This document discusses the classification and mechanisms of action of various classes of antibiotics. It covers cell wall synthesis inhibitors like beta-lactams (penicillins, cephalosporins, carbapenems), protein synthesis inhibitors (macrolides, lincosamides, tetracyclines, aminoglycosides), and drugs that inhibit nucleic acid synthesis (metronidazole, rifampin, quinolones). Specific antibiotics are discussed within each class, along with their indications, mechanisms of action, dosages, side effects and contraindications. The document provides an overview of commonly used antibiotics classified according to their mechanisms of action.

1. Dr. Sumona Debnath
DDV,SSMC

2. Classificatin of antibiotics according to the machanism of action:
cell wall synthesis inhibitor:
A) Beta-lactum:
a.Penicillins
b.Cephalosporins:
First generation: cephradine
cefazolin
cephadroxil
Second generation: cefuroxime
cefoxitin
cefaclor
cefotetan

3. Third generation: ceftriaxone
cefixime
ceftazidime
cefotaxime
cefpodoxime
cefoperazone
Fourth generation: cefepime
ceftobiprole

4. c.carbapenems(meropenem,imipenem,ertape-nem)
d.monobactum(aztreonam)
e.Cilastin
B)Non-betalactum: vancomycin
isoniazid,ethambutol
polymixine-B
bacitracin
cycloserin,colistin
daptomycin

5. Bacterial protein synthesis inhibitor:
Acts on 50s ribosomal subunit:
I. Macrolids(azithromycin,erythromycin,clarithromycin)
II. Clindamycin
III. Chloramphenicol
IV. Linezolid
Acts on 30s ribosomal subunit:
I. Tetracycline,doxycycline,minocycline,demeclocycline
II. Aminoglycosides(amikacin,gentamycin,tobra-
mycin,streptomycin)

6. Drugs inhibit nucleic acid synthesis
I. Metronidazole
II. Rifampicin
III. Co-trimoxazole
IV. Quinolones:
First generation: nalidixic acid
second generation: ciprofloxacin
norfloxacin
lomefloxacin

7. Third generation:levofloxacin
sparfloxacin
ofloxacin
Fourth generation:moxifloxacin
gatifloxacin
gemifloxacin

8. Therapeutic class:macrolides
Machanism of action:
Azithromycin prevents bacteria from
growing by interfering with their protein
synthesis.It binds to the 50s subunit of the
bacterial ribosome,thus inhibiting translation
of mRNA.
Dose:10mg/kg/day

9. Indication:
Uncomplicated gonorrhoea
• Chlamydial infection
• Non-gonococcal urethritis
• Chancroid
• Uncomplicated UTI
• Cervicitis
• Skin and soft tissue infection
• PID

10. Side effect:
a. Nausea,vomiting, diarrhoea
b. cholestatic hepatitis
c. Hypersensitivity
Contraindication:
a. Hypersensitivity
b. H/O hepatic dysfunctions

11. Clindamycin:
Therapeutic class:clindamycin is a chlorine
substituted derivative of lincomycine.
Machanism of action:
Clindamycin primarily has a
bacteriostatic effect.It is a bacterial protein
synthesis inhibitor by inhibiting bacterial
ribosomal translocation.It does so by binding to
the 50s rRNA of the large bacterial ribosome
subunit.
Dose:10-25mg/kg/ day.

12. Indication:
a. Acne
b. PID
c. Bacterial vaginosis
Side effect:
a. Pseudomembranous colitis
b. Erythema multiforme
c. Contact dermatitis
d. Exfoliative dermatitis
e. Urticaria

13. hypersensitivity.
Amikacin:
Therapeutic class:aminoglycosides
Machanism of action:
Amikacin binds to 30s ribosomal subunit of
susceptible bacteria thus inhibiting its protein
synthesis.
Dose:15-22mg/kg/day.

