1
Q
Antimicrobials
A
Have the ability to kill or suppress the multiplication or growth of microorganisms
2
Q
Bacteriocidal
A
Antimicrobial that kills microbes
3
Q
Bacteriostatic
A
Antimicrobial that inhibits growth or replication of microbes
4
Q
What are the goals of Antimicrobials?
A
- Kill / Disable pathogen without killing the host (patient)
-Microbe must be susceptible to the antimicrobial - Must reach the site of infection and at high enough concentrations to kill or inhibit the microorganism
- Patient must tolerate concentrations necessary to achieve therapeutic range
- Patient’s immune system must be competent (Especially when using STATIC medications)
5
Q
Antimicrobial Mechanisms of Action
A
- Inhibition of cell wall synthesis (cidal by inhibition of enzymes for cell wall synthesis)
- Alteration in cell membrane permeability (static or cidal due to loss of cellular substances/cell lysis)
- Inhibition of protein synthesis (static or cidal due to interference with protein synthesis)
- Interference with metabolism (static due to lack of essential materials for bacterial metabolism)
- Nucleic acid impairment (cidal due to nucleic acid enzyme inhibition)
6
Q
Spectrum
A
range of bacteria on which an antibiotic is effective
(Gram +,Gram –, Aerobic, Anaerobic)
7
Q
What is the function of sensitivity testing?
A
Identify antibiotic effectiveness
8
Q
Zone of Inhibition
A
Determines the ability of the drug to prevent growth (Sensitive, Intermediate, Resistant)
The zone sizes are looked up on a standardized
chart to give a result of sensitive, intermediate or resistant
Many charts have a corresponding column that also gives the MIC for that drug
9
Q
MIC
A
(Minimum Inhibitory Concentration)
- MIC represents the lowest concentration of drug at which growth of the bacterium is inhibited
- It is a measurement of susceptibility of a bacterial strain to the effects of an antimicrobial agent
10
Q
What are the antibiotics that target the cell wall?
A
Penicillins, Cephalosporins, Bacitracin, Vancomycin
11
Q
What drug am I?
- Cidal group derived from a mold (natural)
- Mainly semi-synthetic today
- Contain a beta–lactam ring in their structure that interferes with cell wall synthesis
- Recognized by having the suffix “cillin” in the generic drug name
- Rapidly distributed to most tissues
A
Penicillins
12
Q
What are the features of Penicillins?
A
- The first penicillins were narrow spectrum with activity against mostly Gram(+) bacteria
- Pen G was one of the first developed but must be used by parenteral routes due to inactivation by stomach acid and is commonly in a suspension
- Pen G is also available as a Na+ or K+ salts that can be given IV and is also well absorbed IM
- Pen V then became available in oral tablets due to better absorption from the GI tract and is also available in Na+/K+ injectable salts
13
Q
What is important about Penicillin G suspensions?
A
- Procaine and Benzathine molecules are added to IM suspensions to delay absorption and increase duration of action
- Pen G suspensions should never be given IV!!!
14
Q
How are Broad spectrum penicillins different? (name some examples of these penicillins)
A
- Semisynthetics that have greater activity against Gram(–) bacteria
- Includes amoxicillin, ampicillin,carbenicillin, ticarcillin, and methicillin
- Food affects the bioavailabilty of oral penicillins, so they should be given 1-2 hrs before eating
- Amoxicillin may be given with food
15
Q
Resistance Factors of Penicillins
A
- Due to the penicillinase/beta-lactamase I enzyme found in some bacteria that destroys the beta-lactam ring and renders the antibiotic less effective
- oxacillin, dicloxacillin, cloxacillin, floxacillin and methicillin have a narrower spectrum but are “penicillinase resistant” and used mainly for treatment of skin, osteomyeleitis, and mastitis infusions
16
Q
How are Potentiated Penicillins different? (and an example of this drug)
A
- A “potentiated” drug has an additional chemical(s) added to enhance the effects of both drugs
- Clavulanic acid binds to beta-lactamase
- When added to amoxicillin, the beta-lactam ring is protected against destruction by beta-lactamase producing bacteria
- Clavamox® is the amoxicillin/clavulanic acid combination used in animals (Augmentin® human product)
17
Q
What are the adverse effects of Penicillins?
A
- One of the safest antibiotics, but may see anorexia, vomiting and diarrhea (v/d) when given orally
- Severe allergic reactions, even anaphylaxis may occur, especially when given IV
- GI superinfections from death of gut lactobacilli (beneficial bacteria) resulting in diarrhea, dehydration, and possibly death are prevalent in guinea pigs, rabbits, and hamsters with oral administration of penicillins
- May use Ben-e-bac lactobacillus supplement to off set superinfections
18
Q
What drug am I?
