2. SULFONAMIDES
Mechanism of action
• Sulfonamide are bacteriostatic
• These agents cause competitive inhibition of bacterial folate
synthetase,an enzyme needed for incorporation of p-aminobenzoic
acid(PABA)into folic acid,a vital compound needed for bacterial growth
• Besides,it is also believed that sulfonamides,due to their structural
similarity to PABA are taken up by mistake and there is no formation of
altered folate which is metabolically injurious to the organisms concerned
4. Adverse effect
• GI irritation like nausea,vomiting,anorexia,epigastric discomfort
• Renal toxicities like crystalluria,haematuria
• Hepatitis
• Precipitation of kernicterus
• Transient myopia
Drug interaction
• Sulfonamides enchance the action of warfarin,tolbutamide,phenytoin..etc
by inhibiting their metsbolism
• It may increase the chances of toxicity
• It may counteract the efiiciency of gentamycin
5. QUINOLONES
• Quinolones are synthetic chemical compound
• The parent compound is nalidixic acid
• It is a weak antimicrobial substances
• Some newer quinolonic substances,fluoroquinolones have been developed by
introducing one or more fluorine substituents
• These are powerful antimicrobial substances
6. CLASSIFICATION OF FLUOROQUINOLONES
1ST GENERATION One fluoro substitution
eg:
ciprofloxacin,norfloxacin,ofloxacin,
pefloxacin
2ND GENERATION Additional fluoro and other
substituents
These drugs have extended spectrum
of activity
Eg:sparfloxacin,gatifloxacin,fomefloxa
cin
7. Mechanism of action
All fluoroquinolones exhibit anti-DNA gyrase activity
While multiplying,the bacteria needs DNA gyrase for division,coiling and
supercoiling of its DNA molecules
• Topoisomerase II is the homologous enzyme in mammalian cell which has a
very low affinity for fluoroquinolones and so the toxicity to host cell is
minimum
• Chromosomal mutation which produces a special type of DNA gyrase which
has low affinity for fluoroquinolones
• Permeability to the drug is reduced
8. Adverse effects
• GI irritation
• Hemolytic anemia
• Tendonitis
• Convulsion
• Hypersensitive reaction
Contraindication
• Since fluoroquinolones may cause damage to the cartilage of juvenile weight
bearing bones
• So these should not be used in children
• These should also be avoided in pregnancy and lactation
9. Drug interaction
• Antacid reduces their absorption
• H2 blockers reduce their absorption
• There is increased susceptibility of convulsion when quinolones are used
along with NSAID
• Ciprofloxacin by reducing the metabolism of theophyllinees may produce
toxicity
• Nalidixic acid and nitrofurantoins are antagonistic
10. BETA LACTAM ANTIBIOTIC
PENICILLIN
• Penicillin nucleus consist of two rings- thiazolidine and beta lactam,which
are fused together,to this nucleus,side chains are attached by an amide
linkage
11. Mechanism of action
• Beta lactam antibiotic cause damage to the bacterial cell wall
• Hence they are basically bacteriocidal agent
• They inhibit two important enzymes, transpeptidase and carboxypeptidase
which are responsible for the synthesis of peptidoglycan
• As a result rapid lysis of the cell occurs
• This lysis is augumented by activation of autolysins
Ocular penetration
• Ocular penetration of various penicillin compound is poor
• 0,5 to 1 million units of penicillin G given subconjunctivally produce
effective therapeutic level in aqueous humour and vitreous
• Probenecid also retard the pumping effect of retinal pigment epithelium
12. Adverse effect
• Penicillin shock
• Hypersensitive reaction
• Bone marrow depression
• Encephalopathy
• Spinal cord damage
Drug interaction
• Aminoglycoside should not be mixed with the penicillin in the same drip
• anticoagulant+large IV dose of penicillin;chances of bleeding as bleeding time
is prolonged
• Parenteral penicillin+heparin=there is increased chance of bleeding
• Tetracycline may hamper the bacteriocidal effect of penicillins
• Probenicid increases the haif life of penicillins
13. CEPHALOSPORINS
• They are semi-synthetic antibiotic obtained from a fungus cephalosporium
and they possess a beta lactam ring
• They are bactericidal in nature and cause damage to bacterial cellwall
• However,their mechanism of action is alittle different from that of
penicillins
Orally active compound
• 1st generation=cephalexin,cephradine,cephadroxil
• 2nd generation=cefuroxime axetil,cefaclor
• 3rd generation=cefixime
14. Adverse reaction
• Hypersensitive reaction
• Diarrhoea
• Renal toxicity
• Neutropenia and thrombocytopenia
• Thrombophlebitis
Drug interaction
• Chloramphenicol antagonizes the action of cephalosporins like ceftazidime
• Concurrent use of cephalosporin with aminoglycoside may produce
nephrotoxicity
• It potentiate the hypoprothrombinaemic effect of anticoagulants
15. MONOBACTAM
• In this group of antibiotic only beta lactam ring is present and the second
ring is missing
• Aztreonam is the classical drug in this group
CARBAPENEMS
• Imipenem is the most popular drug in this group
• It is very potent.beta lactamase resistant
• It is the broad spectrum beta lactam antibiotic
16. CHLORAMPHENICOL
• Originally it is derived from strepmyces venezuelae
• It is totally synthetically produced for commercial purposes
17. Mechanism of action
• It is mainly bacteriostatic in nature
• It gets bound to 50S ribosomal subunitand there by inhibit bacterial
protein synthesis
• Binding of aminoacyl-t-RNA to 50S ribosomal subunit is prevented
by it and thus peptide bond formation is ultimately hampered
Dosage
• In ophthalmology 0.4%-0.5% solution and 1% eye ointment usually
used for topically use
Adverse effect
• Bone marrow depression
• GI irritation
• Gray baby syndrome
18. TETRACYCLINES
• Tetracyclines are agroup of broad spectrum antibiotic
• Effective against wide variety of bacteria
• The first drug of tetracycline family is chlortetracycline was
introduced in 1948
• All members of this group are associated from soil actinomycetes
19. Mechanism of action
• Tetracycline is bacteriostatic
• They get bound to 30S ribosomes of the susceptible organisms
• And so the attachment of the aminocyl-t-RNA to m-RNA ribosome
complex is hampered leading to failure of the development of
peptide chain
• Thus the protein synthesis is inhibited
Adverse effect
• It possess Chelating property
• Anterior dentition is affected
• Inhibition of bone growth
• Hepatic damage
• Phototoxicity
• Kidney toxicity
• superinfection
20. MACROLIDS
• All macrolid antibiotic posses a large lactone ring in their chemical
structure
• Important member of this group are
erythromycin,clarithromycin,spiramycin
Mechanism of action
• All macrolids inhibit protein synthesis in bacteria by binding to 50S
ribosomal subunit
Adverse effect
• GI tract irritation can occur
• Hearing impairment
• Hypertensive reaction
• Anaphylaxis
• Steven Johnson syndrome
21. AMINOGLYCOSIDE
These are group of antibiotic obtained from soil actinomycetes
The first among this group to be discovered was streptomycin obtained
from Streptomyces griseus
Chemically all members of this grup consist of two or more amino sugar
linked glycosidically to a hexose nucleus
22. Mechanism of action
Carriage of aminoglycoside across the bacterial cell membrane:this process
requires two condition (1)oxygen supply(2)alkaline ph
Formation of wrong peptide chain due to distortion of mRNA codons
Aminoglycoside streptomycin bound to 30S ribosomes where as others may get
bound to 50S ribosomes and 30S-50S interface
Side effects
Ototoxicity
Renal toxicity
neuromuscular blockade
