
Richly vascularized muscle tissue allows medication to be absorbed quickly into the
bloodstream.
Bypasses the Digestive System:
Drugs destroyed by stomach acids.

Depot Injections for Sustained Release:
Certain medications can be formulated to deposit deep in the muscle,
allowing for a slow, continuous release of the drug over days, weeks, or
months (e.g., antipsychotics and certain contraceptives).
Administer larger Volumes and Viscous Drugs

DISADVANTAGES
Pain and Tissue Damage
Nerve Injury Risk:
Administering the injection incorrectly (especially in the gluteal region) risks
striking the sciatic nerve, which can lead to partial or permanent leg paralysis.
Erratic Absorption:
The rate at which the medication enters your bloodstream relies heavily on your
muscle bulk and local blood flow.
If muscle blood flow is poor (e.g., in shock, muscle atrophy, or older age), the
medicine may not absorb

Intravenous (i.v.)
The drug is injected as a bolus (Greek: bolos–lump) or infused slowly over hours in
one of the superficial veins.

Advantages:
1. Rapid Onset of Action
2. 100% Bioavailability
3. Continuous Infusion beneficial for drugs that require steady blood levels, such as
in chemotherapy or pain management.
4. Administration of Irritating Substances as they are rapidly diluted in the
bloodstream.
5. Suitable for Unconscious Patients

Disadvantages
1. Requires Skilled Personnel
2. Asepsis must be maintained
3. Injections may be painful
4. More expensive, less safe and inconvenient
5. Injury to nerves and other tissues may occur
6. Risk of Adverse Reactions
*Since the drug is delivered directly into the bloodstream, any adverse reactions
to the medication can occur more rapidly and may be more severe compared to
other routes.

Uses
Targeted Cancer Therapy: Intended to provide high concentrations of drug
at a specific site, e.g. tumor
Imaging:
To Administer contrast agents to get high-resolution pictures of blood
vessels.(angiography)
Emergency condition:
Procedures like thrombolysis to rapidly dissolve blood clots.
Intra-arterial injection (IA)

• An intraperitoneal (IP) injection delivers medication or fluids directly
into the peritoneal cavity (the space holding abdominal organs like
the stomach and intestines).
• In humans, it is primarily utilized to administer regional
chemotherapy for ovarian cancer and for peritoneal dialysis.
• It is also the standard administration route in preclinical animal
studies.

An intrathecal injection
Involve injecting medication into the
cerebrospinal fluid (CSF) surrounding
the spinal cord
Useful several applications
For Spinal Anesthesia
Chemotherapy
Pain Management

the intramedullary/intraosseous (IO) route
drugs are mainly given when rapid vascular access is needed and IV access is
difficult , especially in emergencies.
Common drugs administered by intramedullary/intraosseous (IO) route
Adrenaline Cardiac arrest
Atropine Symptomatic bradycardia
Lidocaine Ventricular arrhythmias

“The right route ensures the right drug reaches the right
site at the right time.”
Thank You

Comprehensive Overview of Pharmacology and Drug Administration Routes

Comprehensive Overview of Pharmacology and Drug Administration Routes

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Comprehensive Overview of Pharmacology and Drug Administration Routes