Dr.Azad A Haleem AL.BrefkaniUniversity Of DuhokCollege of pharmacy

Pediatrics Departmentazad82d@gmail.com

2016

Pediatrics pharmacologyAntibiotics

ANTIBIOTICS

• Antibiotics can be defined as substances capable of killing & inhibiting the growth of micro organisms

Mechanism of action• Inhibition of cell wall synthesis : Penicillins Cephalosporins Monobactams Vancomycin• Inhibition of DNA gyrase: Quinolones • RNA polymerase Rifampicin• Inhibition of protein synthesis: Aminoglycosides Tetracyclines Erythromycin Chloramphenicol• Inhibition of folic acid metabolism: Trimethoprim Sulfonamides

Bacteriostatic vs. bactericidal drugs

• Bacteriostatic – arrest the growth and replication of bacteria at

serum levels achievable in the patient.– limit the spread of infection while the body's

immune system attacks, immobilizes, and eliminates the pathogens.

– If the drug is removed before the immune system has scavenged the organisms, enough viable organisms may remain to begin a second cycle of infection.

• Bactericidal – kill bacteria at drug serum levels achievable in the

patient. - often drugs of choice in seriously ill patients.

• It is possible for ATB to be bacteriostatic for one organism and bactericidal for another.

Antimicrobial activity

• Antimicrobial activity: the ability that a drug kills or suppresses the growth of microorganisms.

• Minimum inhibitory concentration (MIC) – the minimum amount of a drug required to inhibit

the growth of bacteria in vitro. • Minimum bactericidal concentration (MBC) – the minimum amount of a drug required to kill

bacteria in vitro

Classification of antibacterial agents

Bactericidal Bacteriostaticβ-lactam agents ErythromycinAminoglycosides TetracyclinesCo-trimoxazole ChloramphenicolVancomycin Sulfonamides

Chemotherapeutic spectra• Narrow spectrum • only against a single or a limited group of

microorganisms,• e.g. INH is active only against mycobacteria.• Broad spectrum • affect a wide variety of microbial species.• e.g. tetracycline and chloramphenicol • Alter the normal bacterial flora ???? • precipitate a superinfection of an organism, e.g., candida.

Drug resistance • growth of bacteria is not halted by the maximal level of

that antibiotic that can be tolerated by the host. • Primary• Some organisms are inherently resistant to an antibiotic • e.g., gram-negative organisms are inherently resistant to

vancomycin. • Secondary• spontaneous mutation or acquired resistance and selection. • Cross-resistance• resistant to more than one antibiotic.

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