III - Antibacterial Agents Flashcards
What are the four classes of antibacterial agents based on mechanism of action?
- Cell wall synthesis inhibitors
- Protein synthesis inhibitors
- Antimetabolites
- Nucleic acid synthesis inhibitors
List the cell wall synthesis inhibitors (4 broad categories)
Penicillins
Cephalosporins
Other beta lactams
Glycopeptides
What are the five families of penicillins?
- Natural penicillins
- Aminopenicillins
- Anti-staph penicillins
- Anti-pseudomonal penicillins
- Beta lactamase inhibitor combinations
2 natural penicillins
Penicillin V
Penicillin G
2 aminopenicillins
Amoxicillin
Ampicillin
4 anti-staph penicillins
Methicillin
Cloxacillin
Dicloxacillin
Oxacillin
3 anti-pseudomonal penicillins
Ticarcillin
Piperacillin
Carbenicillin
1 beta lactamase inhibitor combination
Amoxicillin clavulanate
How are cephalosporins categorized?
1st, 2nd, 3rd generation
List 4 1st generation cephalosporin drugs
Cefadroxil
Cephalothin
Cephalexin
Cefazolin
List two second generation cephalosporin drugs
Cefaclor
Cefoxitin
List four 3rd generation cephalosporins
Ceftiofur
Cefpodoxime
Cefovecin
Ceftriaxone
Name one beta lactam
Imipenem-cilastatin
One example of a glycopeptide
vancomycin
Five categories of protein synthesis inhibitors
- Tetracyclines
- Aminoglycosides
- Amphenicols
- Macrolides
- Lincosamides
Name three tetracyclines
Tetracycline
Oxytetracycline
Doxycycline
Name four aminoglycosides
Gentamicin
Amikacin
Tobramycin (ophthalmic)
Neomycin (topical)
Name three amphenicols
Chloramphenicol
Florfenicol
Thiamphenicol
Name five macrolides
Erythromycin
Tilmicosin
Azithromycin
Tylosin
Tulathromycin
Name two Lincosamides
Lincomycin
Clindamycin
Three categories of Antimetabolites (inhibitors of intermediate metabolism)
- Sulfonamides
- Folate reduction inhibitors
- Potentiates sulfonamides
Name two sulfonamides
Sulfadiazine
Sulfasalazine
Name three folate reduction inhibitors
Trimethoprim
Ormetoprim
Pyrimethamine
Name two Potentiates sulfonamides
Trimethoprim-sulfa
Ormetoprim-sulfadimethoxine
List the Nucleic Acid Synthesis Inhibitors
- Fluoroquinolones
- Rifampin
- Metronidazole
Name seven Fluoroquinolones
Enroflaxin
Orbifloxacin
Difloxacin
Barbofloxacin
Danofloxacin
Ciprofloxacin
Pradofloxacin
All beta lactams are considered _____.
Bactericidal
Beta lactams bind the ________ enzymes.
Bacterial transpeptidase
Aka penicillin binding proteins
This drug binds precursors of peptidoglycans interfering with bacterial cell wall synthesis.
Vancomycin
Beta lactams - what are the two most important mechanisms of resistance to penicillins?
- Enzymatic destruction by beta-lactamases produced by bacteria (cephalosporin lactam ring is more resistant)
- Altered target (altered penicillin binding protein)
