Antibiotics

1. Prepared by
Dr Muhammad Ashiq Toor
DVM , Bs (Zoology)
from IUB BWP (2010 – 2015)
+92-344-499-7375
+92-300-364-2402

2. Antibiotics
Class wise , Spectrum , Bacterial activity ,
MOA & dose rates.

3. The Spectrum of Antimicrobial Activity
Narrow spectrum (limited spectrum)
 Antimicrobials effective against a (limited spectrum)
of microbial types.
 A drug effective on G+ve or G-ve bacteria.
Broad spectrum (extended spectrum)
 Antimicrobials effective against a (extended spectrum) wide
variety of microbial types .
 A drug effective against both G+ve & G-ve bacteria .

4. Broad spectrum
Some examples of broad-spectrum antibiotics include :
 Penicillin
 Cephalosporin
 Tetracycline
 Ciprofloxacin
 Levofloxacin
These drugs work on both G+ve & G-ve organisms.

5. Narrow Spectrum
Vancomycin
Azithromycin
Clarithromycin
Clindamycin
Clindamycin + Benzoyl Peroxide
Erythromycin

6. No antibiotic is effective against all
microbes

7. The Action of Antimicrobial Drugs
Bacteriocidal
 Kill microbes directly
Bacteriostatic
 Prevent microbes from growing

8. Bacteriostatic vs Bactericidal
Bacteriocidal antibiotics
Kill the target bacteria. These drugs include :
 Penicillins
 Cephalosporins
 Carbapenems
 Aminoglycosides
 Fluoroquinolones
 Nitroimidazoles

9. Bacteriostatic antibiotics
Slow down bacterial growth & allowing the host immune
system to fight the bacteria. These drugs include :
 Macrolides
 Tetracyclines
 Sulfonamides
 Clindamycin
 Chloramphenicol

10. Mechanisms of Antibiotics Action
1- Inhibition of Cell Wall Synthesis
2- Injuring the Plasma Membrane
3- Inhibition of Protein Synthesis
4- Inhibition of Nucleic Acid Synthesis
5- Inhibiting the Synthesis of Essential Metabolites

11. The Action of Antimicrobial Drugs

12. Mechanisms of Antibiotics Action Dihydrofolate

13. Mechanisms of Action:
inhibit the last step in the peptidoglycan
synthesis of the cell wall
1. inhibition of transpeptidase
 enzymes
2. activation of penicillin binding
 proteins (PBPs)
3. activation of autolysins
 (murein hydrolases)

15. Protein Synthesis

16. Inhibition of Protein Synthesis by antibiotics

17. Inhibition of Protein Synthesis by
Antibiotics
Figure 20.4

19. Inhibition of Cell Wall Synthesis
Transpeptidases, Carboxypeptidases &
Transglycosylases
Penicillin-binding proteins (PBPs(
β-Lactam antibiotics: generally are bacteriocidal agents

20. 1- Beta-Lactam Antibiotics :
 Penicillins
 Cephalosporins
2- Glycopeptides :
 Vancomycin
3- Lipopeptides :
 Daptomycin
4- Polypeptides :
 Bacitracin
Inhibition of Cell Wall Synthesis

21. 1- Aminopenicillins: Ampicillin, Amoxicillin
Ampicillin was limited primarily to Escherichia & Proteus
species .
2- Carboxypenicillins: Carbenicillin, Ticarcillin
Are effective against a broader range of G-ve bacteria i.e
Klebsiella, Enterobacter, & Pseudomonas species .
Broad-spectrum penicillins

22. Clavulanic acid, Sulbactam, Tazobactam
(ampicillin, amoxicillin, ticarcillin, piperacillin)
Amoxicillin/clavulanic acid (Co-amoxiclav)
Ampicillin/sulbactam (Sultamicillin)

23. Cephalosporins
More stable to β-lactamase hydrolysis

24. Antimicrobial spectrum of cephalosporins
Generation of
cephalosporin
s
Active towards
Gram-positive
bacteria
Gram-negative
bacteria
І +++ +/-
ІІ ++ +
ІІІ + +++
ІV ++ +++

25. CEPHALOSPORINS
CLASSIFICATION
A. First Generation
 1. Cephaloridine-Loridine, Ceporan
 2. Cephalothin-Keflin
 3. Cephalexin-Keflex, Ceporex
 4. Cefazolin-Cefacidal
 5. Cephradine-Velosef
 6. Cepharpirin-Cefadyl
 7. Cephadroxil-Doricef, Cefamox

26. Second Generation
1. Cefaclor-Ceclor
2. Cefoxitin – Mefoxin
3. Cefuroxime – Zinacef, Zinnat
4. Cefonicid – Monocid
5. Cefotetan - Cefotan
6. Cefamdandole – Mandol
7. Cefprozil – Cefzil
8. Loracarbef – Lorabid
9. Cefmetazole – Zefazone
10. Ceforanide