14. Organism against whice Amikacin act:
proteus
pseudomonas
enterobacter
serratia
MDR mycobacterium tuberculsis

15. Indication:
a. Skin and soft tissue infection
b. Bacterial septicemia
c. Complicated and recurrent UTI
d. TB and Non-tubercular mycobacterial
infection.
Side effect :
a. Nephrotoxicity
b. Neurotoxicity
c. Ototoxicity
d. rash and allergic reaction
e. Eosinophilia

16. Contraindication:
a. Pregnency
b. Myasthenia gravis
c. Perforated ear drum
d. Hypersensitivity
Spectinomycin:
Therapeutic class:miscellaneous antibiotic structurally related to
aminoglycosides
Machanism of action:protein synthesis inhibitor by binding with 30s
ribosomal subunit.
Dose:40mg/kg as single dose,maximum 2gm

17. Indication:
a. Gonorrhoea
b. Cervicitis
c. Proctitis
Side effect:
a. Urticaria
b. Alteration of kidney and liver function
c. Decrease in Hb and haematocrite
Contraindication:
hypersensitivity

18.  Ofloxacin:
Therapeutic class:quinolone
Machanism of action:
oflxacin is a fluoroquinolone whice inhibit
bacterial topoisomerase lV and DNA gyrase
enzyme required for DNA
replication,transcription,repair and
recombination
Dose:400mg single or bd according to indication

19. Indication:
a. Leprosy
b. Skin and soft tissue infection
c. Non-gonococcal cervicitis
d. Complicated UTI
e. Uncomplicated gonorrhoea
f. PID
g. Septicaemia

20. Side effect:
a. Insomnia
b. Rash and pruritus
c. Vaginitis
d. Visual disturbance
Contraindication:
a. pregnency,lactation
b. Long QT interval

21. Levofloxacin:
Therapeutic class:quinolones
Machanism of action:
same as ofloxacin
Dose:10mg/kg/day
Indication:
a. UTI
b. Chronic bacterial prostatis
c. RTI

22. Side effecct:
a. Rash,pruritus
b. Headache
c. Constipation
d. Cardiac arrest
Contraindication:
a. Hypersensitivity
b. Child less than 18 year

23. Moxifloxacin:
Therapeutic class:quinolone
Machanism of action:same
Dose:400mg/day,duration according to indication
Indication:
Skin and soft tissue infection

24. Side effect:
a. Stevens-johnson syndrome
b. TEN
c. Hepatitis
d. Prolong QT interval
Contraindication:
a. Patient with prolong QT interval
b. Hypersensitivity

25. Cefadroxil:
Therapeutic class:
Frist generation cephalosporin
Machanism of action:
cephadroxil binds to one or more of the
penicillin binding protein which inhibit the
final transpeptidation step peptidoglycan
synthesis in bacterial cell wall thus inhibiting
biosynthesis and arresting cell wall assymbly
resulting in bacterial cell death

26. Dose:30-50mg/kg/day
Indication:
a. Skin infection
b. Pharyngitis
Side effect:
a. Diarrhoea
b. SJS
c. Pseudomembranous colitis
Contraindication:
hypersensitivity

27. Cefaclor:
Therapeutic class:second generation cephalosporin
Machanism of action:
cell wall synthesis inhibitor
Dose:20-40mg/kg/day
Indication:
a. Skin and skin structure infection
b. Septicaemia
c. UTI
d. pharyngitis

28. Side effect:
a. Eosinophilia
b. Rash
c. SJS
d. Pseudomembranous colitis
Contraindication:
hypersensitivity

29. Cefodroxime:
Therapeutic class:Third generation
cephalosporin
Machanism of action:cell wall synthesis inhibitor
Dose:20-40mg/kg/day
Indication:
a. Septicaemia
b. UTI

30. Side effect:
a. Rash
b. SJS
Contraindication:
hypersensitivity

31. Cefixime:
Therapeutic class:Third generation cephalosporin
Machanism of action:cell wall synthesis inhibitor.
Dose:8mg/kg/day
Indication:
a. Gonococcal urethritis
b. Typhoid fever

