1. Rational use of Antibiotics
Voodoo or science?

2. Antibiotics
2nd
most commonly prescribed
drugs

3. Voodoo
 A patient with fever & deranged LFT, on
Magnex & Tinidazole, shifted to hospital
 Started on Cefaxone/Oflox/Ampi/Metro
 Switched to Aug/Pip.tazo/O/M
 Switched to Clinda/P.t/O & antimalarials
 All within 48 hours of admission &
with MP reported negative

4. Facts
 50% antibiotics are used inappropriately
 Majority of acute diarrhea and acute
bronchitis episodes are not due to bacterial
infection
 UGI bleed and seizures are not due to
bacterial infection
 Antibiotics do not treat the patient, antibiotics
treat bacterial infection

5. Antibiotics
 Penicillins
 Cephalosporins
 Carbapenems
 Monobactams
 Aminoglycosides
 Quinolones
 Macrolides
 Tetracyclines
 Vancomycin
 Linezolid
 Teicoplanin
 Clindamycin
 Co-trimoxazole
 Metronidazole
 Chloramphenicol
 Rifampicin
 Nitrofurantoin
 Topical antibiotics :
Mupirocin, Polymyxin-B,
Bacitracin, Neomycin

6. Questions
 Is it infection?
 Is it bacterial infection?
 If yes, take appropriate samples first
 What is likely etiologic agent?
 What antibiotic?

7. Empiric antibiotic
Choice depends on:
 Severity of infection
 Susceptibility of presumed bacteria
 Patient factors
 Drug factors
 Cost

8. Severity
Oral antibiotic
 Always prefer
 Relatively mild infection
 After response to parenteral antibiotic
 Lower cost
 Lesser side-effects
 Increased acceptance
contd.

9. Severity
Parenteral antibiotic
 Severe infection or critically ill patient
 Ineffective oral antibiotic
 Large dose required
 Ensure bioavailability-
 Poor GI absorption
 UGI distress
 Meningitis/Endocarditis
 Costlier, more side-effects

10. Susceptibility of bacteria
 Aerobic gram-positive-
 Oral: Amox, Clox, Cephalexin, Co-trimox.
 IV: 1st
/3rd
gen. Cephalo., Vancomycin
 Aerobic gram-negative-
 Oral: Co-trimox., Quinolones
 IV: 3rd
gen. Cephalo., Pip.tazo, Aztreonam
 Anaerobes
 Oral/IV: Metronidazole, Clindamycin

11. Antibacterial spectrum of antibiotics
 Predominantly Gram positive
 Clox, Pen. G, 1st
gen. Ceph., Clindamycin
Vancomycin, Linezolid, Teicoplanin
 Only Anaerobes
 Metronidazole, Clindamycin
 Only Gram negative
 Aminoglycosides, Cipro/Oflox, Aztreonam
 Broad spectrum
 Augmentin, 3rd
gen. Ceph., Pip.tazo, Levoflox, Imipenem,
Meropenem, Chloramphenicol

12. Empiric antibiotics
 Severe acute GE: Cipro./Co-trimox.
 Acute UTI : Co-trimox./Cipro.
 Acute bronchitis : Co-trimox./Doxy./Azithro.
 Sepsis: 3rd
Cephalo/Pip.tazo/Meropenem
add Aminoglycoside
 IV line infection: Vancomycin/Linezolid

13. Patient factors
 h/o allergy
 Pregnancy: avoid Aminoglycosides & Doxycycline
 Deranged LFT: dose adjustment of Ceftriaxone, Clindamycin,
Metronidazole
 Deranged RFT: dose adjustment of Aminoglycosides,
Quinolones, Co-trimox., Vancomycin, all beta-lactams
 Deranged RFT: no dose adjustment of Ceftriaxone, Azithro.,
Clinda., Doxy., Metro.

14. Drug factors
 Bactericidal: cell-wall active agents e.g. beta-
lactams, aminoglycosides, Vanco.
or DNA active agents e.g. Quinolones
 Bacteriostatic: inhibit protein synthesis
e.g.Macrolides, Co-trimox., Doxycycline, Clindamycin
 No difference in an immunocompetent host, but
bactericidal agents preferred in an
immunocompromised host or for
meningeal/endocardial/endovascular infections
 Aminoglycosides & Quinolones show concentration
dependent killing

15. Combination of antibiotics
 Multiple potential pathogens-
intra-abdominal abscess, diabetic foot infection,
aspiration pneumonia, neutropenic fever,
septic shock
 Synergism:
 Block sequential steps in metabolism- Co-trimox.
 Inhibition of enzyme activation- beta-lactam & beta
lactamase inhibitor
 Increase uptake- beta-lactams & aminoglycoside
 Decrease emergence of resistance:
Pseudomonas

16. Side-effects of drugs
 Ceftriaxone- cholecystitis
 Imipenem- seizures
 Vancomycin- Red man syndrome, mild nephrotoxicity
 Aminoglycosides- nephrotoxicity & ototoxicity
 Macrolides- UGI distress
 Clindamycin- GI distress, diarrhoea
 Doxycycline- phototoxicity, teeth discoloration
 Metronidazole- metallic taste, stomatitis,
seizures/encephalopathy with deranged LFT
 Co-trimoxazole- allergy, photosensitivity, raised Cr.
 Chloramphenicol- BM suppression, Grey baby syndrome

17. Cost x 5 days- oral & IV- Rs.
 Augmentin- 550
 Clindamycin- 360
 Linezolid- 750
 Ciprofloxacin- 90
 Ofloxacin- 50/95
 Levofloxacin- 360
 Cefuroxime- 360
 Augmentin- 2750
 Clindamycin- 1800
 Linezolid- 5000
 Ciprofloxacin-1000
 Ofloxacin- 1550
 Levofloxacin- 1000
 Cefuroxime- 1665

18. Better use of Antibiotics
 Use when required, i.e. do not use when not required
 Empiric antibiotics based on empiric bacteria & local
susceptibility profile
 Use only necessary & appropriate combination
 Newer doesn’t mean better
 Scale up/down based on lab. results
 Switch from IV to oral ASAP
 Drugs can cause fever & can change hematologic
parameters