27. Third Generation
 1. Cefotaxime – Claforan
 2. Cefoperazone – Cefobid
 3. Moxolactam – Moxam
 4. Ceftizoxime – Cefizox
 5. Ceftriaxone – Rocephin
 6. Ceftazidime – Fortum
 7. Cefotiam – Ceradolan
 8. Cefixime – Suprax
 9. Cefetamet – Globocef
 10. Cefpodoxime – Vantin
 11. Ceftibuten – Cedax
 12. Cefdinir –Omnicef
 13. Cefditoren

28. Fourth Generation
1. Cefepime – Maxipime
2. Cefpirome – Cefrom

29. Broad-spectrum antibiotics
 Active against virtually all organisms
Imipenem, Meropenem, Ertapenem
Carbapenems

30. Narrow-spectrum antibiotics
 Are active only against aerobic & G-ve bacteria
Aztreonam
Monobactams

31.  Damage cytoplasmic membrane and inhibit RNA transcription
 The treatment of skin infections
 Used in creams, ointments, sprays
Polypeptides: Bacitracin

32.  Bactericidal
 Bind irreversibly to ribosomal proteins
Misreading of the messenger RNA (mRNA)
Premature release of the ribosome from mRNA
 Streptomycin, Neomycin, Kanamycin, & Tobramycin
Streptomyces species
 Gentamicin & Sisomicin
Micromonospora species
 Amikacin from kanamycin
Aminoglycosides

33.  Broad-spectrum
 Bacteriostatic
 Tetracycline, Doxycycline, Chlorotetracycline
 Binding reversibly to the 30S
 Blocking the binding of aminoacyl-tRNA
 Chlamydia, Mycoplasma, Rickettsia
Tetracyclines

34. Chloramphenicol
 Broad spectrum
 Bacteriostatic
 Blocking peptide elongation
 Typhoid fever

35.  Broad spectrum
 Bacteriostatic
Reversible binding to the 50S rRNA
Erythromycin, Azithromycin, Clarithromycin
Macrolides

36. Inhibition of Nucleic Acid Synthesis
1- Quinolones
2- Rifampin
3- Metronidazole

37.  Synthetic
 Inhibit bacterial DNA gyrases (II) or topoisomerases (IV)
Nalidixic acid
Fluoroquinolones:
Ciprofloxacin Levofloxacin Enrofloxacin
Quinolones

38.  Reduction of its nitro group by bacterial nitroreductase
 Producing cytotoxic compounds that disrupt the host DNA
 Anaerobic bacterial infections (B. fragilis)
Metronidazole

39. Antimetabolites
Sulfonamides
 Preventing the synthesis of the folic acid
 Compete with para-amino-benzoic acid (PABA)

40. Trimethoprim
 Blocks the conversion of dihydrofolate to tetrahydrofolate
 Inhibiting dihydrofolate reductase
 Trimethoprim + sulfamethoxazole: Synergistic combination
 Treatment of acute and chronic urinary tract infections
Antimetabolites

41. S
No Group name Spectrum Activity Examples MOA
1. Beta Lectum Broad spectrum bactericidal Penicillins
Cephalosporins
Inhibit cell wall synthesis
2. Macrolids Narrow spectrum (G
+ve)
bacteriostati
c
Azithromycin
Clarithromycin
Erythromycin
30s rRNA block
3. Quinolones Broad spectrum bactericidal Ciprofloxacin
Levofloxacin
Gatifloxacin
Inhibit bacterial DNA
gyrases
4. Tetracycline Broad spectrum bacteriostati
c
Tetracycline,
Doxycycline,
Minocycline
30s rRNA block
5. Aminoglycosides Narrow spectrum (G -
ve)
Bactericidal Streptomycin,
Neomycin,
Kanamycin, &
Tobramycin
30s rRNA block

42. S
No Group name Spectrum Activity Examples MOA
6. Chloramphenical
s
Broad spectrum Bacteriostatic Florphenicol
Achlor
Chloromycetin
Binding reversibly to the peptidyl
transferase (50S)
7. Cephalosporins Broad spectrum bactericidal Inhibition of cell wall synthesis
First-generation Narrow-
spectrum
(G +ve)
bactericidal Cefazolin
Cephalothin
Cephradine
Second
generation
expanded-
spectrum (G -
ve)
bactericidal Cefamandole,
Cefaclor,
Cefuroxime
Third generation broad-spectrum
Noscomial
diseases
bactericidal Cefixime,
Cefoperazone
Ceftriaxone

43. Fourth
generation
broad-spectrum
Covers
pseudomonal
infections
bactericidal Cefepime,
Cefpirome
Fifth generation Used to treat
MRSA
bactericidal Ceftobiprole,
Ceftaroline

44. Dose rates of Antibiotics

45. Macrolids
Erythromycin Cattle 8–15 mg/kg, IM, sid-bid
Cat 15 mg/kg, PO, tid
Foals 25 mg/kg, IM, tid
Tylosin Cattle 10–20 mg/kg, IM, sid-bid
Pigs 10 mg/kg, IM, sid-bid
7–10 mg/kg, PO, tid
Cats 10 mg/kg, IM, bid

