General Pharmacology

Objectives
What is pharmacology?
What is a drug?
Medication Names
Pharmacological characteristic of drugs
Pharmacodynamics
Typical mechanisms of action of a medicine
Doses
Routes of Drugs Administration
Steps to Administering Medication

What is Pharmacology ?
Pharmacology is a branch of medical science
“Pharmakon” - Greek word means “an active principle”
“Logos” - Greek word means “knowledge”
So, Pharmacology is “knowledge about drugs” in common meaning

In broad aspect, it is the subject that embraces the knowledge of history, source, physical and chemical properties, compounding, biochemical and physiological effects, mechanism of action, absorption, distribution in the body, storage, biotransformation (or metabolism), excretion and therapeutic and other uses of drugs
Definition

What is a drug?
The word drug is derived from French word “Drogue” [meaning a dry herb]
A drug is defined as any substance used for the purpose of diagnosis, prevention, relief or cure of a disease in man or animal

Any substance or product that is used or intended to be used to modify or explore physiological system or pathological states for the benefit of the recipient
WHO Definition of drug

Sources of Drugs
Animals
Plants
Minerals
Synthetic
Microbes
Biotechnology

Medication Names
Chemical Name
- describes the drug’s chemical structure N-(3-dimethylaminopropile)-iminodibenzile hydrochloride
International non-patented name (INN), or Official Name –
the name used in the Pharmocopoeia
Imipramine (Imipraminum)

Medication Names
Trade Name
the name the manufacturer uses to market the drug
Мelipramine (Egis, Hungary)
Imizine (Russia)

What is General Pharmacology?
General Pharmacology is the study of the common patterns of drugs Pharmacodynamics and Pharmacokinetics

Pharmacological characteristic of drugs
Each drug has
Pharmacokinetics Pharmacodynamics
What body does to drug What drug does to body

Pharmacodynamics
(from Greek pharmakon – drug, dynamis - power)
Pharmacodynamics includes:
A) Biologic effects of the drug: both beneficial & harmful effects
What does a drug do in the body?
B) Localization of action
Where does a drug act in the body?
C) Mechanism of actions of the drug
How does a drug act in the body?

Pharmacodynamics:
effects of the drugs
Thrapeutic effects
The desired result of drug administration
Side effects
Effects that are not desired and that occur in therapeutic doses in addition to the desired therapeutic effects

Effects and side effects
Drug effects and side effects result from interaction with individual receptors
All drugs interact with more than one receptor
Endogenous molecules usually bind to multiple receptors in the same family
Drugs are designed to target specific receptor subtypes to reduce side effects
Increasing the concentration of the drug increases side effects
Patients experience different effects and side-effects

Drugs can do good as well as harms
Beneficial effects/Therapeutic effects
Harmful effects / Adverse effects
So, the knowledge of basic pharmacology is essential for all prescribing physicians and especially for pharmacists
Drugs do benefit as well as harm

“Poisons in small doses are the best medicines; and useful medicines in too large doses are poisonous”
William Withering, discoverer of Digitalis
Drugs do benefit as well as harms

FACTORS THAT AFFECT
Pharmacodynamics of MEDICINES
Exogenous factors unrelated to the patient: chemical structure and physical properties of drugs, medicinal form, route of administration and dose, diet, food composition, environment, chrono-dependence
Endogenous factors related to the patient: body weight, sex, age, physiological (pregnancy, hypodynamy, body temperature) and pathological (disease) conditions
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Typical mechanisms of action of a medicine
Basic "target" of action of a medicine is receptor
Receptors are active groups of substrates’ macromolecules, with them a drug interacts.
Receptors are the components of a cell membrane or cytosole that interact with a drug and initiate the chain of biochemical events leading to the drug’s observed effects
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Types of receptors
R
ions
R
R
R
G
G
E
E
R
nucleus
Cell membrane
mRNA synthesis
agonist
R - receptor
E - enzymes
G – G-proteins
Receptors directly controlling ion channel function. These are receptors
coupled directly with ion channels (nicotinic cholinoreceptors,
GABAA-receptors and glutamate receptors).
Receptors coupled with effector via ”G-protein – second messengers”
or ”G-protein – ion channel” systems (muscarinic cholinoceptors,
adrenoceptors).
Receptors directly controlling effector enzyme function. They are directly
associated with thyrosine kinase and regulate phosphorilation of proteins
(insulin receptors and a number of growth factors function this way).
Receptors controlling DNA transcription are intracellular receptors (soluble
cytosolic or nuclear proteins) unlike membrane receptors of types 1-3.
Steroid and thyroid hormones interact with this type of receptors.

