Younas Masih
RN, Post RN BSc.N
(Lecturer )
New Life College Of Nursing Karachi
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Antimicrobial medications
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Objectives
 By the end the unit students will be able to:
 1. Discuss and review common terms and concepts
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related to antimicrobial therapy.
2.Discuss mechanism of action and indication of using
antimicrobial therapy.
3. State appropriate nursing implications for a client
receiving antimicrobial drugs.
4. Discuss general principles and consideration related
to antimicrobial therapy.
5. Calculate the drug dosage for oral and parental
antimicrobial drugs.
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Terms
 Antimicrobial agent
 It is a chemical substance derived from a biological
source or produced by chemical synthesis that kills or
inhibits the growth of microorganisms.
 Before antimicrobials, large number of people died
from common illnesses
 Now many illnesses easily treated with antimicrobials
 However, many antimicrobial drugs are becoming less
useful.
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Antimicrobial drugs
 Different types of antimicrobial drugs:
 Antibacterial drugs
 Antifungal drugs
 Antiprotozoan drugs
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Antibiotics
 Antibiotic
 It is a chemical substance produced by a
microorganism that inhibits the growth of or kills other
microorganisms.
Or
 A chemical substance derivable from a microorganism
or produced by chemical synthesis that kills or inhibits
microorganisms and cures infections.
1. Bacteriostatic: inhibit growth of microorganisms
2. Bactericidal: Kill microorganisms
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Sources of Antibacterial Agents
 Natural - mainly fungal sources(The original
antibiotics were derived from fungal sources. These
can be referred to as “natural” antibiotics) e.g.
Benzylpenicillin and Gentamicin are natural
antibiotics
 Semi-synthetic - chemically-altered natural
compound (developed to decrease toxicity and
increase effectiveness). E.g . Ampicillin and
Amikacin are semi-synthetic antibiotics
 Synthetic - chemically designed in the
lab(bacteria are not exposed to the compounds
until they are released. They are also designed to
have even greater effectiveness and less toxicity).
E.g. Moxifloxacin and Norfloxacin are synthetic
antibiotics
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Mechanisms of action of
Antibacterial Drugs
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Inhibit cell wall synthesis
Inhibit protein synthesis
Inhibit nucleic acid synthesis
Injury to plasma membrane
Inhibit synthesis of essential metabolites
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Mechanisms of Action
 -Antibiotics operate by inhibiting crucial life
sustaining processes in the organism: the synthesis of
cell wall material the synthesis of DNA, RNA,
ribosomes and proteins.
 Target
 The target of the antibiotic should be selective to
minimize toxicity…but all antibiotics are toxic to some
degree!
 Harm the bacteria, not the host
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Bacterial cell
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Staining and Identification
 Gram Staining
 In this procedure bacteria are washed with a
decolorizing solution after being dyed with crystal
violet. On adding a counterstain such as safranin or
fuchsine after washing,
 Gram-negative bacteria are stained red or pink
 Gram-positive bacteria retain their crystal violet dye.
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Spectrum of Activity
 Antimicrobial medications vary with respect to the
range of microorganisms they kill or inhibit
 Narrow-spectrum antimicrobial (Some kill only
limited range) :
 Broad-spectrum antimicrobial (While others kill
wide range of microorganisms)
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Adverse Effects
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Allergic Reactions: some people develop
hypersensitivities to antimicrobials
Toxic Effects: some antimicrobials toxic at high
concentrations or cause adverse effects
Suppression of normal flora: when normal flora
killed, other pathogens may be able to grow to high
numbers
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Selection of the appropriate
antibiotic
 It depends upon
 knowledge of organism’s natural resistance
 pharmacological properties of the antibiotic toxicity,
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binding,
distribution, absorption achievable levels in blood,
urine
previous experience with same species
nature of patients underlying pathology
patient’s immune status
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Ideal Antibacterial
 Selective target – target unique
 Bactericidal – kills
 Narrow spectrum – does not kill normal flora
 High therapeutic index – ratio of toxic level to
 therapeutic level
 Few adverse reactions – toxicity, allergy
 Various routes of administration – IV, IM, oral
 Good absorption
 Good distribution to site of infection
 Emergence of resistance is slow
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Effects of Combining Drugs
1. Combinations are sometimes used to fight
infections
2. Synergistic: action of one drug enhances the
activity of another or vice versa.
3. Antagonistic: activity of one drug interferes with
the action of another.
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