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Pharmocology > Unit 3 antimicrobials > Flashcards

Unit 3 antimicrobials Flashcards

1
Q

Antibiotics are

A

Compounds used to kill or inhibit microbial growth

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2
Q

Types of antibiotics

A

Defined by
Target organisms (AKA their spectrum of activity)
Static inhibition (inhibition of replication- do nto directly kill) vs -cidial (kill)

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3
Q

target organisms for antibiotics

A

Bacteria
Fungi
Virus
Protozoan

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4
Q

Static drug

A

Bacteriostat
Fungastiat
Virustat
Protozoistat

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5
Q

Cilda drug

A

Bactericide
Fungicide
Virucide
Protozoicide

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6
Q

Antimicrobial therapy goal

A

Goal is to kill or inhibit specific pathogens while not harming the host

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7
Q

Factors involved in choosing an appropriate drug for antimicrobial therapy

A

Susceptible microorganism
Determined based on culture and sensitivity
Access the site of infection at appropriate concentrations
Host tolerance to the drug

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8
Q

Microbial susceptibility Based on Minimum inhibitory concentration (MIC)

A

Strain- and antimicrobial specific
Compare Maximum TOlerated Dose (MTD) to MIC
Compare the drugs therapeutic range with its MIC classifies a pathogen as sensitive or resistant to that drug

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9
Q

Microbial susceptibility is based on

A

Minimum inhibitory concentration

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10
Q

How antibacterials work:

A

Concentation-dependence:
Based on peak serum concentration maintained above MIC
Time-dependence:
Based on amount of time drug stays above the minimum inhibitory concentration (MIC)

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11
Q

Microbial Resistance: is

A

Capability of an organism to survive in the presence of antimicrobials, passed on to other microbes via:
Chromosomes–Vertical Transmission
Plasmids–Horizontal Transmission
May result from random genetic mutations or the inappropriate use of antimicrobials
This causes Selection Pressure which results in large resistant populations

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12
Q

Risk of resistance is increased when

A

antibiotics are used inappropriately:
Anytime bacteria are exposed to an ABC and not killed
Broad spectrum, bacteriostatic, under-dosing below MIC
Unnecessary prescription
Unnecessary treating:
metaphylaxis/prophylaxis
viral infections (Not all bugs need drugs!)
Poor owner compliance
Unnecessary exposure
Exposure through residues, failure to follow WDTs

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13
Q

Drug residues of antimicrobials

A

When a food-animal is treated with a medication, food products (meat, egg, milk) must not contain drug residues form the treatment
Residues are unacceptable
Human hypersensitivities
Proliferation of resistant microbial populations
Residues can be avoided

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14
Q

How can drug residues be avoided

A

Ensure withdrawal times for drugs are adhered to
Label all dispensed medications with clear instructions for proper administration and include withdrawal times

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15
Q

How to decrese microbial resistance

A

To reduce the emergence of resistant populations of bacteria the appropriate antimicrobial does must be used and the full duration of treatment must be completed
Client education is key

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16
Q

Antimicrobial stewardship

A

Some antibodies should be “off limits”- save the big guns for the big bugs! E.g. MRSA (methicillin resistant staph aureus)
Thai includes prescription feed additives
Ideally treat based on C&S

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17
Q

Mechanism of action (MOA) of antibiotics

A

Five basic mechanisms of antibiotic action against bacterial cells
Inhibition of cell wall synthesis (most common mechanism)
Inhibition of protein synthesis (translation)(second largest class)
Alteration of cell membranes
Inhibition of nucleic acid synthesis
Antimetabolite activity

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18
Q

Inhibition of cell wall synthesis

A

Bacterial protoplasm draws water into the bacteria by osmosis, the bacterial cell wall keeps the bacterium from bursting
These drugs are most effective against actively dividing bacteria

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19
Q

Inhibition of protein synthesis (translation)(second largest class)

A

Distribution of protein synthesis by combining with ribosome ind interfering with mRNA or tRNA
Blocks cell from dividing and results in cell death
Can also cause damage to cell membrane