1. Medicines - agonists (agonists - the contender): it is provided “affinity" (affinis - related) medicines.
2. Medicines - antagonists or blockers:
competitive, non-competitive.
3. Medicines - agonists-antagonists.
4. Medicines - modulators change structure of a receptor,
cooperating with its allosteric center.
Receptors, enzymes, ion channels (Na+, Са2+, К+, Сl- , etc.), transport systems and genes serve as “target" for drugs
Typical mechanisms of action of a medicine

Kinds of action of a medicine
For the analysis pharmacodynamic distinguish:
- Local and resorptive (or systemic) action;
- Direct and reflex action;
- Selective (predominant) and non-selective action;
- Principal and adverse effects;
Reversible (characteristic of most drugs) and irreversible action (in a case of covalent bond, as a rule).
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Pharmacotherapeutical kinds of action
Etiotropic
Pathogenetic
Symptomatic
Stimulative
Subsitutive
Palliative (time alleviation)

Negative kinds of drug action
Cumulation: material, functional.
Accustoming (tolerance), tachyphylaxis (rapidly diminishing response to successive doses of a drug, rendering it less effective. The effect is common with drugs acting on the nervous system).
Predilection; euphoria; abstinence.
Medicinal allergy.
Medicinal idiosyncrasy.
Dysbiosis (dysbacteriosis).
Embriotoxity → teratogenic → mutagen.
Blastomogenic (cancerogenic).
Withdrawal Syndrome
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Kinds of doses
Therapeutical:
-Minimal -Single -Isolethal
-Average -Daily -Isoeffective
-Maximal -Course -Equimolecular
Shock and supporting doses
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Dose is a quantity of a substance for intake.
Dose is usually measured in grams or gram fractions (mg and so on),
in special cases – in radioactivity units or in biological units
(in biostandardization).
For more accurate dosing of drugs their amount is calculated
per 1 kg of body mass (for example, mg/kg) or by body surface
area (per 1 m2).

Therapeutic index
Where
LD50 - the dose that causes death in 50% of experimental animals;
ED50 - the dose that causes pharmacological effect in 50% of animals.
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TI =
LD50
___________________________
ED50

“Dose-effect” dependence
Inactive doses
Therapeutic window
Toxic doses
Threshold
(Minimally active dose)
Minimal toxic dose
Lethal dose
Dose
Effect

This is an interval between minimal therapeutic dose (or concentration) and minimal toxic dose (concentration)
For safety use of drugs this interval has to be wide enough
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Therapeutic window or breadth of therapeutic action

In geriatrics - 1/2-2/3 from an average therapeutic dose
The children's dose (А) is calculated using the formulas:
B- a dose of an adult person;
а - age of a child;
В - weight of a child.
The important quality of a medicine is not the “strenth" of its action but the efficiency of a safe dose
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A =
a
_________________________________
B∙(a + 12)
A =
B
_________________________________
(70 kg)∙ B where

Routes of Administration of drugs
Enteral (via digestive tract):
Oral, sublingual, transbuccal*, duodenal and rесtal routs
* from Latin bucca – cheek
Parenteral: subcutaneous, intramuscular, intravenous, intra-arterial, intracardial, intrasternal, intraperitoneal, inhalation, subarachnoid, suboccipital and some others
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Oral (by mouth, internally, pеr os):
The most common administration rote
Positive: is a convenient and simple way,
gastrointestinal tract is the "biological filter",
medical personnel and equipment are not needed,
many drugs are used 30-40 minutes before eating or 3-4 hours after it
Disadvantages: the concentration of drugs is not exact,
drugs can be destroyed in the gastrointestinal tract by interaction with food enzymes and hydrochloric acid,
is not suitable for the first aid,
speed and completeness of absorption of drugs can vary,
inactivation in the liver and action on it are possible
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Oral route of administration of medicines
Introduced inside the mouth
Throgh the esophagus enters the stomach
Absorbed from the stomach to the liver through a capillary
From the liver medicine comes to the bottom nailed veins
Then to the right atrium and right ventricle
From the right ventricle to the pulmonary artery to lungs
Then to the left atrium and left ventricle
The left ventricle enters the aorta and then to organs and tissues
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Rectal administration
Positively: can be used in the unconscious, patients with vomiting, stomach diseases, in mentally ill, children.
Absorbtion speed is close to intramuscular way
(5-15 minutes). There is a "biological filtration” and no effect of the first passage through the liver.
Disadvantages: uncomfortable way,
not all drugs are absorbed.
Sublingual
Quick adsorbtion, drugs are not destroyed in the gastrointestinal tract and less - in the liver.
Only for potent drugs.
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Parenteral way
Positive: fast action and accurate dosing,
introduction to the unconscious is possible,
drugs are not destroyed in the gastrointestinal tract including the liver.
Disadvantages:
the need of the strict asepsis,
the participation of medical personnel and equipment is needed,
the risk of infection,
introduction is accompanied with pain.
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Intravenous way - usually under the net-applied conditions. unable to administer oil solutions, suspensions, solutions, causing hemolysis, thrombosis, conversion of hemoglobin to methgemoglobin; danger of platelet-phlebitis.
Subcutaneously - water and oil solutions are injected.
Intramuscularly – quick effect (10-15 minutes),
volume should not exced 5 ml.
Inhalation: fat-soluble injected drugs are well absorbed through the alveoli.
Subdural, epidural, transdermal, intracardiac, and others.
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Parenteral way

Characteristics of the main routes of parenteral injection of medicines
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Physicians and pharmacists should remember that the right choice of dose, route of introduction of drugs, application of preparations’ etiotropic, pathogenetic, symptomatic action - the important condition of pharmacotherapy of any disease.
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Steps to Medication Administration

Select Proper Medication
Avoid contamination
Check Expiration Date
Check For Signs of Contamination
Discoloration
Cloudiness
Particulate Matter
Steps to Medication Administration

Verify Form & Route
Inform Patient of Order
Inquire about allergies
Recheck Medication
Expiration date
Contamination
At least two more times after initial check
Steps to Medication Administration