46. Quinolone
Nalidixic acid Cats, dogs 3 mg/kg, PO, qid
Enrofloxacin Cats 5 mg/kg, PO, sid-bid
Dogs 5–20 mg/kg, PO, sid-bid
2.5 mg/kg, SC, once then
PO
Beef cattle (not veal or
dairy)
7.5–12.5 mg/kg, SC, once
2.5–5 mg/kg, SC, sid
Pigs 2.5–5 mg/kg, PO or IM, sid
Preruminant calves 2.5–5 mg/kg, PO or SC, sid
Marbofloxacin Cats, dogs 2.75–5.5 mg/kg, PO, sid
Difloxacin Dogs 5–10 mg/kg, PO, sid
Orbifloxacin Cats, dogs 2.5–7.5 mg/kg, PO, sid

47. Tetracycline
Tetracycline Cat , Dog 7 mg/kg, IM, or IV sid-bid
20 mg/kg, PO, tid
OTC Cat , Dog 7 mg/kg, IM or IV , bid
Cattle , sheep ,
pig
5-10 mg/kg, IM or IV, sid-bid
Horse 5 mg/kg, p o bid
Doxy Dog 5 - 10mg/kg, p o sid
Cats 5 mg/kg, IM, sid

48. Aminoglycoside
Gentamicin 6–12 mg/kg, IM or SC, sid
Kanamycin 25–30 mg/kg, IM or SC, sid
Streptomycin 15–25 mg/kg, IM or SC, sid
Amikacin 15–22 mg/kg, IM or SC, sid
Netilmicin 6–12 mg/kg, IM or SC, sid
Neomycin 15 mg/kg, PO, sid-bid
0.5–1 g/quarter,
intramammary, sid

49. Cephalosporin
Dosage, Route, and Frequency
Cephapirin 30 mg/kg, IM or IV, every 4–6 hr
Cefazolin 20–25 mg/kg, IM or IV, tid-qid
Cefpodoxime 8 mg/kg, SC, every 14 days
Cefovecin 5–10 mg/kg, PO sid-bid
Cephalexin 10–30 mg/kg, PO, tid-qid
Cefadroxil 22 mg/kg, PO, bid
Ceftiofur 1.1–2.2 mg/kg, IM, sid

50. Dosages of Sulfonamides
Sulfonamide Species Dosage, Route, and
Frequency
Sulfathiazole Horses 66 mg/kg, PO, tid
Cattle, sheep, pigs 66 mg/kg, PO, every 4 hr
Sulfamethazine Cattle 220 mg/kg, PO or IV, sid
Sulfadiazine All 50 mg/kg, PO, bid
Sulfadimethoxine All 55 mg/kg, PO,
Sulfaethoxypyridazine Cattle 55 mg/kg, PO, sid
Pigs 110 mg/kg, PO, sid
Sulfapyridine Cattle 132 mg/kg, PO, bid
Succinylsulfathiazole All 160 mg/kg, PO, bid

51. Examples of antibiotics available
in market

52. Almox-LA:
Composition:
Amoxicilline trihydrate 150mg
Company: Star
Medicine Form: Injectable
Dose Rate: 1m/ 10kg
Availability: 50 ml vial
Price: Rs. 250/=

53. Tylosel:
Composition:
Tylosin Tartarate 200mg
Company: Selmore
Medicine Form: Injectable
Dose Rate: 0.05ml/kg
Availability 50ml vial
Price: Rs. 221/=

54. Genton:
Composition:
Gentamycin Sulphate 100mg
Company: ICI
Medicine Form: Injectable
Dose Rate: 1ml/20kg
Availability 50ml vial
Price: Rs. 275/=

55. Diarex Forte:
Composition
Sulphadiazine 35.5mg
Sulphadimidine 28.4mg
Neomycine Sulphate 1.8mg
Hyoscine Methylbromide 0.04mg
Pectin 7.1mg
Company: zakfas Pharma
Medicine Form: Oral suspension
Dose Rate: 100ml/L.A & 50ml/ S.A
Availability 100ml pack
Price: Rs. 150/=

56. Utinol Tabs:
Composition:
Sulphadiazol 1750mg
Pencilline G 10000i.u
Streptomycine sulphate 50mg
Etinyl estradiol 0.5mg
Company: Star
Medicine Form:Intrauterine passeries
Dose Rate: 4-8/ L.A & 2-4/S.A
Availability 20 passeries per pack

57. DRUGS HALF LIFE ORAL ABS
1.short acting
Sulfacytine
Sulfisoxazole
Sulfamethizole
Short
Short (6 h)
Short (9 h)
Prompt (peaks in
1-4h)
Prompt
Prompt
2. Medium acting
Sulfadiazine
Sulfamethoxazole
Sulfapyridine
Intermediate(10-17h)
Intermediate (10-12h)
No data
Slow (peak in 4-8h)
Slow
Slow
3.Long Acting
Sulfadoxine Long (7-9 days) Intermediate

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