- Cidal, broad sectrum, semisythetic group derived from cepalosporin C
- Structurally and chemically similar to penicillin
- Contain a beta-lactam ring in their structure
- Recognized by most having the prefix “ceph” or “cef” in their generic or trade names
A
Cephalosporins
19
Q
What are the features of Cephalosporins?
A
- Classified into four “generations”
- Well distributed to most tissues
- First generation are well absorbed by the GI whereas third and fourth generations are usually injectable
- Used frequently when penicillin is not effective
- cephalexin (Keflex®) is a commonly used injectable
20
Q
What are the differences between the generations of Penicillins?
A
- First-generation is most commonly used in veterinary medicine and spectrum is mostly Gram(+) and some Gram(-)
- Second-generation has broader spectrum against Gram(–) and slightly less Gram(+) than first generation
- Third-generation have even broader Gram – spectrum of activity and are beta-lactamase II (cepalosporinase) resistant
- Fourth-generation like the third with activity against Pseudomonas aerugnosa and some Enterobacteriaceae (Gram(-) GI rods)
21
Q
What are the adverse effects of Cephalosporins?
A
- Similar to penicillin, so animals allergic to penicllin may also be allergic to cephalosporins
- Hypersensitivity reactions can cause fever and rashes
- Superinfection and GI signs (more common in cats) may occur (v/d, anorexia)
- When given orally, GI signs may be reduced by administration with a small meal IM injection can cause local pain and inflammation
- Adverse effects worsen as the generation increases
22
Q
What drug am I?
- Polypeptide that disrupts the cell wall like penicillins and cephalosporins, but has no beta-lactam ring
- Primary spectrum is Gram(+)
- Toxic to the kidneys and used mainly for topical treatment of skin, mucous membranes, and ocular surfaces
- Due to poor GI absorption, may be used a feed additive for intestinal pathogens
- Often seen in combination “triple antibiotic ointments” with neomycin and polymyxin B to create a wide spectrum topical
A
Bacitracin
23
Q
What Drug am I?
- Cidal glycopeptide used primarily for treatment of infections resistant to penicllins and cephalosporins
- Only available for IV administration
- Primary spectrum is Gram(+)
- Used mainly in humans for treatment of drug resistant Staph aureus
- Rarely used in non-humans to avoid development of resistance
- Adverse effects in animals are rare but include ototoxicity, nephrotoxicity and pain on IV injection
A
Vancomycin
24
Q
What are the antibiotics that target the cell membrane?
A
Polymyxin B
25
- Polypeptide that acts on the phospholipid bilayer of the cell membrane
- Spectrum is Gram(-) only
- Not absorbed orally and has local effect topically
- Often seen in combination “triple antibiotic ointments” with bacitracin and neomycin to create a wide-spectrum topical
*Since both bacteria and animals have cell membranes, this group can cause toxicity problems in animals*
Cell Membrane Agents
26
What are the antibiotics that target the protein synthesis agents?
Aminoglycosides, Tetracyclines, Lincosamides, Chloramphenicol, Florfenicol, Macrolids
27
What drug am I?
- A group of Cidal antibiotics dervied from Streptomyces microbes
- Work by inhibiting bacterial protein synthesis
- Spectrum mainly Gram(-)
- Most not absorbed from the GI tract so given parenterally for short term treatment of Gram(-) septicemia
- Recognized by most having “micin” or “mycin” endings in their generic names
Aminoglycosides
28
Features of Aminoglycosides
- Achieve high concentrations in the kidney and inner ear
- Inactivated by the presence of pus and cellular debris
- Synergistic with beta-lactam antibiotics but do not mix in the same syringe (inactivates other antibiotic)
- Not approved for use in food producing animals
29
Adverse Effects of Aminoglycosides
- Ototoxicity (auditory and vestibular)
- Make sure tympanic membrane is intact prior to topical use
- Nephrotoxicity (monitor kidney function, especially if dehydrated)
- Neurotoxicity (with high doses)
- Often referred to as “aminoglycoside toxic syndrome”
30
What drug am I?
- Group of Static, broad spectrum antibiotics derived from Streptomyces
- Effective against Gram(+), Gram (-) bacteria including Mycoplasma and Chlamydia
- Also used for the treatment of rickettsial organsims (e.g. Erlichia), parasitic bacteria (e.g. Mycoplasma haemofelis) and spirochetes (e.g. Borrelia burgdorferi)
- Recognized by having “cycline” in their generic names
Tetracyclines
31
What are the features of Tetracyclines?
