Pharmacology Pharmacology

Dr.Bikesh Pandey

PharmacologyPharmacology

• Literally :– Pharmakon = Drugs– Logos = Studies

• A science studying the principles of the interaction between drugs and organic body

PharmacologyPharmacology

• It deals with the:– Chemical and physical properties, – Action, – Mechanism of action,– Biotransformation, – Clinical uses, – Side effects, – Contraindications ………. of drugs.

DrugDrug• Derived from a French word ‘Drogue’ meaning dry her

b.

• There is no single, precise definition.

• A substance which has medicinal, intoxicating, performance enhancing effect when put into a human body.

Most commonly used psychoactive drugCOFFEE

Worlds most selling drug Cigarette

Greek God of medicine

- Asclepius

Rod of Asclepius

Drug

is a double edged sword !

ToxicologyToxicology

• Branch of pharmacology which deals with the undesirable effects of chemicals on living systems, from individual cells to ecosystem.

Cannabis

(Marajuana)

Important for painManagement but has

Been commonlyabused

Heroin (diacetylmorphine)

Another commonly abused drug

ParacelsusParacelsus : : Pioneer of toxicologyPioneer of toxicology

• "Alle Dinge sind Gift und nichts ist ohne Gift; allein die Dosis macht, dass ein Ding kein Gift ist."

• "All things are poison and nothing is without poison; only the dose makes a thing not a poison."

Drug nomenclature Drug nomenclature Normally  drugs  have  three  names:   1. Chemical :- describes the chemistry of the drug.   2. Non-proprietary – Generic

3. Proprietary - Trade or Brand name :- name assigned by the manufacturer and is his property or trade mark. For Atenolol eg. Altol, Aten, lonol.

– Brand names generally differ in different countries.

– Brand names are designed to be catchy, short, easy to remember and often suggestive,

– eg. LOPRESOR

For lowering BP

Example of drug nomenclature :Example of drug nomenclature :

Chemical name: 7 Chloro 1, 3 dihydro 1 methyl 5 phenyl – 2H – 1,

4 benzodiazepine – 2 – one.

Generic name: Diazepam Proprietary Name: Apozepam

Sources of drugsSources of drugs

According to sources they are:-

1.1.Natural drugsNatural drugsA. PlantsE.g. Digoxin from Digitalis purpurea

Atropine from Atropa belladonna Quinine from Cinchona officinalis

B. AnimalsE.g.. Insulin from pig Cod liver oil from Cod fish liver

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C. Minerals

E.g.. Iron, Iodine, Potassium salts.

D. Micro – organisms

E.g. Penicillin from penicillium notatum.

Chloramphenicol from Streptomyces

venezuelae (Actinomycetes).

2. 2. Synthetic drugsSynthetic drugs

- Prepared by chemical synthesis in pharmaceutical

laboratories

E.g.. Sulphonamides, quinolones,

barbiturates

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3. Semisynthetic drugs

- Prepared by chemical modification of natural drugs.

E.g.. Ampicillin from penicillin G.

Dihydroergotamine from ergotamine.

4. Biosynthetic drugs

- Prepared by cloning of human DNA in to the bacteria

like E.coli.

E.g.. Human insulin

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Route of Administeration of drugsRoute of Administeration of drugs• Orally [PO] - as a liquid or solid, that is taken orally & absorbed through the intestines.

• Inhaled - as an aerosol or dry powder.

• Injected – – Intramuscular [IM]– Intravenous [IV]– Intraperitoneal [IP]– Intraosseous [IO]– Subcutaneous [SubQ, SQ, SC, Subcut]

• Insufflation - snorted into the nose.

• Rectally [PR] - as a suppository, that is absorbed by the rectum or colon.

• Sublingually [SL] -diffusing into the blood through tissues under the tongue.

• Topically - usually as a cream or ointment.

• Vaginally [PV] - as a suppository, primarily to treat vaginal infections.

