1. Antibiotics
 Antibiotics are the chemical substances obtained from various micro
organisms
 First discovered antibiotic is Penicillin by Alaxander Flemming in 1940
 Antibiotics are used to cure diseases caused by bacteria such as pneumonia,
tuberculosis, meningities
Conditions for a substance to act as antibiotics are as follows:
 Should be effective at low concentration
 Should not have toxic side effects
 Must be effective against pathogens
 Should be stored for a long time without appreciable loss of its activity
 Should be highly stable so that it can be isolated easily and absorbed readily
 Should be available at low cost
 Should be completely eliminated from the body after its administration has
been stopped

2. Classification of antibiotics
Classification based on chemical structure:
 Cyclic structure– cyclopentane , cyclohexane and
clycloheptane derivatives
 Tetracycline antibiotics - tetracycline
 Aromatic antibiotics - Chloramphenicol
 Amino Glycoside antibiotics - streptomycin
 Macrolides antibiotics – Erythromycin.

3. Chloramphenicol
 Discovered by Ehrlich in 1947
 Obtained by culture of “Streptomyces Venezuelae”
Properties
 Stable neutral compounds
 Bitter in taste
 Sharp melting point
 Soluble in organic solvents and sparingly soluble in water
 Optically active
 Molecular formula C H O N Cl
11 12 5 2 2
 On hydrolysis it gives dichloro acetic acid & optically active base
 On reduction with Sn/ HCl followed by diazotization & coupling
with β-naphthol – orange red dye
 On acetylation in pyridine–shows the presence of two OH groups

4. Therapeutic uses
 Effective against gram +ive and gram –ive bacteria
 It’s the first broad spectrum antibiotic
 Inhibits the growth of stephalococcus, streptococcus bacillus
 Used in treatment of typhoid, pneumonia, ricketisia, urinary
tract infection, whooping cough, meningitis, plague, syphilis,
gonorrhea & dysentry
 Employed in acute infections due to Haemophilus influenza
 Can be used in the treatment of skin and eye infection
 It is absorbed in a intestinal tract and diffused into tissues.
 As it is insoluble in water it has to be administered in the form
of fine particles.

5. Structure, activity, relationship of
Chloramphenicol
Modification of para nitro phenyl group:
 If the nitro group of phenyl ring of chloramphenicol is replaced by other
substituents like CN , their physiological activity is reduced
 Shifting the nitro group from para position , reduces the anti-bacterial
activity
 If phenyl ring of choloramphenicol is replaced by alicyclic or
hetrocyclic ring, then the resulting antibiotic is found to be less effective
Modification of Dichloroacetamide chain
 If chloro group is replaced by bromo group , the antibacterial activity is
only 80% .

6. .
Modification of 1,3 propane diol
 The propane diol group is essential for its antibacterial
activity
 If the length of the propane is altered, the drug is deactivated
 If the bulkier substituents are introduced activity is
decreased
STEREOCHEMISTRY:
 cholramphenol has two asymmetrical carbon atom.
 It can form 4 optically active isomers-D & L threo isomers
and D & L erythro isomers.
 Erythro isomers- toxic & not used in medicine
 L-threo isomer-biologically inactive.
 D-threo isomer – biologically active.

7. Toxicity
Nitro group may contribute to bone marrow depression
and Fatal blood dyscrasia
Dosage
Adult dosage- 500mg every 6 hrs
MODE OF ACTION
It inhibits the growth of bacteria.
DOSAGE FORMS
available as: capsules, ear drops, eye ointment

8. Penicillin
 Widely used antibiotic
 Extracted from mould of “Penicillin notatum”
 Belongs to a group of antibiotic called β-lactam Antibiotic
 Basic structure contains thiozoline ring fused with β-lactam
ring
 Two rings constitute the fundamental nucleus of group of
antibiotics referred as “PENICILLIN”
 Chrysogunum- highest yield of penicillin

9. Therapeutic uses
 Penicillin is effective against gram +ive and gram –ive coccai and some
gram +ive bacilli
 It is bacteriostatic in action, but at certain concentration it acts as
bactericidal agents.
 Inhibits synthesis of bacterial cell wall
 Non-toxic even in large doses.
 Effective against pneumocccal infections, streptococcal infections,
staphylococcal infections, meningococcal infections.
 Used in the treatment of diphtheria, gangrene, tetanus, etc
 Used topically, orally or parentally
 In oral therapy, the dosage must be given in larger doses as it is inactivated
by gastric acids
 Sodium or potassium salt are used for injection
 Calcium salt can be used as an ointment or as powder

10. .
Adverse effects
 adverse effects like vomiting, nausea, anyphyxis and allergic
reactions
 Natural penicillin are inactivated faster by HCL acids, variety
of semi synthetic and synthetic penicillin are produced that are
made effective
 All these have allergic reactions similar to those produced by
natural penicillin.

11. Types of penicillin &Properties
Types of penicillin
 Natural penicillin
 Semi synthetic penicillin
Properties
 Optically active
 Soluble in water
 Hydrolyzed by hot inorganic acids
 Acid resistant
 Effective in treatment of respiratory tract infection, streptococcal infections
and pneumonococcal infections
 Methicillin is resistant to penicillinase and used in treatment of infection
resistant to benzyl penicillin
 Ampicillin is effective against influenza, gonorrhea, salmonella typhose, e-
coli, etc.