________ and _________ are NOT effective against Pseudomonas and Styaphylococcus.
Natural penicillins - penicillin V and G
Amino penicillins - amoxicillin, ampicillin
(Susceptible to beta lactamase)
Spectrum of Activity: Penicillins
Gram + aerobic
Natural P
Aminopenicillins
Antipseudomonal
Spectrum of Activity: Penicillins
Gram - aerobic
Natural P (limited)
Aminopenicillins (better than NP)
Antipseudomonal
Spectrum of Activity: Penicillins
Gram + anaerobic
Natural P
Aminopenicillins (slightly less than NP)
Antipseudomonal
Spectrum of Activity: Penicillins
Gram - anaerobic
Natural P (limited effect)
Aminopenicillins (slightly less than NP)
Antipseudomonal
Spectrum of activity: cephalosporins
Gram + aerobic
1G - cefadroxil, cephalothin, cephalexin, cefazolin
2G (weak) - cefactor, cefotoxin, cefotetan
3G - ceftiofur, cefpodoxime, cefovecin, ceftazidime, cefotaxime extended gram negative (Antipseudomonal)
Spectrum of Activity: Cephalosporins
Gram -
1G - (fair)
2G - greater than 1G
3G - slightly increased resistance to beta lactamases
3G - Antipseudomonal
Spectrum of activity: cephalosporins
Gram + and - anaerobes
2nd generation - just these two
Cefoxitin
Cefotetan
Spectrum of activity: other beta lactams
Aerobic, gram +/-
Imipenem
Vancomycin
Spectrum of activity: other beta lactams
Anaerobic gram +/-
Imipenem
These two drugs are often reserved for very resistant organisms in human patients, so veterinary use should be limited.
Vancomycin
Imipenem
Imipenem-cilastatin-bactericidal
?????
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Beta lactams, in general, are very safe, but the most common adverse reaction is ____________.
Hypersensitivity - which can be life threatening
Some of the cephalosporins have been associated with _________ (very rare).
Renal failure
Any antibiotic can potentially alter ________, resulting in ____.
Normal flora of the GI tract
Resulting in diarrhea
Any drug can potentially irritate the ___, causing ___.
Stomach and small intestine
Vomiting / inappetence
Procaine penicillin G can cause a _______ reaction for up to _____ after injection.
Positive procaine test
Two weeks
The glycopeptide vancomycin is only available in ____ form.
Injectable / IV
Rapid IV administration of Vancomycin causes ______.
A hypersensitivity type reaction (histamine release)
Vancomycin has occasionally been associated with what four types of toxicity?
Renal toxicity
Ototoxicity
Reversible thrombocytopenia and neutropenia
Is vancomycin approved for use in food animals?
NO - it is prohibited.
Sodium and potassium salts of penicillin are commonly used in ____ but have to be administered ___ /day.
Foals
4x/day
Procaine penicillin G is commonly used in:
Horses and cattle
Indications for benzathine penicillin G
Shipping fever complex:
Strep, Staph aureus, Arcanobacterium pyogenes
Blackleg:
Clostridium chauvoei
Anti Staph penicillins are commonly used to treat:
Mastitis in dairy cattle
How are antipseudomonal penicillins used?
Ticarcillin IV to treat serious gram - infections in dogs
Intrauterine in mares
Amino-penicillins are used to treat:
Horses (IV ONLY)
Cattle (intramammary amoxicillin)
Dogs
Cats
The most commonly used first generation cephalosporins (2)
Cefadroxil
Cephalexin
Oral bioavailability in horses for these two cephalosporin drugs is very low.
Cefadroxil and cephalexin - first generation
This first generation cephalosporin is formulated for dairy cattle.
Cephapirin
This first generation cephalosporin is used in dogs, cats, and horses, especially with orthopedic surgeries.
Cefazolin - penetrates bone; used prophylactically
These two second generation cephalosporins are used for abdominal surgical prophylaxis in dogs and cats.
Cefoxitin
Cefotetan
Because of their activity against gram- and some anaerobic organisms.
Ceftiofur, a third generation cephalosporin is labeled for treating:
UTI in cats and dogs (SQ)
Respiratory infections in horses, cattle, and pigs
Cefovecin (Convenia) is a ___ generation cephalosporin used to treat:
3rd
Skin infections in dogs and cats
One-time injectable
This 3rd generation cephalosporin is administered daily to treat skin infections in dogs.
Cefpodoxime
These 3rd generation cephalosporins are not labeled for use in veterinary medicine but are occasionally used in dogs, cats, and foals for severe, resistant infections.
Carbapenems
Vancomycin is not labeled for use in veterinary medicine, and is illegal to use in food animals, but is occasionally used for:
Resistant Staphylococcal (MRSA) and/or Enterococcus infections in dogs, cats, and horses.
What are the five categories of protein synthesis inhibitors?
Tetracyclines
Aminoglycosides
Amphenicols
Macrolides
Lincosamides
Which protein synthesis inhibitors are bacteriostatic?