32.  Side effect:
a. Candidiasis
b. Erythema multiforme
c. SJS
Contraindication:
Hypersensitivity.

33. Ceftazidime:
Therapeutic class:Third generation cephalosporine
Machanism of action:cell wall synthesis inhibitor
Dose:90-150mg/kg/day
Indication:
a. Bacterial septicaemia
b. UTI
c. Pelvic cellulitis

34. Side effect:
a. Rash
b. Eosinophilia
Contraindication:
hypersensitivity

35. Cefdinir:
Therapeutic class:third generation cephalosporin
Machanism of action:cell wall synthesis inhibitor
Dose:14mg/kg/day
Indication:
a. Community acquired pneumonia
b. Otitis media
c. Soft tissue infection

36. Side effect:
a. Vaginal moniliasis
b. Renal and hepatic failure
c. Rash
Contraindication:
hypersensitivity

37. Cefditoren:
Therapeutic class:Third generation
cephalosporin
Machanism of action:
cell wall synthesis inhibitor
Dose:400mg bd ,duration according to
indication.

38. Indication:
a. Pharyngitis
b. Community acquired pneumonia
c. Exacerbation of chronic bronchitis
Side effect:
a. Bacterial and fungal superinfection
b. SJS
c. TEN
Contraindication:hypersensitivity

39. Tigecycline:
Therapeutic class:tetracycline
Machanism of action:
Tigecycline is a glycocycline antibiotic which
prevents protein synthesis of the susceptable
bacteria by binding to its 30s ribosomal subunit.
Dose:initial dose 100mg followed by 50mg every
12 hour,duration-according to indication

40. Indication:
a. Skin and skin structure infection
b. Complicated intra abdominal infection
Many taetracycline registance strains are susceptible to
tigecycline.
Side effect:
a. Infection
b. Pruritus
c. Rash
Contraindication:
hospital acquired pneumonia.

41. Dicloxacillin:
Therapeutic class:penicinallase registance
penicillin.
Machanism of action:
penicillanase are specific type beta-
lactamase showing specificity for
penicillins,again by hydrolysing the beta
lactum ring.Dicloxacillin is registance to
penicillanase thus preventing the bacteria to
break the beta lactum of penicillin.

42. Dose:12-25 mg/kg/day
.
Indication:
a. Impedigo
b. Cellulitis
c. Staphylococcal skin infection
d. Folliculitis
e. Boil,carbuncles
Side effect:
a. Rash
b. Nephritis
c. Abnormal LFT
Contraindication:
hypersensitivity to penicillin

43. Meropenem:
Therapeutic class:beta-lactum antibiotic
Machanism of action:
Meropenem is a synthetic carbapenem
beta-lactum antibiotic that exert its bactericidal
activity by inhibiting bacterial cell wall synthesis
in gm+ve and gm-ve bacteria though binding to
several penicillin binding proteins
Dose:60mg/kg/day

44. Meropenem act against: gram positive
gram negative
anaerobes
pseudomonas bacteria
It is more active against enterobacteriaceae
and less active against gram positive bacteria.

45. Indication:
a. Skin and soft tissue infection
b. Diabetic foot infection
c. Neutropenia
d. Sepsis
Side effect:
a. Constipation
b. Rash
c. Agranulocytosis
d. SJS
e. TEN
f. Seizure
Cntraindcation:hypersenstivity

46. Aztreonam:
Therapeutic class:beta-lactum antibiotic
Machanism of action:
Aztreonam inhibits bacterial cell wall synthesis
due to its high affinity for penicillin binding
protein3 of gm-ve bacteria.It is highly registant
to hydrolysis by many narrow spectrum beta-
lactamase
Dose:90-120mg/kg/day

47. Indication:
a. Skin and soft tissue infection
b. Septicaemia
c. Gonorrhoea
d. UTI
Side effect:
a. Pain at injection site
b. Neutropenia
c. Urticaria
d. Clostridium difficile associated diarrhoea
Contraindication:
hypersensitivity

48. Vancomycin:
Therapeutic class:Miscellaneous antibiotic
Machanism of action:
Vancomycin binds tightly to D-alanyl D-
alanine portion cell wall precursor causing
blockage of glycopeptide polymerization
which produces immediate inhibition of cell
wall synthesis and secondary damage to the
cytoplasmic membrane.

