CHEMOTHERAPY ANTIBIOTICS Chemical substances produced by microorganisms and have the capacity to inhibit or destroy other organisms. ANTIBIOTICS Chemical substances produced by microorganisms and have the capacity to inhibit or destroy other organisms. CHEMOTHERAPEUTIC AGENT CHEMOTHERAPEUTIC AGENT Synthetic chemical substances used to inhibit or destroy microorganisms. Synthetic chemical substances used to inhibit or destroy microorganisms.

CLASSIFICATION OF ANTIBIOTICS ACCORDING TO MECHANISM OF ACTION !INHIBITION OF CELL WALL SYNTHESIS. !INHIBITION OF CELL WALL SYNTHESIS. INHIBITION OF PROTEIN SYNTHESIS. INHIBITION OF PROTEIN SYNTHESIS. INHIBITION OF NUCLEIC ACID SYNTHESIS. INHIBITION OF NUCLEIC ACID SYNTHESIS. INHIBITION OF CELL MEMBRANE FUNCTIONS. INHIBITION OF CELL MEMBRANE FUNCTIONS.

According to spectrum Narrow spectrum as penicillin G Narrow spectrum as penicillin G Broad spectrum as tetracyclines Broad spectrum as tetracyclines Extended spectrum as amoxicillin Extended spectrum as amoxicillin

REASONS FOR FAILURE OF CHEMOTHERAPY. 1- WRONG DIAGNOSIS 2- WRONG CHOICE Of DRUG 3- WRONG DOSE 4-Drug RESISTANCE 5- INFECTIONS WITH MORE THAN ONE ORGANISM 6-PRESENCE OF PUS,BLOOD,NECROTIC TISSUES.

Host factors in selection of antimicrobial therapy Allergy or history of adverse reactions. Allergy or history of adverse reactions. Age of patient Age of patient Pregnancy Pregnancy Genetic or metabolic abnormalities Genetic or metabolic abnormalities Renal & hepatic functions Renal & hepatic functions Site of infections Site of infections Concomitant drug therapy Concomitant drug therapy Underlying disease Underlying disease

Failure caused by microorganisms Inactivation of antibiotics by enzymes. Inactivation of antibiotics by enzymes. Modification of target by mutation. Modification of target by mutation. Impaired penetration of drug to target,occurs only in gram-negative species. Impaired penetration of drug to target,occurs only in gram-negative species. The presence of an efflux pump produced by gram-negative organisms which transport antibiotics from the periplasm back across the outer membrane. The presence of an efflux pump produced by gram-negative organisms which transport antibiotics from the periplasm back across the outer membrane.

ANTIMICROBIAL COMBINATION SYNERGISM 1- SEQUENTIAL SYNERGISM 2-INHIBITION OF ENZYMATIC ACTIVITY SYNERGISM 1- SEQUENTIAL SYNERGISM 2-INHIBITION OF ENZYMATIC ACTIVITY 3-ENHANCEMENT OF ANTIMICROBIAL UP TAKE 3-ENHANCEMENT OF ANTIMICROBIAL UP TAKE ANTAGONISM ANTAGONISM

Aim of chemotherapeutic combination Broaden the spectrum of antibacterial activity Broaden the spectrum of antibacterial activity Reduce the doses Reduce the doses Reduce the side effects Reduce the side effects Overcome drug resistance Overcome drug resistance Produce a more potent compound ( synergism) Produce a more potent compound ( synergism) Treatment of severe infections of unknown etiology as in septicemia. Treatment of severe infections of unknown etiology as in septicemia.

Drug interactions with antibiotics Aminoglycosides Aminoglycosides Increase the effects of curare Increase the effects of curare Increase the nephrotoxicity & ototoxicity of loop diuretics Increase the nephrotoxicity & ototoxicity of loop diuretics Enzyme inhibitors as chloramphenicol & erythromycin increase the action & toxicity of other drugs as digitalis Enzyme inhibitors as chloramphenicol & erythromycin increase the action & toxicity of other drugs as digitalis Enzyme inducers as rifampin decrease the action of other drugs as oral anticoagulants or oral contraceptives. Enzyme inducers as rifampin decrease the action of other drugs as oral anticoagulants or oral contraceptives.

Drug interactions Sulphamethoxazole + trimethoprim result in bactericidal effect. Sulphamethoxazole + trimethoprim result in bactericidal effect. Sulphonamides displace oral hypoglycemic from their plasma protein binding causing hypoglycemia Sulphonamides displace oral hypoglycemic from their plasma protein binding causing hypoglycemia