Tetracyclines
Amphenicols
Macrolides
Lincosamides
Which protein synthesis inhibitors are bacteriocidal?
Aminoglycosides
Name three tetracyclines
Tetracycline
Oxytetracycline
Doxycycline
Name four aminoglycosides.
Gentamicin
Amikacin
Tobramycin (ophthalmic)
Neomycin (topical)
Name three amphenicols
chloramphenicol
Florfenicol
Thiamphenicol
Name five macrolides
Erythromycin
Tilmicosin
Azithromycin
Tylosin
Tulathromycin
Name two Lincosamides
Lincomycin
Clindamycin
Resistance to Lincosamides, macrolides, and amphenicols
Inactivation/degradation by bacterial enzymes
Resistance to tetracyclines
EFFLEX PUMP that transports the drug out of the bacterial cell; drug fails to reach its target; plasma encoded
Resistance to one tetracycline produces cross resistance to others.
Resistance to aminoglycosides
Inactivation/degradation by bacterial enzymes
Failure to reach target because of decreased porin size occurs in some gram - organisms.
These protein synthesis inhibitors are active against rickettsiaceae, mycoplasma anaplasmataceae, and chlamydia
Tetracyclines and amphenicols
Staph, Pseudomonas and E. Coli should be considered resistant to which protein synthesis inhibitors until proven otherwise?
Tetracyclines
GI side effects of protein synthesis inhibitor tetracycline
Anorexia
Vomiting
Diarrhea
In horses, IV administration of this tetracycline can be fatal.
Doxycycline
Permanent brown discoloration of teeth can occur if this protein synthesis inhibitor is administered during tooth development.
Tetracyclines
Rapid IV administration of _____ in many species has resulted in collapse possibly due to calcium chelation.
Tetracyclines
In addition to GI side effects, tetracycline can cause these four issues.
Drug-induced fever
Renal toxicity
Hepatotoxicity
Allergic reactions
Cats are particularly prone to _______ caused by tetracyclines. Any dose should be followed by water.
Esophageal lesions (fibrosis and stricture)
Aminoglycosides have three main adverse effects:
Nephrotoxicity
Ototoxicity
Neuromuscular blockade
_____ concentrations are 50X greater in renal tissue than in plasma.
Aminoglycoside
Three ways to decrease nephrotoxicity with aminoglycosides.
- Use least toxic - Amikacin
- Do not use in hypovolemic patients
- Avoid concurrent use of other nephrotoxic drugs (furosemide, NSAIDs)
Aminoglycoside Ototoxicity is ____.
irreversible
Aminoglycoside Ototoxicity can occur with ____ administration.
Topical or systemic
Optic administration of aminoglycosides should be avoided in patients with __.
A ruptured tympanic membrane
Auditory toxicity with aminoglycosides is more common in ___ and vestibular toxicity is more common in ___.
Auditory - dogs
Vestibular - cats
Aminoglycoside toxicity induced neuromuscular blockade is __.
Reversible
Aminoglycosides can cause ___ in humans.
Irreversible aplastic anemia
Aminoglycosides can cause reversible ___ in dogs and cats.
Bone marrow suppression
Chloramphenicol inhibits ____ so can be involved in drug interactions.
CYP450 enzymes
____ was developed for use in food animals and has advantages over chloramphenicol.
Florfenicol
Name two advantages of florfenicol over chloramphenicol.
Florfenicol is not associated with aplastic anemia in people, so is not prohibited in food animals.
Florfenicol does not inhibit CYP450 enzymes
Which aminoglycoside can cause severe diarrhea in horses?
Florfenicol
This macrolide frequently causes GI upset and vomiting thought to result from its interaction with the motilin receptor which stimulates GI motility.
Erythromycin
Newer macrolides do not have this effect
Macrolides can cause __ in adult horses and __ in foals.
Severe colitis in adult horses
Hyperthermia in foals
This macrolide can cause severe cardiovascular toxicity at high doses in cattle, and even at low doses can be fatal in swine, horses, goats, and people.
Tilmicosin
Other macrolides do not share this adverse effect
Does Micotil 300, an injectable Tilmicosin drug, have an antidote?