- Available in both oral and injectable forms
- Achieves rapid distribution, including some CNS levels
- Binds to compounds that contain iron, calcium, aluminum, or magnesium
- Should not be given with iron supplements, antacids, or products for diarrhea (containing kaolin, pectin or bismuth)
- In general, should not be given with dairy products
- Resistance is common
32
What are the Adverse Effects of Tetracyclines?
- May cause renal tubular necrosis at high doses
- Can affect bone (slows development) and tooth formation (yellow discoloration) if used during pregnancy or in young animals due to calcium binding
- May cause fever in cats
- Nephrotoxic if outdated
- Injectable products are painful when given IM and may cause problems with cardiac contraction due to decreased calcium available
33
What drug am I?
- Group of Static/Cidal antibiotics derived from Streptomyces
- Two main drugs used in veterinary medicine are lincomycin (Lincocin®) for Gram(+) skin and soft tissue infections and clindamycin (Antirobe®) for anaerobes and Gram(+) infections of the skin and oral cavity, and respiratory tract infections (active against Mycoplasma)
Lincosamides
34
Adverse Effects of Lincosamides
Diarrhea/enteritis may be severe,especially in pocket pets, and if given orally to horses and ruminants
35
What drug am I?
- Static, broad spectrum antibiotic derived from Streptomyces
- Gram(+), Gram(-) and Rickettsia
- BANNED for use in FOOD producing animals in the USA due to potential for bone marrow suppression in humans
- Not used as a “first-line drug” due to toxicity
Chloramphenicol
36
What are the features of Chloramphenicol?
- Readily absorbed into tissue and able to penetrate lipid membranes and selective barriers such as CNS
- Available in oral, injectable and ointment forms
- Commonly used for exotics and pocket pets
37
Adverse effects of Chloramphenicol
- Bone marrow suppression with high doses or prolonged use, seen especially in cats
- Potent inhibitor of microsomal enzyme P450 so will increase the concentrations of other drugs, possibly causing toxicity
- GI signs (v/d, anorexia)
- Fatal aplastic anemia in humans, even at very low doses
- Wear gloves when administering to patient and use extreme caution when handling
38
What drug am I?
- Related to chloramphenicol but approved for use in cattle
- Injectable only (use neck area)
- Well distribute to tissues/therapeutic CNS levels
- Commonly used to treat bovine respiratory disease and foot rot
Florfenicol
39
What are the adverse effects of Florfenicol?
Inappetence, decreased water consumption and diarrhea
40
What drug am I?
- Group of Static/Cidal, broad spectrum antibiotics derived from Streptomyces
- Well distributed to most tissues except the CNS
- GI distress is major side effect and is route dependant (do not administer orally to rodents and rabbits)
- Diarrhea in large animals may be severe (tylosin may cause fatal diarrhea in horses)
Macrolids
41
What are the three main Macrolids used in Veterinary Med?
- erythromycin (Erythro-100®) mainly used to treat penicillin-resistant skin and respiratory infections or in animals allergic to penicillin (oral and ointment forms)
- tylosin (Tylan®) used mainly in livestock for a variety of diseases and as a feed/water additive (oral and injectable forms) and for treatment of chronic colitis given orally in dogs and cats
- tilmicosin (Micotil®) used to treat bovine respiratory disease (only approved for SQ use in cattle)
42
What are the antibiotics that target Antimetabolites?
Sulfonamides
43
What drug am I?
- Also known as the “Sulfa” drugs
- One of the first synthetic antimicrobials used widely in both humans and animals
- Classified by how well they are absorbed from the GI tract
Sulfonamides
44
What are the classifications of Sulfonamides
“enteric” sulfas are poorly absorbed from the intestine and act locally on intestinal pathogens
“systemic” sulfas are well absorbed from the intestine
45
What are the features of Sulfonamides?
- Broad spectrum and also treat toxoplasma and coccidia protozoans
- Bacteriostatic by interfering with folic acid synthesis needed for bacterial metabolism
- Due to the widespread use of sulfa drugs, resistance to many microorganisms developed
- Resistance is much less common when sulfas are potentiated with ormetoprim or trimethoprim
- Potentiated sulfas are overall more effective since separately the sulfa and the potentiator are “static” but together they become “cidal”
46
What are the adverse effects of Sulfonamides?
- Crystal formation in the renal tubules can cause kidney damage
- Hypersensitivity/ severe allergic reactions can occur (seen more in Dobermans)
- Skin reactions (pruritis, rashes, facial swelling)
- Fever, hepatitis, arthritis
- Increased salivation in cats
- KCS (may be irreversible)
- Blood imbalances (leukopenia, thrombocytopenia, hemolytic anemia)
47
What are the antibiotics that target Nucleic Acids?