• Bolus is the administration of a drug to raise its concentration in blood to an effective level.

Tab. Tablet

Amp. Ampule

Cap. Capsule

Susp. Suspension

Syr. Syrup

Gtt(s) Drop(s)

OD Once daily

QD Once daily

BD / BID

Twice daily

TDS Three times a day

QID Four times a day

SOS As required

PRN As required

HS Before bedtime

a.c.  Before meals

Stat Immediately

tbsp. Tablespoon(15 ml)

tsp. teaspoon (5 ml)

SR Sustained release

IU International units

q._ _ = every _ _

• Eg:

» q6h

» q4h

» q24h

» q2min

» q30s

» q72h

General effects of drugsGeneral effects of drugs

Excitation

or

Inhibition

Excitation or stimulationExcitation or stimulation

Certain functions of the body can be enhanced by drugs.

Adrenaline increases heart rate and BP. Caffeine stimulates mental activities.

InhibitionInhibition

Propranolol decreases heart rate and BP.

Certain functions of the body can be inhibited by drugs.

Appropriate doses are important !!!

Over excitation hyperactivity

Over inhibition paralyze

Function failure

Clinical effect of drug actionClinical effect of drug action

• Therapeutic action

• Adverse reaction

Therapeutic actionTherapeutic action

• The desired effects for drug therapy.

• It is not the synonym of drug effect.

• Include etiological treatment and treatment of symptoms.

Treatment of symptoms for acute cases while etiological treatment for chronic

cases

A patient was having pneumonia with streptococci infection. He had a pain in his chest, high fever and a bad headache. He was very sick.

The doctor wrote a prescription to him.

Penicillin G Aspirin

Example

Rx:

1. Inj: Penicillin G 800,000U× im X bid X 7d

2. Tab: Aspirin 0.3g ×PO X TDS X 6d

Penicillin G is an antibiotic drug.

Aspirin has analgesic and antipyretic properties.

He may be treated by penicillin to combat the streptococci as etiological treatment, by aspirin to lower the fever as symptomatic treatment.

Adverse reactionAdverse reaction

The discomfort or painful reactions of the patients to the drug ,

which were not the purpose of drug therapy.

It includes :It includes :

• Side reaction

• Toxic reaction

• Residual reaction

• Withdrawal reaction

• Allergic reaction

• Dependence

Adverse reaction

Side ReactionSide Reaction

• Reaction not complying with the purpose of

drug therapy under the therapeutic dose.

• Related to low selectivity of drug.

Aspirin - an antipyretic analgesic and antiinflammatory drug

Clinical uses: Fever, Headache, toothache , menstrual pain, rheumatic fever, rheumatoid arthritis Small daily dose of aspirin for prophylaxis of stroke and cardiac infarction.

Example

But at the same time, aspirin may also cause gastric distress, nausea, vomiting, gastric ulcer and bleeding etc within therapeutic dose.

Toxic ReactionToxic Reaction

• Hazardous reaction due to overdose or over-accumulation

• Includes :– Acute toxicity

– Chronic toxicity

– Special toxic reaction• Carcinogenic • Teratogenic • Mutagenic

Acute toxicityAcute toxicity is a term referring to the administration of overdose of the drug.

Example: Used over dosage of barbiturates.

Barbiturate is one of the sedative-Hypnotics.

It depresses CNS at all levels in a dose-dependent fashion. Acute over dosage of barbiturate can lead to coma, diminished reflexes, severe respiratory depression, cardiovascular collapse death.

Chronic toxicityChronic toxicity is generated gradually by the accumulated drug in the body after long term administration.

Example: Long term usage of tetracyclines.

Tetracycline is one of the broad-spectrum antibiotics.

Long term usage or high dose tetracycline can produce hepatic dysfunction.

Residual ReactionResidual Reaction

• Effects of Remaining drugs under the threshold concentration after discontinuation of the drug

Example:

Hypoadrenocorticism after discontinuation of long-term use of glucocorticoid

Withdrawal ReactionWithdrawal Reaction

• AKA “Rebound effect”

• The original disease exacerbates after abrupt discontinuation of the drug.