No
In horses, ___ are generally not used because they can cause an overgrowth of Clostridium difficile resulting in severe pseudomembranous colitis.
Lincosamides
The most commonly used tetracycline in large animal veterinary medicine is ___.
Oxytetracycline
Oxytetracycline has been used for treating bovine ____, ___, and ____.
Bovine respiratory diseases
Mastitis
Anaplasmosis
Intrauterine infusion of ____ is used for cows with retained fetal membranes (off label).
Oxytetracycline
In horses, oxytetracycline has been used to treat ____.
Neorickettsia risticii (Potomac Horse Fever)
What is the most commonly used tetracycline in small animal veterinary medicine?
Doxycycline
Is doxycycline a good choice for UTIs?
No - unlike other tetracyclines, doxycycline does not achieve high concentrations in urine
Doxycycline is ____ and penetrates tissues well.
Lipophilic
This protein synthesis inhibitor is considered the drug of choice for treating intracellular pathogens such as Ehrlichiosis, Rickettsia, and Mycoplasma.
Doxycycline
Doxycycline is considered the drug of choice for treating intracellular pathogens such as ___, ___, and ____.
Ehrlichiosis
Rickettsia
Mycoplasma
What are the three most commonly used aminoglycosides in veterinary medicine?
Gentamicin
Amikacin
Neomycin
Three differences between the aminoglycosides gentamicin and Amikacin.
- Amikacin is less susceptible to bacterial inactivation than gentamicin.
- Amikacin is potentially less likely to produce nephrotoxicity.
- Amikacin is more expensive than gentamicin.
Which aminoglycoside (protein synthesis inhibitor) is frequently used systemically in horses?
Gentamicin
Which aminoglycoside (protein synthesis inhibitor) is used in foals, dogs, and cats.
Amikacin
Which aminoglycoside (protein synthesis inhibitor) is used as an intrauterine infusion for horses?
Amikacin
Which aminoglycoside (protein synthesis inhibitor) is used for regional limb perfusion to treat lower limb bone and joint infections?
Gentamicin
Which protein synthesis inhibitors are lipid soluble?
Amphenicols
The amphenicols (protein synthesis inhibitors) are lipid soluble and therefore achieve high concentrations within ___ and can gain access to tissues such as ___.
Cells
CNS, prostate
Chloramphenicol is used in small animals primarily for ___, some ___, and ___.
CNS infections
Some rickettsiae
Mycoplasma
This protein synthesis inhibitor is sometimes used in horses (has reasonable oral bioavailability and does not cause serious adverse effects on the GI flora) but is ILLEGAL for use in food animals.
Chloramphenicol
____ is approved for use as an injectable (IM or SQ) for treating bovine respiratory disease and bovine interdigital phlegmon (foot rot).
Florfenicol
Florfenicol (protein synthesis inhibitor) is approved for use as an injectable (IM, SQ) for treating bovine ___ and bovine ___.
Bovine respiratory disease
Bovine interdigital phlegmon (foot rot)
These macrolides (protein synthesis inhibitors) are the three most commonly used in small animals and horses.
Erythromycin
Azithromycin
Clarithromycin
Because of its long tissue half-life in the respiratory tract, this protein synthesis inhibitor has an unusual dosing recommendation - once every three days or once a day for three days then stop.
Azithromycin (a macrolide)
Macrolides (protein synthesis inhibitors), particularly ____, are lipid soluble, and are therefore useful against susceptible ___.
Azithromycin
Intracellular bacteria
In horses, both ___ and ____ are effective for treating Rhodococcus equi infections.
Clarithromycin
Azithromycin
Which two macrolides are used in dogs and cats to treat a variety of respiratory infections?
Clarithromycin
Azithromycin
Also effective for treating Rhodococcus equi infections in horses
Macrolides are ____ inhibitors.
Protein synthesis
____ are approved for use as an injectable (IM/SQ) for treating bovine respiratory disease and bovine interdigital phlegmon (foot rot).
Macrolides (protein synthesis inhibitors)
- Gamithromycin
- Tulathromycin
- Tilmicosin
This macrolide may have direct or indirect immunologic properties and may reduce antigenic stimulation in treating dogs with IBD.
