2. Learning objectives:
At the end of this session, YOU should be able to:
1. Understand the general principles of infectious
disease chemotherapy.
2. Understand the pharmacology of different classes
of chemotherapeutic agents
3. Apply principles of chemotherapy to treatment of
infectious diseases
3. Introduction
What is Chemotherapy?
application of drugs that are 'selectively toxic' to
invading prokaryotic micro-organisms while having
minimal effects on the host
Principle also applied to cancerous cells
4. Chemotherapy includes:
1. Antimicrobial agents:
Antibacterial drugs
Antifungal drugs
Antiviral drugs
N.B: - Antibiotics are antimicrobial agents derived from living organisms.
6. General Principles of Chemotherapy
1. Targeted treatment: Chemotherapeutic agents should
only be given when necessary and after confirmatory
susceptibility test whenever possible;
2. Pharmacokinetics of the drug should be taken into
consideration in association with hepatic and renal
functions of the patient
7. General Principles of Chemotherapy
3. MIC: Effective dosing of chemotherapeutic agent requires
attainment of MIC for antimicrobial effect
•(MIC) – The MIC is defined as the lowest
concentration of antibiotic that completely inhibits
growth of the specific organism being tested.
4. Avoid relapse: continue antimicrobial agent for at least 3
days after apparent cure is achieved
5. Avoid emergence of resistant strains: administer
adequate dosage and adopting proper synergistic regimens
9. Guidelines:
Appropriate choice of chemotherapy depends on:
1. Type of infecting organism and antimicrobial
susceptibility
2. Type of infection (e.g. bacteremia, meningitis, urinary tract
infection, abscess, etc)
3. Host factors (e.g. neutropenia, immune deficiencies, concurrent
illnesses, age, drug allergies, renal function, pregnancy, etc)
10. Guidelines:
4. Antimicrobial agent (e.g., dosage, drug interactions, serum
levels and tissue penetration, potential toxicities, cost, etc)
5. Public health considerations (e.g. widespread resistance)
11. Question Time ( True or False)
2. Which one of the following host factor will influence the appropriate
choice of antimicrobial?
a. Dose
b. Resistance pertain
c. Renal function
d. Immunity
e. Urinary tract infection
12. Classification of Antibacterial drugs
1. According to effect on bacteria:
Bactericidal
Kill micro-organism and eradicate
infection with no need for body
defence mechanisms e.g. Penicillins,
Aminoglycosides, etc
Bacteriostatic
Stop growth & multiplication of
micro-organism then body defence
mechanism eradicate the infection
e.g. Tetracyclines, Chloramphenicol,
13. 2. According to spectrum of activity
Broad spectrum
Effective against both G(-) & G(+) e.g. Broad spectrum
Penicillins, Cephalosporins, Tetracyclines, Chloramphenicol,
Cotrimoxazole and Quinolones
Narrow spectrum
Effective against G(-) only (e.g. Aminoglycosides, Polymyxin,
Metronidazole, etc) or G(+) only (e.g. Vancomycin, etc) or
specific species only (e.g.antimycobacterial, etc)
14. 3. According to mode of action
Inhibitors of bacterial cell wall synthesis
e.g. β-lactam antibiotics, Vancomycin, etc
Inhibitors of protein synthesis e.g. Tetracyclines,
Aminoglycosides, Macrolides, Chloramphenicol, etc
Inhibitors of nucleic acid synthesis e.g. Quinolones
and Rifampicin, etc
Inhibitors of metabolic pathways: Folate antagonists
e.g. Sulphonamides, Trimethoprim, Co-trimoxazole, etc
Drugs affecting cell membrane permeability e.g.
Polymyxins, etc
15.
16. Questions
Inhibitor(s) of the cell wall synthesis include :
a. Tetracyclines
b. Penicillins
c. Aminoglycosides
d. Vancomycin
Inhibitor (s) of nucleic acid synthesis include
a. Quinolones
b. Chloramphenicol
c. Rifampicine
d. sulphonamides
17. Inhibitor of folate synthesis:
a. Macrolyde
b. Sulphonamide
c. Trimethoprime
d. Tetracyclines
18. Classification of antimicrobial according to
time and concentration
Time dependent antimicrobial(Concentration independent )
• Means that the rate and extent of microorganism killing remain
unchanged regardless of antimicrobial concentration
• The time-dependent killing pattern is dependent on the duration of
pathogen exposure to an antibiotic
• Exert optimal bactericidal effect when drug concentrations are
maintained above the minimum inhibitory concentration (MIC).
• Typically, concentrations are maintained at 2 to 4 times the MIC
throughout the dosing interval
19. • Examples of concentration independent antimicrobials
include: beta-lactams, vancomycin, macrolides, aztreonam,
carbapenems, clindamycin, tetracyclines,
quinupristin/dalfopristin, flucytosine, and azole antifungals
20. Concentration dependent(time independent)
• Means that the rate and extent of microorganism killing are a function
of the antimicrobial concentration (increase as the concentration
increases)
• have high concentrations at the binding site which eradicates the
microorganism
• Bactericidal action continues for a period of time after the antibiotic level falls
below the MIC
• Examples of concentration dependent antimicrobials include:
fluoroquinolones, aminoglycosides, and amphotericin B.
21. Question Time
1. Which one of the following antimicrobial agent(s) is (are)
concentration dependant?
a. Penicillin's
b. Azoles antifungal
c. Aminoglycosides
d. Vancomycin
e. Fluoroquinolones
