CHEMOTHERAPY

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CHEMOTHERAPY

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

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CLASSIFICATION OF ANTIBIOTICSACCORDING TO
MECHANISM OF ACTION

• !INHIBITION OF CELL WALL SYNTHESIS.
• INHIBITION OF PROTEIN SYNTHESIS .
• INHIBITION OF NUCLEIC ACID SYNTHESIS .
• INHIBITION OF CELL MEMBRANE FUNCTIONS .

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According to spectrum

• Narrow spectrum as penicillin G
• Broad spectrum as tetracyclines
• Extended spectrum as amoxicillin

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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 .

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Host factors in selection of antimicrobial
therapy

• Allergy or history of adverse reactions.
• Age of patient
• Pregnancy
• Genetic or metabolic abnormalities
• Renal hepatic functions
• Site of infections
• Concomitant drug therapy
• Underlying disease

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Failure caused by microorganisms

• Inactivation of antibiotics by enzymes.
• Modification of target by mutation.
• 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.

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ANTIMICROBIAL COMBINATION

• SYNERGISM1- SEQUENTIAL SYNERGISM2-INHIBITION OF
  ENZYMATIC ACTIVITY
• 3-ENHANCEMENT OF ANTIMICROBIAL UP TAKE
• ANTAGONISM

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Aim of chemotherapeutic combination

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

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Drug interactions with antibiotics

• Aminoglycosides
• Increase the effects of curare
• Increase the nephrotoxicity
  ototoxicity of loop diuretics
• 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.

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Drug interactions

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