Example:

Withdrawal steroid therapy suddenly results in adrenal suppression .

To Prevent such situation : the dose of original drug needs to be reduced gradually or administrate with alternative drugs.

Allergic ReactionAllergic Reaction

• Also called “Hypersensitive reaction”

• Commonly seen in allergic subjects, immune response to a non-peptide drug which acts as a semi-antigen

• It’s characteristic is not related to original drug effect

• It is independent of the dose.

Penicillin G can induce the allergic reactions in some patients, including typical anaphylactic shock.

Example of Example of Allergic ReactionAllergic Reaction

DependenceDependence

AddictionAddiction : Physical or Physiological dependence

HabituationHabituation : Psychic or Psychological dependence

Eg : Morphine

Physical adaptation is induced following repeated administration of some drugs.

Abstinence syndrome is reduced after discontinue.

Addiction

HabituationHabituation

Psychic desire and pleased feeling are induced following repeat.

Clinical effect of drug actionClinical effect of drug action

• Therapeutic action

• Adverse reaction•Side reaction

• Toxic reaction

• Residual reaction

• Withdrawal reaction

• Allergic reaction

• Dependence

ComplianceCompliance

• Degree of , “patient following doctors advice”

• When the patient is following the doctor’s advice strictly , then the compliance is very good;

• When the doctor’s advice is not followed properly, then the compliance is poor.

Empirical drugsEmpirical drugs

• Drug that is used only on the basis of experience , without any scientific pharmacological basis.

Empirical therapyEmpirical therapy

• When a treatment module is focused on broad spectrum rather than an exact etiology.

• E.g Broad spectrum being prescribed as antibiotic without confirming the etiological diagnosis.

Prescription writingPrescription writing Dr. ……… MBBS (TMU), china Registration number: - 2347

Date : ……………Name : ----------Age : ……… Sex : ………Address : …….. Weight : …….Occupation :…….. Religion : ……

• Chief complain (C/C) 1. Burning sensation in upper abdomen 2. Nausea • Diagnosis : GERD

• Rx. : - 1. Omeprazole 20mg two times a day for 7 days before meal Cap. Omeprazole - 20 mg X q12h X 7d

Doctor’s signature:------------

Two Main Areas In Pharmacology Two Main Areas In Pharmacology

Pharmacodynamics

Pharmacokinetics

Scope of pharmacology ?

PharmacodynamicsPharmacodynamics

Study of the biochemical and physiological effects of drugs and the mechanisms of drug action and the relationship between drug concentration and effect.

PharmacokineticsPharmacokinetics

Pharmacokinetics is a branch of pharmacology dedicated to the determination of the fate of substances administered externally to a living organism.

PharmacokineticsPharmacokinetics

PharmacodynamicsPharmacodynamics

Pharmacodynamic is the study of :“What a drug does to the body”

Pharmacokinetics is the study of :“What the body does to a drug”

Pharmacokinetics

What the body does to the drug

(movement of the drug)AbsorptionDistributionBiotransformationExcretion

Pharmacodynamics

What the drug does to the body

Mechanism of action

Pharmacological

actions

Adverse effects

Drug interactions

To be continued……..To be continued……..

PharmacokineticsPharmacokinetics

Drug at site of administration

Drug in plasmaDrug / metabolites in tissues

Drug / metabolites in

urine, feces, bile

AbsorptionDistribution

Elimination

Metabolism

Kidney

Liver

Pharmacokinetics Pharmacokinetics

Pharmacokinetics Pharmacokinetics Knowledge of pharmacokinetics helps the

doctor to determine:

How much drug is present in the body at any given time?

How long does it take to reach a constant level of drug in the body during chronic drug administration?

How long does it take for the body to get rid of drug once intake of drug has stopped?

The - EndThe - End