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Renin Angiotensin Mechanism.

General Pharmacology - 1 (Introduction).


What is Pharmacology?

Pharmacology is the branch of pharmacy that deals with the study of drugs with main respect to their absorption, distribution, metabolism, excretion and its mechanism of action with therapeutic effects.

The word Pharmacology is derived from two words as follows
Pharmakon: Drug,
Logos: Study of,
Hence Pharmacology mans "Study of Drugs."


What is a Drug:

The drug can be defined as any substance used for diagnosis, prevention, mitigation, treatment or cure of disease or ailment.

e.g. Paracetamol (Crocin)

Drugs can be obtained from many sources like,

Sources of drugs:
Source

Examples

Plant
Morpine from Opium, Hyoscyamine from Datura, Digitoxin from Digitalis.
Animal
Insulin, Heparin, Thyroid extract etc.
Mineral
Liquid paraffin, Aluminium hydroxide, Lithium bromide etc.
Synthetic
Paracetamol, Aspirin, Nimesulide etc.
Microorganism
Penicillins, Cephalosporins etc.
Semi-synthetic
Amoxicillin, Homatropine etc.

These drugs vary in their chemical nature like,
Chemical nature
Examples  
Alkaloids
Morphine, Atropine, Emetine etc …
Glycosides

Digitalitoxin,  Amygdalin etc
Fixed Oils

Castor oil, Shark Liver oil etc.

Volatile Oils

Peppermint oil, Eucalyptus oil etc

Gums

Agar, Tragacanth, Acacia etc

Tannins

Black catechu, Pale catechu etc

Minerals

Liquid paraffin, Calamine etc

Hormones
Insulin, Testosterone etc

Resin

Balsam of Tolu, Balsm of Peru.

What are Pharmacokinetics and Pharmacodynamics?
Pharmacokinetics:
  • The study of the movement of drug molecules through a body is called as Pharmacokinetics. 
  • It deals with the study of ADME (Absorption, Distribution, Metabolism, Excretion) of drug and their relation to therapeutic response.
  • Simply it is called as the fate of drug or study of "What body does to the drug).
  • e.g.: Pharmacokinetics of Aspirin (Disprin)
Absorption; Aspirin being acidic in nature shows good absorption from the acidic environment of the stomach.
Distribution: It shows good plasma protein binding (80%) and gets distributed to most tissues.
Metabolism: Aspirin gets metabolized in the liver by conjugation reaction.
Excretion: Mainly through kidney via urine.


Pharmacodynamics.
  • The study of interaction of drug with living systems with reference to therapeutic response is called as Pharmacodynamics.
  • It deals with study of mechanism of actions and therapeutic responses of drugs.
  • Simply it is study of (what drug does to Body).
  • e.g. Pharmacodynamics of Salbutanol (Asthaline)
Therapeutic response: Bronchodilation.
Indication: Bronchial asthma.
Mechanism of Action: Salbutamol binds and stimulates adrenergic B2 receptors present in lungs and produces bronchodialtion.

What is a Dosing Regimen?

It can be defined as a frequency in which a specific dose of drug is administered for a set of time.



What is a Dose?

It is the minimum amount of drug required to be administered to produce desired therapeutic response.

e.g Aspirin 5mg (Colsprin,ASA): Dose = 5 mg, therapeutic response = Anti-platelet.


What is Clinical Pharmacokinetics?

Clinical Pharmacokinetics is the branch of pharmacy that deals with study pharmacokinetic principles to optimize therapeutic response of the drug in order to cater individual patient needs by improving dosing regimen.



What is Pharmacotherapeutics?

It is the application of drug in treatment or management of disease.

e.g. Aspirin is given to reduce pain and fever.


What is Chemotherapy?
  • The use of chemicals to kill or suppress the microbes ( Bacteria, Fungi, Viruses, Protozoa etc) in treatment of infectious diseases is called as Chemotherapy.
  • The drugs or chemicals used in therapeutics are called as chemotherapeutic agents.
  • The chemotherapeutic agents are smart drugs that can produce larger impact on parasite's cells with less or no harm to host cells.
  • As cancer cells are just like parasites to the body the anti-cancer drugs are also refereed as chemotherapeutic drugs.

e.g.

Penicillin in treatment of Syphilis.
Chloroquin in treatment of Malaria.
Isoiazide in treatment of Tuberculosis.
Acyclovir in viral infections.
Cyclophosphamide in treatment of Cancer.
Flucoazole in Fungal Infections.


What is Toxicoloy?
  • Toxicology is defined as branch of pharmacy that deals with study of adverse effects of drugs, causes, symptoms and treatment of poisoning.
  • Simply it is called as science of poisons.
  • e.g. Atropine Poisoning.
Cause; Accidental ingestion, Sucidal intention, Clinical overdose.
Symptom; Dryness of mouse, fever, tremors.
Antidote; Physostigmine.


What is Bioavilability?

Amount of drug from given dose that reaches systemic circulation intact is called as bioavialability.

Note that drugs given by I/V route produces practically 100% bioavialability.
Based on rutes of administration the bioavailability status is                                                            I.V. > I.M.> S.C.> ORAL > TOPICAL

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