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20
Q

Alteration of cell membrane

A

These drugs make the cell membrane “leaky”
Drug molecules can more readily enter the cell
Cytoplasmic components are more readily able to escape the cell

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21
Q

Inhibition of nucleic acid synthesis

A

Interfere with the replication and transcription of DNA in bacterial cells
These drugs are less preferred because they may also interfere with human DNA replication and transcription
Newer antibiotics
Disrupt the DNA function by interfering with the enzymes needed for DNA to function or replicate, rather than the replication itself
Attack specific types of structure only found in bacteria and not mammalian cells

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22
Q

Antimetabolite activity

A

There are antibiotics that mimic the structure of certain substrates in such a way that the normal substrate is replaced so the enzymes does not work as it should
In the process, needed metabolites are not created jeopardising the well being of the bacteria

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23
Q

The ideal antibiotic protocol

A

Organism has been identified
Organism is susceptible to drug chosen
Drug has a narrow spectrum
Drug is bactericidal
If bacteriostatic, the patient MUST have a functioning immune system
Good distribution to the site of infection
High therapeutic index; few side effects; patient must be able to tolerate treatment
No ability to acquire resistance
Dosing regimen is easy to follow
Patient returns for follow up to ensure therapeutic goal reached

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24
Q

Therapeutic goals when using antibiotics

A

Resolution of bacterial infection
Non or acceptable side effects
No resistance

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25
Q

1st line antibiotics

A

The “go to” antibiotics
Three characteristics
Bactericidal
Narrow spectrum
Least side effects
1 and 2 make them less likely to cause resistance

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26
Q

Beta-lactams

A

All have a beta-lactam ring
Penicillins, cephalosporins, carbapenems (only human products available- no veterinary data yet)
1st line antibiotics
-cidal, narrow spectrum, less s/e
Resistance is often (but not always) due to beta-lactamase destruction of the pharmaceutically active beta-lactam ring
Bacteria that are resistant to penicillins are usually resistant to the cephalosporins and vice-versa
Patient with penicillin allergies also have allergies to other beta-lactams

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27
Q

Penicillins work against

A

Part of the beta-lactam antibiotics; contain a beta-lactam ring
Mostly kill gram + bacteria
Drug binds to the bacteria enzyme responsible for cross-linking the peptidoglycan layers that make up the cell wall
Prevents stabalization of the cell wall; bacteria die from water entering the cell
Only works on actively dividing bacteria

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28
Q

Penicillin as a 1st line antibiotic

A

Bactericidal
Bactericidal drugs have a lower risk of causing resistance when used correctly
Narrow spectrum of activity
Narrow spectrum drugs are less likely to cause resistance
Older drugs only work on Gram+
Newer broad-spectrum drugs have some Gram - activity
Fewer side effects
Because animal cells do not have cell walls

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29
Q

Hyrophilic properties of penicillin

A

Well absorbed from injection sites
Excellent volume of distribution
Drawn to inflamed tissues; can even penetrate abscesse

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30
Q

Where is penicillin metabolized and excreted

A

Not metabolized in liver
Eliminated in active form in the kidneys; also found in active form in secretions (milk)

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31
Q

Precautions while using penicillin

A

When given orally they may destroy beneficial Gram + bacteria residing in the lumen of the intestinal tract, allowing more pathogenic bacteria to proliferate
Yogurt, pre/probiotics to counteract this
Adverse reactions to penicillins are rare, but can include type I hypersensitivity reactions
Must observe withdrawal times in food animals.
Label all dispensed medications with clear instructions for proper administration and WTs

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32
Q

Resistance to penicillins

A

There is lots of resistance to the penicillins
Via plasmids that contain the gene for the beta-lactamase enzyme
Beta-lactamase cutes the beta-lactam ring so drug is no longer active
This plasmid can be shared with other bacteria and is passed to progeny→ spread of resistance
Enzyme inactivates any drug containing beta-lactam ring
Penicillins, cephalosporins, carbopenams

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33
Q

Penicillin G (PenG) works against

A

Very narrow spectrum (gram + only)