Tylosin
(Macrolide / Protein Synthesis Inhibitor)
T/F
Considering the role of altered antigens in chronic IBD, favorable experiences, minimal adverse effects, and low cost of the drug, Tylosin remains an option for treatment of canine IBD.
True
This drug is by far the most commonly used lincosamide (protein synthesis inhibitor).
Clindamycin
In small animals clindamycin is used to treat these four conditions.
Wounds
Abscesses
Periodontal disease
Osteomyelitis
Lincosamides are ___ inhibitors.
Protein synthesis
What are the two categories of Antimetabolites (inhibitors of intermediate metabolism)?
PABA analogs
Folate reduction inhibitors
Name three PABA analogs (Antimetabolites)
Sulfadimetoxine
Sulfadiazine
Sulfametoxazole
Name two folate reduction inhibitors (Antimetabolites).
Ormetoprim
Trimethoprim
The combination of a sulfonamide with a folate reduction inhibitor is ___.
Synergistic and bacteriocidal
There are numerous mechanisms of resistance to the Antimetabolites; the most important plasmid-mediated form of resistance is ___, which has limited the clinical utility of these drugs in many clinical situations.
Impaired penetration
Are Antimetabolites useful in treating anaerobes?
NO
Potentiated _____ are NOT good choices for Staph, Enterococcus, E. Coli, Proteus, Klebsiella, Psuedomonas, and many anaerobes.
Sulfonamides
Sulfonamides are inhibitors of ____.
Intermediate metabolism
The most important adverse effect of sulfonamides is a ___ which occurs in people too.
Hypersensitivity reaction
If a decrease in tear production is noted, these drugs should be discontinued, with normal tear production expected to resume.
Sulfonamides (Antimetabolites)
_____ can cause immune-mediated diseases ranging from mild to severe and affect skin, liver, kidney, hematopoietic system, and eyes.
Sulfonamides (Antimetabolites)
Sulfonamides can cause ____ - decreased tear production by the lacrimal glands - and it is recommended that the patient be monitored during treatment with ___.
Keratoconjunctivitis sicca (KCS)
Schirmer tear tests
Rarely, ____ associated with sulfonamide crystalluria has been reported.
Nephrotoxicity
Sulfonamides are metabolized by ___. Because dogs lack this metabolic pathway, they are less likely to develop nephrotoxicity associated with ____ than other species.
Acetylation
Sulfonamide crystalluria
Sulfonamides and potentiated sulfonamides are available in a variety of formulations (oral, injectable, feed additives) with indications including the treatment of which of the below?
- intestinal infections
- infections in CNS, joints
- bacterial enteritis
- bacterial pneumonia
- skin and soft tissue infections in dogs and cats
- cystitis and prostate in dogs
All of the above
Name the four most common sulfonamides used in veterinary medicine.
Sulfadimethoxine
Sulfadimethoxine + Ormetoprim
Sulfadiazine + trimethoprim
Sulfamethoxazole + trimethoprim
_______ have caused the most tissue residue violations in the U.S. with the greatest problems coming from pork, veal, and poultry.
Sulfonamides
This sulfonamide (antimetabolite) is labeled for use in many species.
Sulfadimethoxine
This sulfonamide (antimetabolite) is labeled for use in dogs.
Sulfadimethoxine + Ormetoprim
This sulfonamide (antimetabolite) is labeled for use in horses - availability for dogs and cats has declined.
Sulfadiazine + trimethoprim
This sulfonamide (antimetabolite) is most commonly a human formulation but is used off-label in dogs, cats, and horses.
Sulfamethoxazole + trimethoprim
Nucleic acid synthesis inhibitors include __, ___, and ___.
Fluoroquinolones
Rifampin
Metronidazole
Name seven Fluoroquinolones
Enrofloxacin
Orbifloxacin
Difloxacin
Marbofloxacin
Danofloxacin
Ciprofloxacin
Pradofloxacin
Enro-Orbi-Di-Margo-Dano-Cipro-Prado
What is the MOA of Fluoroquinolones (Nucleic acid inhibitors)?
Inhibit bacterial DNA gyrase (topoisomerase II) and topoisomerase IV enzyme which are necessary for transcription, translation, and bacterial replication.
