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7/31/2019 Anti-Infectives and Antibiotics
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Antibiotics
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Anti-infective agents
Drugs that are designed to act onselectively on foreign organisms or cells
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Anti-infective agents
Classifications of anti-infective agentsaccording to the organisms they are
designed to kill1. antibacterial or antibiotics2. antifungals3. antiprotozoals4. antihelmintics5. antivirals
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Anti-infective agents
Classifications of anti-infective agentsaccording to their mechanism of action
1. inhibit of cell wall synthesis2. inactivate certain microbial enzymes3. inhibit protein synthesis by
destroying ribosomes4. interfere with DNA synthesis5. alter cell membrane permeability
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Anti-infective agents
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Anti-infective spectrum of
activityRefers to its effectiveness againstdifferent types of microorganisms
Narrow-spectrum anti-infectives areeffective against a few or specificspecies of pathogens
Broad-spectrum anti-infectives areeffective against a wide array ofmicroorganisms
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Anti-infective spectrum of
activityThe main goal of anti-infective therapyis to reduce the population of the
invading microorganisms to a level atwhich the immune system can take careof the infection
Anti-infective treatment in an immunecompromised host is useless
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Microorganisms may develop resistance in anumber of ways including the following
1.producing enzymes that can deactivate thedrug2.changing cellular permeability3.
altering binding sites on ribosomalmembranes
4. producing chemicals that can antagonize thedrug
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To prevent emergence of resistant strains ofmicroorganisms
1.drugs should be given at the recommendeddose
2.duration of therapy should be long enough toeradicate the population of invaders
3.doses should be spread at even intervals toinsure that critical concentrations aremaintained.
4. anti-infectives should only be used when
indicated
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Adverse reactions to
antibioticsMost common adverse reactions to anti-infective therapy
1.kidney damage (oliguria, anuria, edema)2.gastrointestinal toxicity (nausea andvomiting, diarrhea)
3.neurotoxicity (CN VIII damage vertigo,loss of hearing)4.hypersensitivity reactions
5. superinfections
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Antibiotics
anti-bacterial drugs
Two basic types of antibiotics according
to their effects on cells
1. bacteriostatic agents preventbacterial growth
2. bactericidal agents kill bacterial cells
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Antibiotics
Two types of bacterial cells according tocell wall composition
1.gram positives skin, respiratory tract2. gram negatives gastrointestinal (GI)
and genitourinary (GU) tract
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Antibiotics
Major groups of antibiotics according totheir chemical structure and mechanism
of action1. aminoglycoside2. cephalosporin3. fluoroquinolone4. macrolide5. lincosamide
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Antibiotics
Major groups of antibiotics according to theirchemical structure and mechanism of action
6. monobactam7. penicillin
8. penicillinase resistant
9. sulfonamide10. Tetracycline
11. anti-mycobacterial (anti-TB and anti-leprotic)
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Drugs under this class: amikacin, gentamicin,kanamycin, neomycin, streptomycin and
tobramycinMechanism of action (MOA): Bactericidal,inhibit protein synthesis
Spectrum: gram negatives (P.aeruginosa,E.coli, Proteus, Klebsiella-Enterobacter-Serratia, Citrobacter), gram positive(S.aureus)
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Pharmacodynamics: poorly absorbed via GIT,parenteral administration is preferred
Adverse effects: CNS (ototoxicity) renal,hepatic toxicity
Contraindications: known allergy to this drug,patients with documented renal or hepaticdisease, with active mycobacterial or herpeticinfection, CNS disorders like parkinsonismand myasthenia gravis
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Drug-drug interaction: toxic effects areincreased by CNS drugs, diuretics
Synergistic bactericidal effect withcephalosporins, penicillins andpenicillinase resistant pens
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4 generations of drugs under this class
1st gen: cefadroxil, cefazolin, cephalexin
