2. Nature And Sources Of Drugs
DRUG
DRUG:
A chemical substance, especially one prescribed by a medical provider, that is
used in the diagnosis, treatment, or prevention of a condition or disease.
Depending on the perpose drug can be categorized as-
curative drugs
suppressive Drugs
prophylactic drugs
curative drugs: these drugs cure or eliminate the diseased or infected
conditions.
suppressive Drugs: These drugs do not cure disease or infection, however,
only control and suppress the disease or infection.
prophylactic drugs: These drugs are involved in the prevention of disease
from occurring
3. Nature of drugs:
It is only logical that these drugs might arise from several sources. The sources of drugs have travelled through a complete
arc, being derived mainly from natural sources in the early centuries to being synthetically manufactured today. There is
also a grey area in between, which constitutes the semi-synthetic sources. While natural alkaloids and glycosides are still
used today, the synthetically manufactured drugs generally have higher yields that are significantly associated with
quality, purity and low cost.
the nature of drugs relates to the-
physical properties of drugs:
1. Physical state of drug
2. Drug size
3. Drug shape
4. Drug reactivity and drug-receptor bonds.
chemical properties of drugs: or on the basis of drug source
1.Alkaloids
2.Glycosides
3.Oils
4.Gums
5.Resins
4. SOURCES OF DRUGS
The sources of drugs could be natural or synthetic ,
NATURALSOURCES:
1.PLANTS
Atropine : Atropine is a medication used to treat certain types of nerve agent and pesticide poisonings as well
as some types of slow heart rate, and to decrease saliva production during surgery.It is typically
given intravenously or by injection into a muscle.
Morphine: Morphine is a pain medication of the opiate family that is found naturally in a dark brown, resinous
form from poppy plant.
Quinine:Quinine is a quinidine alkaloid isolated from the bark of the cinchona tree.
Digoxine, Digoxin is used to treat heart failure, usually along with other medications.It is also used to treat
certain types of irregular heartbeat.
5. 2.ANIMALS
Insulin :
Insulin is a hormone that is produced naturally in our bodies. Its main role is to
allow cells through out the body to uptake glucose (sugar) and convert it into a
form that can be used by these cells for energy.
Heparin :
Heparin is an anticoagulant (blood thinner) that prevents the formation of blood
clots. Heparin is used to treat and prevent blood clots caused by certain medical
conditions or medical procedures. It is also used before surgery to reduce the
risk of blood clots
A
ntitoxic sera:
The most common use of antiserum in humans is as antitoxin or antivenom to
treat envenomation.
6. 3.MINERALS
Magnesium sulphate:
Magnesium is a naturally occurring mineral that is important for many systems in
the body especially the muscles and nerves. Magnesium sulfate also increases
water in the intestines. Magnesium sulfate is used as a laxative to relieve
occasional constipation.
Iron :
Iron is a mineral that is naturally present in many foods, added to some food
products, and available as a dietary supplement.
Calcium:
Calcium is a mineral found in many foods. The body needs calcium to maintain
strong bones and to carry out many important functions
.
7. 4.MICROORGANISMS
Antibacterial agents are obtained from some bacteria and fungi.
Pencillins:
Penicillins are a type of antibiotic derived from Penicillium fungi. An antibiotic is a type
of medicine that inhibits the growth of, or kills, bacteria.
Cephalosporins:
Cephalosporins are a large group of antibiotics derived from the mold Acremonium
(previously called Cephalosporium). Cephalosporins are bactericidal (kill bacteria) and
work in a similar way to penicillins.
Tetracycline:
Tetracycline is used to treat infections caused by bacteria including pneumonia and
other respiratory tract infections; ; certain infections of skin, eye, intestinal, genital and
urinary systems; and certain other infections that are spread by ticks, lice, mites, and
infected animals. It is also used along with other medications to treat acne.
8. SOURCES OF DRUGS
5.HUMAN:
Some drugs are obtained from man ,e.g
Immunoglobulin from blood,
growth hormone from anterior pituitary and
chorionic gonadotrophins from the urine of pregnant woman.
SYNTHETIC :
Most drugs are now synthesized .e.g quinolones, omeprazole, sulfonamides,
pancuronium, neostigmine.
Many drugs are obtained from cell culture ,e.g urokinase from cultured kidney cells.
some are now produced by recombinant DNAtechnology ,e.g human insulin, tissue
plasmogen activator and some drugs byHybridoma technique, e.g monoclonal
antibodies.
9. 1.SYNTHETIC
• Presently majority of drugs are obtained synthetically
• Some of drugs which are earlier obtained from plant today synthesized in lab. Advantage
• Quality can be controlled
• Process is easier and cheaper
• More potent and safer
• Large scale production.,
Semi Synthetic
• These are mainly obtained by changing the chemical structure of natural obtaining drugs.