Are Fluoroquinolones bacteriostatic or bacteriocidal?
Bacteriocidal
Fluoroquinolones inhibit ____.
Nucleic acid synthesis
What is the MOA of rifampin?
Inhibits DNA-dependent RNA polymerase interfering with RNA synthesis
Bacteriocidal
Is rifampin bacteriostatic or bacteriocidal?
Bacteriocidal at high concentrations
What is the MOA of metronidazole?
Impairs microbial RNA and DNA synthesis by an undefined mechanism.
Is metronidazole bacteriostatic or bacteriocidal?
Bacteriocidal
Fluoroquinolone (Nucleic acid inhibitor) mechanism of resistance
Alteration of target - decreased porin size by gram negative bacteria results in failure of drug to reach its target
Rifampin (Nucleic acid synthesis inhibitor) mechanism of resistance
Alteration of drug target; if used as a sole agent, resistance often develops rapidly, limiting the usefulness of this drug
Metronidazole (Nucleic acid synthesis inhibitor) mechanism of resistance
Unknown
Fluoroquinolones (Nucleic acid inhibitors) are ineffective against ____.
Anaerobes
___ is a “next generation” fluoroquinolone FDA approved for cats only and has greater gram positive anaerobe activity while maintaining gram negative activity.
Pradofloxacin
Metronidazole is effective against gram positive and gram negative ___.
Anaerobes
Metronidazole is a __ inhibitor.
Nucleic acid synthesis
___ are effective in treating gram positive and gram negative aerobes.
Fluoroquinolones
Rifampin is effective against gram ____ _____.
Gram positive aerobes
Fluoroquinolones (Nucleic acid synthesis inhibitors) can cause irreversible _____.
Cartilage damage in growing animals
____ should not be used in growing animals.
Fluoroquinolones
This Nucleic acid synthesis inhibitor can cause retinopathy in cats resulting in irreversible blindness.
Fluoroquinolones
Tends to be related to higher doses, or use in cats with compromised renal function
At high plasma concentrations such as those achieved after IV injection or extremely high oral doses, ___ can be induced by Fluoroquinolones.
Seizures
Rifampin can cause ____ toxicity and a _____.
Liver toxicity
Red-orange discoloration of urine
Rifampin ___ drug metabolizing enzymes.
Induces
*drug interactions are a concern
Are drug interactions a concern with rifampin?
Yes - it induces drug metabolizing enzymes
Metronidazole can cause dose-dependent ___.
Vestibular toxicity
Generally slowly reversible
Metronidazole caused ___ in two cats.
Neurotoxicosis
Three Fluoroquinolones (Nucleic acid synthesis inhibitors) are FDA approved for use in dogs and cats:
Enrofloxacin
Marbofloxacin
Orbifloxacin
One fluoroquinolone (Nucleic acid synthesis inhibitor) is labeled only for use in dogs:
Difloxacin
One fluoroquinolone (Nucleic acid synthesis inhibitor) is labeled only for use in cats:
Pradofloxacin
_____ have a lower incidence of side effects than aminoglycosides.
Fluoroquinolones
Fluoroquinolones are ___ and achieve high intracellular concentrations and penetrate tissues including prostate, respiratory tract and CNS.
Lipid soluble
All veterinary labeled Fluoroquinolones achieve high concentrations in urine (and are therefore good choices in treating resistant UTIs) except:
Difloxacin
Which Fluoroquinolones (Nucleic acid synthesis inhibitors) are approved for use in horses?
None, but Enrofloxacin, Orbifloxacin, and Marbofloxacin have been used orally and by injection.
In cattle, which two Fluoroquinolones are approved for treating respiratory disease?
Enrofloxacin
Danofloxacin
Is ELDU of Fluoroquinolones in food animals legal?
NO
Why are Fluoroquinolones that were once approved for use in poultry pulled from the market in the US?
Because of the potential for causing spread of resistant Campylobacter
Fluoroquinolones are ____ after oral administration, although __ do occur.
Well absorbed
Drug interactions
Fluoroquinolones ______ CYP450 drug metabolizing enzymes.