12. Mode of action
 Bacteriostatic and bacteriocidal
 Anti-bacterial against organism mainly their growth phase
 Interferes with synthesis of ribonucleic acid

13. Tetracyclins
Tetracyclins compress a group namely:
Tetracyclins
Chlorotetracyclins
Oxytertacyclins
 Most important anti-microbial property
 Obtained from the species of actinomyces named as streptomyces
 Precipitated from a culture medium maintained at a pH 8-10 in presence of divalent cations
 Can be separated by ion exchange chromatography

14. Therapeutic uses
 Effective against gram+ive and gram –ive micro-organisms
 Bacteriostatic
 Inhibit essential enzymes in bacterial cell
 Prevent synthesis of ribosomes
 Used in treatment of infections such as pneumonia,
actinomycosis, urinary infection, spotted fever, typhus fever,
gonorrhea, syphilis,plague, ricketisia, etc.
 Oromycin is effective against many bacteria similar to
cholorominphenicol but is not as effective as
chloramphenicol against typhoid fever

15. .
 Less toxic drug, tolerated by patients
 Tetramycin is more stable than oramycin
 Used in treatment of conjunctivitis, cholera, amoebic
dysentery, etc.
 Its effective against pneumonococci, streptococci, H-
influenza, e-coli, M-tuberculosis
 Absorbed in duodenum and small intestine
 Long duration of anti-bacterial action
 They form insoluble complexes with calcium and magnesium
 Substances like milk which contain calcium and antacids
reduce their absorption
 Not advisable for children and pregnant women

16. Chemical properties
 Yellow, odourless, crystalline powder with bitter taste
 Sparingly soluble in water
 Oxidized by oxygen in air, they darken when exposed to air
 Amphoteric in nature , basicity is due to N-amino group and
acidity is due to phenolic group
 Form chelates with metal ions
 Due to the presence of phenol, it gives colour with neutral
ferric chloride and forms azo dye
 Gives florescence in presence of UV light

17. Streptomycin
 Belongs to the important amino glycosidic group of antibiotic
 It is given the name from streptomyces
 Organism producing the antibiotic is known as “Streptomyces
Griseus”
 Other examples of amino glycosidic antibiotics are
gentamycins, neomycins

18. Therapeutic uses
 Used in treatment of tuberculosis, infections of e-coli, H-
influenza, plague, respiratory tract infection, meningities
 Bactericidal properties
 Disturbs the normal protein synthesis and bacteria

Destroyes the cell membrane

19. Properties
 Colourless solid
 Dissolves in water but soluble in organic
solvents
 Optically active and Leavoratotary
 Basic in nature

20. Structure
Streptomycin is made
up of three basic
units:
 Streptidine
 L-streptose
 N- methyl L-
glucosamine

21. Rifamycin
 It is isolated from “Streptomyces mediterranei”
 Belongs to a new class of antibiotics called “Ansamycins”
 There are five types of rifamycis A,B,C,D,E
 Cant be administered orally
 Given intravenously

22. Therapeutic uses
 Inhibits the growth of gram +ive bacteria such as e-coli, keri
bacila
 Effective against staphylococcus
 Acts by blocking the biosynthesis of nucleic acid of bacteria

Used in the treatment of tuberculosis

23. Properties
 Reddish brown crystalline powder
 Slightly soluble in water, completely in methanol
 It exist as a “zwitter ion”

24. Cephalosporins
 Isolated from the fungi “Cephalosporium acremonium” in 1948
 They are β-lactum antibiotic with same fundamental structure as penicillin
 It contains dihydro-meta thiazine ring
 Most acid stable than penicillin
Classification of cephalosporin
Cephalosporin N
Cephalosporin P
Cephalosporin C
Cephalosporin C is true cephalosporin

25. Therapeutic uses
 Used in the treatment of urinary tract infections, streptococcal
infections, pneumonia, tonsillitis, skin infections, etc.
 Inhibits cross linking of peptide units in bacterial cell wall

26. CIPROFLOXACIN
They have been divided into four generations
 This division is chronological order, the overall antibacterial
spectrum as well as potency.
 It is the most potent first generation fluoroquinolones active
against broad range of bacteria-aerobic gram -tve bacilli & gram
+tve bacteria at higher concentrations.
 important feature- tissue penetrability.

27. THERAPEUTIC USES
 Effective against urinary tract infections,typhoid,bone,soft tissue
gynaecological and wound infections,respiratory infections,
tuberculosis, meningitis and conjunctivitis
 First choice drug- typhoid cells since chloramphenicol,
amphicillil and cotrimaxazole are unreliable due to development
of resistance.
 Used as a component of combination of multi drug treatment of
tuberculosis and respiratory infections.

28. MODE OF ACTION
 It is rapidly absorbed orally but food delays absorption
 high tissue penetrability
 concentration in lung muscle and bone
Excreted by urine
ADVERSE EFFECTS
 Produces nausea, vomiting and bad taste
 Cause head aches, anxiety & insomnia,some times rashes on
the skin.
 not admistered to children- damage to weight bearing joints.

29. CARBAPENEMS
Extremely potent and broad spectrum antibiotic.
 It is a β-lactone antibiotic
 resistant to β-lactinases.
 limiting feature of imipenim is rapid hydrolysis by enzyme
peptidase located in the border of renal tubular cells.
 effective in treatment of hospital acquired infections- cancer &
AIDS
Activity include gram +tve cocci and enterobacteriaceae
It cause seizuse at higher doses.