Transcript common therapeutics in sheep - College of Veterinary Medicine

COMMON THERAPEUTICS
IN SHEEP
Fouad Kasim Mohammad
Department of Physiology,
College of Veterinary Medicine,
University of Mosul, Iraq
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PRINCIPLES OF ANTIMICROBIAL
THERAPY IN SHEEP
Antibiotic
A substance produced by a microorganism that, at
therapeutic doses, inhibits or kills other
microorganisms.
Bacteriostatic activity
Stops multiplication of the bacteria (no killing).
All antibiotics are bacteriostatic at some
concentrations.
Some are bacteriostatic at almost all concentrations,
e.g. sulfonamides, tetracyclines.
Bactericidal activity
Killing the bacteria, when the concentration of the
antibiotic is high enough
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Antimicrobial activity may be:
1. Concentration dependent
(aminoglycosides)
2. Concentration and time
dependent (fluoroquinolones)
3. Time dependent (beta lactams).
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General Mechanisms of Action of Antimicrobial
Agents
Inhibition of
penicillins, cephalosporins,
Cell wall
bacitracin, vancomycin.
synthesis
Inhibition of
chloramphenicol, tetracyclines,
Protein
aminoglycosides, macrolides,
synthesis
lincosamides,
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Effects on Cell
membrane
Effects on
Nucleic acid
function
Effects on
Intermediary
metabolism
polymyxin, aminoglycosides,
amphotericin
nitroimidazoles, nitrofurans,
quinolones, rifampin (some
antiviral agents)
sulfonamides,
trimethoprim
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Activity of Various Antimicrobial Classes
Bacteria
Mycoplasma
Rickettsia
Chlamydia
Aminoglycosides
+
+
Beta-lactams
+
Chloramphenicol
+
+
+
+
Lincosamides
+
+
Macrolides
+
+
+
Pleuromutilins
+
+
+
Tetracyclines
+
+
+
+
Quinolones
+
+
+
+
Sulfonamides
+
+
Trimethoprim
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+
Protozoa
+
+
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Examples of Antibacterial Agents and Their Spectrum of Activity
Aerobic
Anaerobic
G (+)
G (-)
G (+) G (-)
Examples
Broad
chloramphenicol,
tetracyclines
+
+
+
+
Narrow
benzyl penicillin
G
+
±
+
±
aminoglycosides,
sulfonamides,
enrofloxacin
+
+
+
+
+
±
+
±
+
±
Intermediate carbenicillin,
cephalosporins
ampicillin,
amoxicillin
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Antibacterial combinations and interactions
Additive (2+3=5).
Synergistic (1+2=8).
(trimethoprim-sulfonamide)
(ampicillin - clavulanic acid)
(erythromycin - rifampin)
(beta-lactam -aminoglycoside)
Antagonistic (3+4=2)
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Antibacterial combinations and interactions
In general,
combining two bacteriostatic drugs
results in additive effect, combining
two cidal drugs results in synergistic
effect. Combining cidal and static
agents can result in impairment of
bacteriocidal activity.
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Therapeutic considerations
Define the anatomical location and
severity of the infective process.
The systemic inflammatory response
is the presence of two or more of:
High rectal temperature
High heart rate
High respiratory rate
Increased WBC count
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Therapeutic considerations
Dose
Determine the correct dose and interval for
the drug, the patient, and the condition.
Host immunity
In case of reduced host immunity select a
bacteriocidal agent.
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Therapeutic considerations
Short duration may lead to therapeutic
failure and re-appearance of
infection.
Long duration may increase the risk of
adverse drug reactions and may
increase resistance in bacterial
populations.
Treat 3 days after the end of clinical
signs. Some recommend a negative
culture before antimicrobial therapy
is discontinued.
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ANTHELMINTICS
Ideal anthelmintics
Broad spectrum of activity.
Non toxic to treated animals
Wide margin of safety..
Rapid metabolism and
excretion
No residues in milk or meat
Easy administration
Cost effective
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Macrocyclic Lactones
(Macrolides)
Ivermectin
Eprinomectin
Doramectin
Moxidectin
Milbemycin oxime
Selamectin
Bind to chlorine channels causing
paralysis
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Benzimidazoles
Thiabendazole
Mebendazole
Fenbendazole
Oxfendazole
Oxibendazole
Albendazole
Interfere with energy metabolism by
inhibition of polymerization of
microtubules
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Imidazothiazoles
Tetramisole
Levamisole
Cholinergic agonists
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Routes of administration
Oral (suspension, feed mix)
Injection (SC)
Topical (pour on)
Slow release (intraruminal
sustained release devices)
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Intraruminal sustained release devices
They allow a slow release of active
drug over a period of time, usually
the complete grazing season. The
aim is to prevent establishment of
nematode populations in hosts
during periods of maximum
availability of third stage infective
larvae.
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