49. Dose:10mg/kg/day
Indication:
a. Serious infection caused by MRSA
b. Pseudomembranous colitis
c. Enterococcal endocarditis

50. Side effect:
a. Phlebitis at injection site
b. Nephrotoxicity
c. Red man or red neck syndrome
d. Bone merrow supression
e. Skin rash-erythema multiforme,TEN
Contraindication:
a. Hypersensitivity
b. H/O impaired hearing

51. Linezolid:
Therapeutic class:oxazolidinones
Machanism of action:
Inhibit protein synthesis by binding with 23s
ribosomal RNA of 50s subunit
Dose:30mg/kg/day
Indication:
a. Skin and soft tissue infection including MRSA
b. Vancomycin registance enterococci infections
c. MDR TB and nocardia infection

52. Side effect:
a. Thrombocytopenia
b. Tongue discoloration
c. Pseudomembranous colitis
Contraindication:
a. Uncontrolled HTN
b. Pheochromocytoma
c. Thyrotoxicosis
d. Carcinoid syndrome
e. Patient taking vasopressive
agent,SSRI,TCA,dopamenargic agent

53. 1.Penicillin:
a) Natural:
-penicillin V or phenoxymethyl penicillin
-penicillin G or benzyl penicillin
-benzathine penicillin
-procaine penicillin
b) Beta lactamase registance penicillin
-oxacillin
-dicloxacillin(dicloxin)
-flucloxacillin
-cloxacillin(loxacin)

54. c)Broad spectrum penicillin:
-ampicillin
-amoxicillin
2.cephalosporin:
First generation -cephradine(lebac)
-cefazolin
-cephadroxil(adora)
-cephalexin

55. Second generation-cefuroxime(turbucef)
-cefaclor(cefticlor)
-cefixitine
-cefotetan
3.Macrolides:
-azithromycin
-erythromycin
-clarithromycin
-roxithromycin(pedilid)
-spiramycin(spiracin)

56. 4.quinolones:
Fourth generation :moxifloxacin
gatifloxacin
gamifloxacin
Third generation :levofloxacin
ofloxacin
sparfloxacin(sparonex)
pefloxacin(peflox)

57. 5.Tetracycline:lymecycline(lymeclin)
doxycycline(doxin)
demeclocycline
tigecycline
6.vancomycin(vancomin)
7.Teicoplanin
8.fusidic acid(lucidin)
9.linezolid(linexil)
10.meropenam,imepenam,aztreonam

58. Antibiotics used in gram negative bacteria:
1.Penicillin:
Extended spectrum penicillin:
aminopenicillin
carboxypenicillin
ureidopenicillin
piperacillin

59. 2.Cephalosporines:
third generation:ceftriaxone
cefixime
ceftazidime
cefotaxime(cefotax)
cefpodoxime
cefperazone
ceftibuten(cefteria)
cefdinir(cefinir)
cefditoren(spacef)

60. Fourth generation:cefepime(inj.zopime)
ceftobiprole
Second generation cephalosporin has also some
gram negative activity.
3.Macrolides
4.Quenolones:
Frist generation:nalidixic acid(nebactil)
Second generation:norfloxacin
ciprofloxacin
ofloxacin
lomefloxacin(lomeflox)

61. Third generation:levofloxacin
ofoxacin
sparfloxacin
pefloxacin
5.Aminoglycosides:amikacin(amikin)
tobramycin(indobac)
gentamicin
netilmicin
streptomycin
Structurally related to aminoglycosides:
neomycin
kanamycin
spectinomycin(tinobac)

62. 6.Tetracycline
7.Clindamycin
8.meropenem,imepenem,aztreonam