Quinolones/Fluoroquinolones
48
What are the features of Quinolones/Fluroquinolones?
- Well absorbed into tissues with high availability
- Crosses selective barriers
- Used in most exotic animal species because of its safety and activity against many pathogens
- Available in many formulations including injectable/oral and otic solution
49
What are the Adverse Effects of Quinolones/Fluroquinolones?
- Occasional v/d at high doses
- Erosions of developing cartilage (articular cartilage) in young animals, with large breed, rapidly growing dogs being most sensitive (between 4 and 28 weeks of age)
- Dose-related permanent blindness in cats has been reported
-High concentrations may cause CNS toxicity, especially in animals with renal failure
50
Metronidazole
- Nitroimidazole related to the antifungal medications
- Cidal anitbacterial and antiprotozoal activity thought to work by disrupting DNA synthesis
- Well absorbed when given orally
- No approved veterinary form but is commonly used for Giardia and anaerobes
- Drug of choice for canine diarrhea
- Also used to treat inflammatory bowel disease
Adverse Effects:
Anorexia, v/d, bitter taste
Neurologic signs such as ataxia, tremors, and seizures, especially in cats at high doses (discontinue immediately)
Use cautiously during pregnancy due to possible teratogenicity
51
rifampin
Cidal/Static, broad spectrum antibiotic that works by disrupting RNA synthesis
Relatively well absorbed from the GI tract
Used in combination with erythromycin or azithromycin for the treatment of Rhodococcus equi pneumonia foals
Causes reddish discoloration to urine, tears, sweat and saliva
Warn clients of this!
52
nitrofurans
Cidal, broad spectrum antibiotics that work by inhibiting bacterial enzyme synthesis
Family members include nitrofurazone (Furazone®), nitrofurantoin (Macrodantin®), and furazolidone (Topazon®)
nitrofurantoin is rapidly eliminated and used to treat urinary tract infections because it is filtered unchanged by the kidney
furazolidone and nitrofurazone are used mainly topically for wounds and ocular infections
Adverse Effects:
nitrofuran use is prohibited in food producing animals due to carcinogenic residues, however it may be used topically
Systemic use may cause GI and liver disturbances
53
Polyene Antifungals
- Poorly absorbed from the GI tract and fairly toxic when given IV systemically
- Work by binding to ergosterol in the fungal cell membrane
- Members include amphotericin B (Fungizone®) and nystatin (found in Panalog® and other combination topical antimicrobial ointments)
54
nystatin
Given orally for Candida albicans overgrowth in the GI tract secondary to antibiotic therapy
Found in various topical ointments
Oral preparations for local infections of the mouth
IV injection (toxicity)
55
amphotericin B
Used IV to treat severe systemic mycotic infections
Does not penetrate many tissues well, but has a long duration of action in the tissues it can penetrate (dosed EOD or three times per week)
Light /moisture sensitive
Administered through dilution in 5% dextrose solution
Used cautiously due to nephrotoxicity and renal function should be monitored
56
Imidazoles
Work by causing leakage of the fungal cell membrane
Less toxic than Polyenes but have delayed onset of action
Most commonly used are ketoconazole (Nizoral®) and miconazole (Monistat®, Conofite®)
ketoconazole is available in oral and topical forms
miconazole comes in parenteral and topical forms
Both treat systemic and some superficial fungal infections
Adverse effects of hepatotoxicity and cardiotoxicity have been noted
57
Ketoconazole
type of imidazole, oral and topical forms
58
griseofulvin
- Available only as an oral preparation to treat dermatophyte infections of the skin, hair, and nails
- Fungistatic and works by disrupting fungal cell division
- Available in microsize and ultramicrosize forms that should be given with a fatty meal to enhance absorption
- Adverse effects include GI signs and teratogenicity (do not give to pregnant or breeding animals, especially cats)
- Anemia and leukopenia in cats (idiosyncratic or dose related?)
- Dosage regimens may be long, but should continue until fungal cultures are negative
59
interferon
is a protein substance with multiple roles in the body’s defense mechanisms
Protects host cells from viruses
Stimulates noninfected cells to produce antiviral proteins
Mainly used in veterinary medicine for treatment of FeLV and ocular herpes in cats
Adverse effects rarely seen in cats
60
L-lysine
is an amino acid supplement that works by competing with arginine, which is an essential amino acid of Feline Herpes Virus Type 1 (FHV-1)
may be effective in suppressing FHV-1 infection in cats
no adverse effects reported in cats
comes as powder to be mixed with food or as a gel for oral administration
VET - Pharm
flashcards
Decks in class (17)
# Cards
