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ANTIBIOTICS
SANJIB KUMAR YADAV
M.PHARM(PHARMACOLOGY)
LECTURER, DEPARTMENT OF PHARMACY,
CHHINNAMASTA EDUCATIONAL ACADEMY,
RAJBIRAJ, NEPAL
Yadavsanjibkumar@gmail.com

INTRODUCTION
 Antibiotics (Greek anti, “against”; bios, “life”) are chemical
compounds used to kill or inhibit the growth of infectious
organisms. Originally the term antibiotic referred only to
organic compounds, produced by bacteria or molds, that are
toxic to other microorganisms.
 They are more toxic to an invading organism than they are to
an animal or human host.
 first antibiotic was penicillin, discovered accidentally from a
mold culture.
 Antibiotics only treat bacterial infections. Antibiotics are
useless against viral infections (for example, the common
cold) and fungal infections (such as ringworm).

IDEAL PROPERTIES OF ANTIBIOTICS
1. kill or inhibit the growth of pathogens.
2. cause no damage to the host.
3. cause no allergic reaction to the host.
4. stable when stored in solid or liquid form.
5. remain in specific tissues in the body long
enough to be effective.
6. kill the pathogens before they mutate and
become resistant to it.

CLASSIFICATION OF ANTIBIOTICS
Antibiotics can be classified in many ways:
 Based on chemical structure.
1. Sulphonamides and related drugs.
- suphadiazine
- dapson
- para aminosalicylic acid
2. Diaminopyrimidines
- trimethoprime
- pyrimethamine

3. Quinolones
- nalidixic acid
- norfloxacin
- ciprofloxacin
4. Beta- lactum antibiotics
- penicillin
- cephalosporin
5. Tetracyclines
- tetracycline
- oxytetracycline
- doxycycline

6. Nitrobenzene derivative
- chloramphenicol
7. aminoglycosides
- streptomycin
- gentamicin
- amikacin
- neomycin
8. macrolides
- erythromycin
- clarithromycin
- azithromycin

9. polypeptides
- polymyxin-B
- bacitracin
- colistin
10. nitrofuran derivatives
- nitrofurantoin
- furazolidone
11. nitroimidazoles
- metronidazole
- tinidazole

12. nicotinic acid derivatives
- isoniazide
- pyrazinamide
13. azole derivatives
- miconazole
- clotrimazole
- ketoconazole
- fluconazole
14. polyene antibiotics
- nystatine
- amphotericin-B

 Based on spectrum of activity
1. broad spectrum antibiotics
- tetracyclines
- chloramphenicol
2. relative spectrum antibiotics
- cephalosporin
- rifamycin
3. narrow spectrum antibiotics
a. for gram + ve micro organism
- penicillin
- erythromycin

b. for gram – ve micro organism
- streptomycin
- gentamicin
c. anticancer antibiotics
- doxorubicin
- daunorubicin
d. antifungal antibiotics
- nystatin
- amphotericin-B
- griseofulvin

e. antiprotozoal antibiotics
- metronidazole
- tinidazole
f. antihelmintic
- mebendazole
- albendazole
g. anti viral antibiotics
- acyclovir
- zidovudin

 based on type of action
1. bacteriostatic
- sulphonamides
- tetracyclines
- chloramphenicol
- erythromycin
- ethambutol
2. bacteriocidal
- penicillins
- aminoglycosides
- cephalosporins

 based on mechanism of action
1. inhibit cell wall synthesis
- penicillins
- cephalosporis
- cycloserine
2. inhibit protein synthesis
- tetracyclines
- chloramphenicol
- aminoglycosides
- macrolids

3. cause leakage from cell membrane
- nystatin
- amphotericin-B
- polymyxins
- bacitracin
4. inhibit DNA gyrase enzyme
- ciprofloxacin
- norfloxacin
5. interfere with DNA function
- metronidazole
- rifampicin

6. interfere with DNA synthesis
- acyclovir
- zidovudin
7. interfere with metabolism
- sulphonamides
- sulfones
- trimethoprim
- PAS
- ethambutol

 based on obtained from
1. from fungi
- penicillins
- cephalosporins
- griseofulvin
2. from bacteria
- polymyxin-B
- bacitracin
3. from actinomycetes
- tetracycline - macrolides
- aminoglycosides, - chloramphenicol

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