Inhibit
Can cause an increase in plasma concentrations of some drugs if administered concurrently
Divalent (magnesium and calcium) and trivalent (aluminum) cations significantly ___________ and can lead to therapeutic failure of Fluoroquinolones.
Decrease oral bioavailability
Pradofloxacin has been shown to cause ____ in dogs, potentially resulting in severe thrombocytopenia and neutropenia.
Bone marrow suppression
Which fluoroquinolone has been shown to cause bone marrow suppression in dogs?
Pradofloxacin
In veterinary medicine, rifampin is used mainly in combination with ___ for treating ____.
Macrolides
Rhodococcus equi pneumonia in foals
Are there FDA approved veterinary formulations for metronidazole?
NO
This Nucleic acid synthesis inhibitor is used primarily to treat anaerobic infections in dogs and horses.
Metronidazole
Is it legal to use metronidazole (a Nucleic acid synthesis inhibitor) in food animals?
NO
Is metronidazole (a Nucleic acid synthesis inhibitor) convenient for dosing cats?
NO
Metronidazole is highly _____ therefore distributes well to the CNS and into abscesses.
Lipid soluble
MOA of polymixin B
Decomposes in acidic environments to release formaldehyde; Formaldehyde acts as a urinary antiseptic
This drug has been used for long-term maintenance of refractive UTIs in dogs.
Polymyxin B/Methenamine
_________ is well absorbed after oral administration and is excreted unchanged in the urine. Acidic urine results in the release of formaldehyde.
Methenamine/Polymyxin B
The Polymyxins are water soluble products of ___. They are basic, cyclic decapeptides.
Bacillus Polymyxa
T/F:
Polymyxin B also comes in many topical preparations - otic, ocular, ophthalmic.
True
Polymyxin B is used at low, carefully controlled doses to bind ____.
Endotoxin
_____ may develop resistance to polymyxin B through altered permeability.
Pseudomonas
MOA Polymyxin B (endotoxins)
Detergent-like action disrupts gram negative cell membranes
Cationic polymyxins interact with an ionic phospholipids (endotoxin) in the gram negative cell wall, disrupting cell wall integrity
________ is an indication for using low, carefully controlled doses of polymyxin b to bind endotoxins.
Equine colic
Oral bioavailability of polymyxins is ___.
Very poor
The polymyxins display ___ in the body, where binding to mammalian cell membranes contributes to significant accumulation during lung therapeutic regiments.
Poor distribution
Elimination of polymyxin B is via:
Glomerular filtration of the parent compound
Parenteral administration of polymyxin may lead to:
Nephrotoxicity
Neuromuscular blockade
CNS toxicity
Polymyxin toxicities appear to be ____.
Dose dependent
Treatment with a polymyxin requires strict adherence to dose guidelines
Drugs to consider with MRSA infection if a susceptibility test can confirm activity.
Chloramphenicol
Tetracycline (doxycycline, minocycline)
Aminoglycosides (gentamicin, Amikacin)
Rifampin
Treatment of Pseudomonas
Amikacin and gentamycin
2nd/3rd generation cephalosporins (ceftazidime, cefotaxime)
Anti-pseudomonas penicillins (Ticarcillin, piperacillin, carbenicillin, piperacillin-tazobactam)
Imipenem (IV)
Fluoroquinolone + a beta-lactam
Tx Nocardia
Potentiated sulfonamides
Tx mycoplasma
Tetracyclines
Macrolides
Amphenicols
Tx rickettsiaceae and anaplasmataceae
Tetracyclines
Amphenicols
Tx Gram positive anaerobes
Pradofloxacin (cat)
Metronidazole (no cat)
Aminopenicillins
Newer macrolides
Clindamycin
Natural penicillins
Tetracyclines
Tx gram negative anaerobes
Pradofloxacin (cat)
Metronidazole (no cat)
Aminopenicillins
Newer macrolides
Amphenicols
Tx gram positive and negative anaerobes
Pradofloxacin (cat)
Metronidazole (no cat)
Aminopenicillins
Newer macrolides
Treatment only gram positive anaerobes
Clindamycin
Natural penicillins
Tetracyclines
Treatment only gram negative anaerobes
Amphenicols