1. Antibiotics

2. General consideration
Chemotherapy: treatment of systemic infection with specific drug that selectively suppress the infecting microorganisms without significantly affecting the host.
Antibiotics: these are the substances produced by microorganisms which suppress the growth or kill the microorganism at very low concentration.

3. Classification of antibiotics
On the basis of chemical structure
Circonamide and related drugs – Sulphadiazine, Sulphone (Dapsone, Paraaminosalicylic acid)
Diaminopyrimidine – Trimethoprim, Pyrimethamine
Quinolones – Norfloxacin, Nalidixic acid, Ciprofloxacin
Beta lactum antibiotics – Penicillins, Cephalosporins, Monobactam, Carbapenems
Tetracyclines – Oxytetracycline, Doxycycline
Nitrobenzene derivatives – Chloramphenicol
Aminoglycosides – Streptomycin, Gentamicin, Neomycin

4. Classification of antibiotics
h Macrolides antibiotics – Erythromycin, Roxithromycin, Azithromycin
Polypeptide antibiotics – Polymyxin-B, Colistin, Bacitracin
Glycopeptides – Vancomycin, Teicoplanin
Oxyzolidinone – Linezolid
Nitrofurantoin derivatives – Nitrofurantoin, Furazolidone
Nitroimidazole derivative – Metronidazole, Tinidazole
Nicotinic acid derivatives – Isoniazide, Pyrazinamide, Ethionamide
Polyene derivatives – Nystatin, Amphotericin-B, Hamycin
Azole derivatives - Ketoconazole, Clotrimazole, Fluconazole, Miconazole

5. II. On the basis of mechanism of action
Inhibits cell wall synthesis – Penicillins, Cephalosporins, Cycloserine, Vancomycin, Bacitracin
Causes leakage from cell membrane – Polypeptides (polymyxin-B, Bacitracin, Colistin), polyenes (Amphotericin-B, Nystatin, Hamycin)
Inhibit protein synthesis – Tetracyclines, Chloramphenicol, Erythromycin, Clindamycin, Linezolid
Cause misreading of mRNA code and affects permeability – aminoglycosides, Streptomycin, Gentamicin
Inhibit DNA gyrase – Fluoroquinolones (Ciprofloxacin)

6. Interfere with DNA function – Rifampin, Metronidazole
Interfere with DNA synthesis – Acyclovir, Zidovudin
Interfere with intermediary metabolism – Sulphonamides, Sulphone, paraaminosalicylic acid, Trimethoprim, Pyrimethamine, Ethambutol

7. III. Types of organisms against which primarily active
Antibacterial – Penicillins, Aminoglycosides, Erythromycin
Antifungal – Griseofulvin, Amphotericin-B, Ketoconazole
Antiviral – Acyclovir, Zidovudine, Amantadine
Antiprotozoal – Chloroquine, Pyrimethamine, Metronidazole, Diloxanide
Antihelminthic – Mebendazole, Pyrantel, Niclosamide

8. IV. According to spectrum of activity
Narrow spectrum – Penicillin-G, Streptomycin, Erythromycin
Broad spectrum – Tetracyclines, Chloramphenicol

9. V. According to type of action
Primarily bacteriostatic – Sulphonamides, Tetracyclines, Chloramphenicol, Erythromycin, Ethambutol
Primarily bactericidal – Penicillins, Aminoglycosides, Cephalosporins, Vancomycin, Ciprofloxacin, Rifampicin, Cotrimoxazole

10. VI. Antibiotics obtained from
Fungi – Penicillin, Griseofulvin, Cephalosporin
Bacteria – Polymyxin-B, Colistin, Bacitracin
Actinomycetes – Aminoglycosides, Macrolides, Tetracyclines, Polyenes, Chloramphenicol

11. Side effects of antimicrobial agents
Toxicity –
Local irritancy - gastric irritation, pain, abscess formation at intramuscular site of injection, thrombophlebitis of injected vein.
Systemic toxicity-
Aminoglycosides – 8th nerve damage and kidney damage
Tetracyclines – liver and kidney damage, anti-anabolic effects
Chloramphenicol – bone marrow depression

12. Hypersensitivity reaction Drug resistance
Rashes to anaphylactic shock
Commonly with penicllin, sulphonamide, cephalosporin
Drug resistance
Refers to unresponsiveness of microorganisms to antimicrobial agent and is akin to the phenomenon of tolerance seen in higher organisms
2 types-
Natural
Acquired