Transcript misuses of antibiotics

DEFINITION
Chemical substances produced by various
microorganisms ( bacteria, fungi,
actinomycetes ) that have the capacity to
inhibit or destroy other microorganisms.
They either kill bacteria(bactericidal) or keep
more bacteria from growing(bacteriostatic).
Antibiotics will not cure infections caused
by viruses.
HISTORICAL BACKGROUND
Discovery of sulfonamides in 1935 by Domagk
Clinical use of sulfonamides in 1936
Discovery of penicillin in 1928 by A. Fleming
Purification of penicillin by H.Flory&E.chain(1940)
Production of penicillin in 1941
Antibiotics are the 2nd most commonly used drugs
They cost approx. $15 billion /year ( U.S. ).
25%-40% of hospitalized pts receive one or more
courses of antibiotics ( China 79% )
In the west, 30% of drug prescription for out-pts are for
antibiotics, more than 70% in China.
They become among the most misused drugs.
Misuses of Antibiotics
50% of antibiotic use is inappropriate
7 out of 10 Americans receive antibiotics for
common cold
>90% of Antibiotics are available w/out
prescriptions in 3rd world countries
Some types of bacteria in Asia no longer
respond to 1st line drugs (WHO).
Resistance rates in several Asian countries
are the highest in the world (WHO).
Some physicians are given financial
incentives to prescribe
Antibiotics are used as growth promoters in
animals.
MISUSES OF ANTIBIOTICS
A consequence of many factors:
1- Availability of a very wide selection
2- Limitation of physician’s time
3- Physician shortage and expenses
4- Availability without prescription in pharmacies
3- Public demand ( pressure to prescribe )
4- Pts do not take them according to their
doctor’s instructions.
5- Some pts save unused antibiotics for another
illness, or pass to others.
MISUSES OF ANTIBIOTICS
1- Treatment of untreatable infections
e.g. viral infections
2- Improper dosage
3- Therapy of fever of unknown origin
4- Reliance on chemotherapy with omission
of surgical drainage
5- Lack of adequate bacteriological
informations
Antibiotic Prescription
Clinical situation
Microbiological
information
Pharmacological
consideration
Bacteriological informations
Advantages
1- The exact antibiotic to be used
2- The most effective and reject the one
with little or no activity
3- The least toxic
4- The cheapest
Disadvantages
Occasionally these tests do not parallel invivo
sensitivity
2- do not take in consideration certain sites of
infection
3- some bacteria cannot be cultivated or take time
to grow
( e.g. M.Leprae, M. Tuberculosis )
4. Bacteriological services are not available at all
hospitals
1-
BACTERIAL RESISTANCE
Definition
Conc of drug required to inhibit or kill the
bacteria is greater than the conc that can
safely be achieved in the plasma.
Examples
Mechanism of Antibiotic Resistance
1. Inactivation by enzyme produced by
bacteria
2. Reduced bacterial permeability to
antibiotic
3. Bacteria develops an altered receptor for
the drug
4. Bacteria develops an altered metabolic
pathway
5. Bacteria develops an altered enzyme
Prevention of Resistance
*Use antibiotics only when absolutely required
*Use only in adequate dosage for sufficient
period of time
Not too brief therapy
Not too prolonged therapy
( exceptions, eg. TB )
*Combination of antibiotics may be required to
delay resistance ( eg. TB )
Choice of Antimicrobial Drugs
1. Clinical diagnosis eg. Syphilis
2. Bacteriological identification
a) infecting organism is not
identified.eg.bronchopneumonia,
UTIs,meningitis.
b) infecting organism is identified but
sensitivity to antibiotic isn’t known e.g.
T.B
3. Site of infection
Choice of Antimicrobials ( Cont.)
4. Host factors
a) Genetic factors
eg. Patients with G-6-PD deficiency treated with sulf. and
chloramphenicol--- Hemolysis
b) Pregnancy and Lactation
Aminoglycosides- hearing loss in the child
Tetracyclines- injury to the developing teeth( child )
Fatal acute fatty necrosis of the liver ( preg. Mother )
c) Age of the patient
eg. Grey baby Syndrome-chloramphenicol
Discolouration of teeth-tetracycline
d) Renal function
eg. Aminoglycosides, Vancomycin in renal failure
e)Liver function
eg. Erythromycin, Chloramphenicol in hepatic failure
Choice of Antimicrobials ( Cont.)
5. Drug Allergy
6. Potential Side Effects
Chloramphenicol ( a plastic anaemia)
Tetracyclines in children (dental discol.)
Flouroquinolone in children &pregnancy
( tendon dammage )
General Principles of Chemotherapy
1. Administer drug in full dose, at proper interval and
best route
by the
2. Apparent cure achieved-continue for about 3 days further to avoid
relapse ( exception TB and bacterial endocarditis )
3. Skipping doses may decrease effectiveness of treatment & increase
the likelihood of bacterial resistance.
4. Two or more antimicrobials should not be used without
good
reason, eg.:
Mixed bacterial infections
Desperately ill patient of unknown etiology
To delay emergence of resistance (eg. TB )
To achieve synergism
eg.piperacillin+gentamicin(p.aeruginosae)
General principles ( Cont. )
Disadvantages of multiple antibiotics
Increased risk sensitivity or toxicity
Increased risk of colonization with a resistant
bacteria
Possibility of antagonism
Higher costs
4. In some infections bacteriological proof of cure is
desirable ( eg. TB, UTI )
5. Measurement of plasma conc. of antibiotics is seldom
needed, except.streptomycin in renal TB; I.M
gentamicin
Indications for antibiotics prophylaxis
Surgical prophylaxis
To prevent postoperative infections
Immunosuppressed Patients
Very old, very young
Diabetics
Anaemics
AIDS pts
Cancer pts
Dental procedures
Pts with total joint replacements
Pts with cardiac abnormalities
To prevent bacterial endocarditis
Reasons for failure of chemotherapy
1.
2.
3.
4.
5.
6.
Wrong diagnosis
Wrong choice of drug
Wrong dose
Development of resistance
Infection with more than one organism
Presence of pus