Rational use of Antibiotics

Voodoo or science?

Antibiotics

2nd most commonly prescribed drugs

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

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

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

Questions Is it infection? Is it bacterial infection? If yes, take appropriate samples first

What is likely etiologic agent? What antibiotic?

Empiric antibiotic

Choice depends on: Severity of infection Susceptibility of presumed bacteria Patient factors Drug factors Cost

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

contd.

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

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

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

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

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.

Drug factors Bactericidal: cell-wall active agents e.g. beta-

lactams, aminoglycosides, Vanco. or DNA active agents e.g. Quinolones

Bacteriostat ic: 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 concentrat ion dependent ki l l ing

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

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

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

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