largely effective against gram pos andsome gram negs
2nd gen: cefaclor, cefoxitin, cefuroxime
less effective against gram pos but withextended gram neg coverage
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4 generations of drugs under this class
3rd gen: cefoperazone, ceftazidime,
cefotaxime, ceftriaxone weak againstgram pos, potent against gram neg
4th gen: cefepime, cefixime broad
spectrum with good gram pos and negcoverage
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MOA: Bacteriostatic at low dose,Bactericidal, inhibit bacterial cell wall
synthesisPharmacodynamics: well absorbed viaGIT
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Adverse effects: relatively safe with non-specific side effects, Pseudomembranous
colitis (GI mucosal inflammation withhemorrhage) is a rare but severecomplication
Contraindications: known allergy to this drug
Drug-drug interaction: alcohol (disulfiram-likereaction), anticoagulants
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Ciprofloxacin, gatifloxacin, levofloxacin,moxifloxacin, norfloxacin, ofloxacin,
sparfloxacinMOA: inhibit DNA synthesis
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Spectrum: Broad spectrum, for
treatment of GUT and atypical RTI
Pharmacodynamics: well absorbed inGIT
Adverse effects: photosensitivity,suppression of bone marrow activity
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Contraindications: allergy, pregnant andlactating women, infants, children and
adolescentsDrug-drug interaction: potentiate theeffect of cardiac drugs and theophylline,
absorbed poorly if given with sucralfate,iron salts, mineral supplements andantacids
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Erythromycin, azithromycin,clarithromycin
MOA: Bacteriostatic, bactericidal,interferes with protein function
Spectrum: broad, treatment of RT, GUT,
GIT infections, used for patients whoare allergic to penicillin
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Contraindications: fungal and viralinfections, pregnancy and lactation
Adverse effects: non specific andrelatively rare
Drug-drug interaction: increases serumlevels of digoxin, anticoagulants andtheophylline, should be given on emptystomach
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Clindamycin, lincomycin
MOA: similar with macrolides
For treatment of severe skin, GUT, GITinfections
More toxic than macrolides
Adverse effects: Pseudomembranouscolitis, bone marrow depression
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Aztreonam
MOA: interferes with cell wall synthesis
Spectrum: mostly for gram pos but iseffective against some gram neginfections as well, used among patients
who are allergic to penicillins andcephalosporins
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Contraindications: allergies, pregnancyand lactation
Adverse effects: rare, mild and nonspecific
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Penicillinase: enzyme produced by penicillinresistant gram pos bacteria which can
inactivate the drugPenicillins G, V
Extended spectrum penicillins: Amoxicillin,ampicillin, carbenicillin, ticarcillin
Penicillinase resistant antibiotics: dicloxacillin,nafcillin and oxacillin
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MOA: interferes with cell wall synthesis
Spectrum: for treatment of most gram
pos infections
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Contraindications: allergy
Adverse effects: Hypersensitivity and
anaphylaxis, GIT symptoms
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Cotrimoxazole (trimethoprim-sulfamethoxazole), sulfadiazine,
sulfasalazineMOA: inhibit folic acid synthesis byblocking PABA
Pharmacodynamics: well absorbed inGIT
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Spectrum: for treatment of susceptible
GUT including trachoma and RTinfections
Contraindications: pregnancy and
lactation, TERATOGENIC!
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Adverse effects: GI disturbance, Renaland hepatotoxicity, Dermatological
including Stevens Johnson syndrome(SJS)
Drug-drug interaction: increases
hypoglycemic effect of antidiabeticdrugs
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Tetracycline, doxycycline, minocycline,oxytetracycline
MOA: inhibits protein synthesis
Spectrum: broad, treatment ofRicketssiae, Vibrio cholerae
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Pharmacodynamics: adequatelyabsorbed in GIT
Contraindications: children, pregnancyand lactation
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Adverse effects: direct irritation of GIT,fatal hepatotoxicity, weakening of bones
and teeth (Grey baby syndrome)Drug-drug interaction: interferes withabsorption of insulin, calcium containing
drugs/food products, bone marrowsuppression, decreases absorption oforal contraceptives