ANTI MICROBIAL DRUGS: GENERAL

CONSIDERATIONS

These are substances produced by microorganisms, chemical synthesis, & natural substance, which selectively suppress the growth of or kill other microorganisms at low concentrations…..

WHAT IS ANTIBIOTICS

Bacteriostatic agent: inhibit the growth of bacteria.. Bacteriocidal agent: directly kill bacteria…

A) chemical structure B) mechanism of action C) type of organisms against which

primarily active D) spectrum of activity E) type of action F) antibiotic are obtained from…..

Antibiotics drugs can be classified in many ways…

Sulfonamides and related drugs: sulfadiazine, sulfones, dapsone

Diaminopyrimidines: trimethoprim, pyrimethamine.

Quinolones: nalidixic acid, norfloxacin, ciprofloxacin, gatifloxacin etc

Beta lactam antibiotics: penicilline, cephalosporins

a) Chemical structure

Nitrobenzene derivatives :chloramphenicol Aminoglycosides: streptomycin, gentamycin,

amikacin, neomycin. Macrolide: erythromycin clarithromycin,

azithromycin. Lincosamine: lincosamycin; clindamycin Glycopeptide: venconamycin Oxazolidinone : linezolid Polypeptide:polymyxin b Nitrofuran : nitrofurantoin ,

Nitroimidazoles: metronidazole, tinidazole Nicotinic acid: isoniazid, pyrazinamide, Polyene : nystatin, amphotericin –b Azole derivatives: Others: rifampin , cycloserin, ethambutol, etc

1) inhibit cell wall synthesis 2) cause leakage from cell membrane 3) inhibit protein synthesis 4) cause misreading f m RNA code and

affect permeability 5) inhibit DNA gyrase 6) interfere DNA fuction, syntesis 7) interfere in metabolism

b) Classification on the basis of mechanism of action

1) antibacterial : penicillins , aminoglycosides,

Erythromycin 2) Antifungal : griseofulvin, amphotericin b,

ketoconazole etc 3)Antiviral : acyclovir , zidovudine,

amantadine. 4) antiprotozol : chloroquine,

metronidazole…. 5) anthelmintic: mebendazole

Types of organisms against which primarily active

A)Narrow spectrum: penicilline g, streptomycin, erythromycin,

B)broad spectrum: tetracyclines, chloramphenicol

d)Spectrum of activity

A) fungi: penicilline, cephalosporin , griseofulvin

B) bacteria: polymycin b C) actinomycetes: macrolides, polyenes,

aminoglycosides, tetracyclines, chloramphenicol…..

Antibiotic are obtain from

1) toxicity A) local irritancy. B) systemic toxicity 2) hypersensitivity reaction 3) drug resistance

PROBLEMS THAT ARISE WITH THE USE OF AMAs

A) drug tolerant: B) drug destroying C) drug impermeable D) cross resistance

Drug resistance

4) Super infection ( suprainfection) 5) nutritional deficiencies 6) masking of infection

1) patient factors Age Renal and hepatic function Local factors Drug allergy Impaired host defence Pregnancy Genetic factors

Choice an antimicrobial agent

Clinical diagnosis itself directs choice of the AMA

A good guess can be made Choice to be based on bacteriological

examination

Organism –related consideration

Spectrum of activity Type of activity Sensitivity of the organism Relative toxicity Pharmacokinetics profile Route of administration Evidence of clinical efficacy cost

DRUG FACTORS

To achived synergism:eg Penicilline+ sulfonamide Penicilline+ gentamycin Steptomycin + tetracycline Rifampin+ dapsone To reduced severity or incidence.: Amphotericin b+ rifampin…

COMBINED USE OF ANTIMICROBIALS

To broaden the spectrum of antimicrobial action

Treatment of mixed infection Initial treatment of severe infection Topicallly

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