• Ex: Atropine bromide
• Penicillin substrates.( by changing –R side chain)
Human Source
• HCG Pregnant women
• Menotrophin Post Menopausal women urine
• Regular insulin Human
• Urokinase Human kidney cells
10. ROUTES OF DRUG ADMINISTRATION
Drugs may be administered by various routes .the choice of the route in a given
patient depends on the properties of the drug and the patients requirements.
A knowledge of advantage and disadvantage of the routes of drug administration is
essential.
The route can be broadly divided into:
Enteral
Parenteral
Local
11. ENTERAL ROUTE (ORAL INGESTION )
This is the most common ,oldest and safest routes of drug administration.the
large surface area of the GI ,the mixing of its content and the differences in pH at
different parts of the gut help effective absorption of the drugs given orally.
ADVANTAGES:
1.Safest route
2.Most convenient
3.Most economical
4.Drugs can be self-administered
12. DISADVANTAGES
1.Onset of action is slower as absorption needs time.
2.Irritant and unpalatable drugs cannot be administered.
3.Some drugs may not be absorbed due to certain physicalcharacteristics, e.g
streptomycin.
4.There may be irregularities in absorption.
5.Irritation to the GIT may lead to vomitting .
6.Some drugs may be destroyed by gastric juices.e.g insulin.
7.Cannot be given to unconscious and uncooperative patients.
8.Patients may forget to take the tablet which is the practicalproblem.
13. PARENTERAL ROUTE
Routes of administration other than the enteral route areknown as parenteral routes.Here the drugs are
directly delivered into tissue fluids or blood.
ADVANTAGES :
Action is more rapid and predictable than oral administration.
These routes can be employed in unconscious or uncooperative patients.
Gastric irritant can be given parenterally and therefore irritation to the GIT can be
avoided.
It can be used in patients with vomitting or those unable to swallow.
In emergencies parenteral routes are very useful.
Digestion by the gastric and intestinal juices and the firstpass metabolism are avoided.
14. DISADVANTAGES :
Injection may be painful.
More expensive less safe and incovenient.
Injury to nerve and other tissues may occur.
15. •INJECTION
•Intradermal
•The drug is injected into the layers of the skin by:
1. BCG vaccine ,tests for allergy.
2.By multiple punctures of the epidermis through a drop of the drug, e.g. Smallpox vaccine.
3.Only a small quantity can be administered by this route and it may be painful.
Subcutaneous (SC) injection
Here the drug is deposited in the SC tissue ,e.g.insulin,heparin.As this tissue is less vascular,
absorption is slow and largely uniform and this make the drug long-acting.
16. INTRAMUSCULAR:
Aqueous solution of the drug is injected into one of thelarge skeletal muscle –deltoid, triceps, gluteus or rectusfemoris .
Absorption into the plasma occurs by simple diffusion . Large molecules enter through the lymphatic channels .As the
muscle are vascular ,absorption is rapid .
ADVANTAGES :
• Intramuscular route is reliable.
• Absorption is rapid.
DISADVANTAGES :
• IM injection may be painful.
• Risk of nerve injury –irritant solutions can damage the nerve if injected near the nerve.The needle may also b
puncture the blood vessel.
17. INTRAVENOUS (IV)
Here ,the drug is injected into one of the superficial veins so that it directly
reaches the circulation and is immediately available for action.
Intravenous route show rapid effect and maintain level of drug in circulation.
• ADVANTAGES :
• IV route is useful in emergencies because the drug isimmediately available for action.It gives 100%
bioavailability.
• Large volume and irritants can be given,they quickly diluted inblood.
• No first pass
• Prevent gastric manipulation,Emergency situations.
DISADVANTAGES :
• Once injected ,the drug cannot be withdrawn.
• Irritation of the vein.
• Self medication is difficult.
• The solution should be sterile and strict aseptic measures shouldbe taken.
• Costly
• painfull
18. Intraperitonial :
Peritonium offers a large surface area for absorption .
Intra-articular:
Drugs are injected directly into a joint for the treatment ofarthritis and other
diseases of the joints.strict aseptic precautions are required,e.g .hydrocortisone is
injected into the affected joint,in rheumatoid arthritis
Intra-arterial:
Here the drug is injected directly into the arteries.it isused only in the treatment of
peripheral vascular disease, local malignancies and angiograms.
19. Inhalation :
Volatile liquids and gases are given by inhalation,e.g The drug particles and the fine droplets are inhaled as
aerosol,
e.g . Salbutamol.Inhaled drugs and vapour may act and absorbed on the pulmonary epithlium and mucous
membranes of the respiratory tract.
ADVANTAGES:
Almost instaneous absorption of the drug is achieved becauselarge surface area of the lungs.
Hepatic first pass metabolim is avoided.
Absorption and excretion through lunges.