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34
Q

Penicillin G is commonly used in what animals and why

A

Comes in various injectable formulations
Formulations are NOT interchangeable
Different pharmacokinetics result in different duration of effects
Different withdrawal times

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35
Q

How to administer Penicillin G

A

Na+/K+ Pen G (aqueous) IV or IM use
Most commonly used, shortest acting (1h); 3 d WDT

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36
Q

Procaine Pen G (suspension)
is given how

A

Give IM only. NEVER give IV as it will cause sudden death due to heart block. 24 h duration
Procaine reaction in horses
Procaine will also test + at a horse show

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37
Q

Benzathine Pen G (suspension) has how long of a withdrawal time

A

Slow release formulation. 5d duration; 28d WDT

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38
Q

Aminopenicillins works against what

A

Broad spectrum = Gram + and a limited number of Gram -
Binds to the surface of Gram - cell wall and prevents bacteria from adhering to surfaces and one another (prevents colonizing)
Commonly used in SA

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39
Q

What drugs are Aminopenicillins

A

Ampicillin and Amoxicillin
Injectable and oral form

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40
Q

Extended spectrum penicillins are used to treat what and why

A

These drugs are held in reverse, used to treat severe, resistant Gram - infections
Activity against Pseudomonas and other gram - bacteria
Batter able to penetrate the outer cell wall compared to other penicillins
They are synergist when administered with aminoglycosides, and have good activity against anaerobes
E.g. Ticarcillin, piperacillin, carbenicillin

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41
Q

Potentiated penicillins are what drugs

A

amoxicillin/clavulanic acid (amoxi-clav)

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42
Q

amoxicillin/clavulanic acid work by

A

Amoxicillin which has been combined with a second drug, clavulanic acid
Clavulanic acid (or sulbactam) protect the penicillin from bacterial beta-lactamase enzymes
Clavamox®; Noroclav®; Clavaseptin®

43
Q

Side effects of penicillins

A

Fairly safe because animal cells do not have cell walls
Side effects related to disturbance of normal flora, formulations, allergy
GI issues
Most common
Only if given orally
Vomit, diarrhea, inappetance
Chemical irritation or disturbs normal flora
Will decrease if given with food; BUT, giving with food decreases absorption
May need to adjust dose or give 1h after feeding
Rapid injection IV can cause neurological signs or anaphylaxis or sudden death
allergies/anaphylaxis in animals and people can be very severe

44
Q

What happens if you give penicillin IV

A

Rapid injection IV can cause neurological signs or anaphylaxis or sudden death
Anytime a penicillin is given IV, give by slow injection (a single dose over 10-20 min)
Procaine PenG should NEVER be given IV (IM only)
Giving IV causes acute excitement and death due to local anesthetic overdose
Can occur when given IM if a small amount enters a vessel
Horse hyperalert, spooked, may collapse, lasts 2-5 minutes

45
Q

Why does penicillin cause anaphylaxis

A

allergies/anaphylaxis in animals and people can be very severe
Of all the beta-lactams, occurs most commonly with the penicillins
PenG is naturally derived from the Penicillium fungus and has the highest risk of allergy
Some animals/people with penicillin allergies may also react to cephalosporins and carbapenems
More likely if injected
Hives, swelling of throat, vomit, diarrhea, hepatitis, pruritus, vasodilation
Watch WDTs in food animals

46
Q

Cephalosporins are what type of drugs and work by

A

Recognize by “Cef” prefix
Contain the beta-lactam ring
Block cell wall synthesis
Gram + bacteria
Susceptible to beta-lactamase resistance
Same plasmid-driven mechanism as for penicillins
Concentration-dependent
Very commonly used
Names usually begin with “ceph-” or “cef-”

47
Q

5 generations of cephalosporins

A

1st generation
Oldest; gram + only
Cephalexin -commonly used orally
Cefazolin (Kefzol®)- surgical prophylaxis; slow IV over 20 min
3rd generation
Cefovecin (Convenia®)
Cefpodoxime (Simplicef®)
Ceftiofur (Excenel®-SID;Excede®-2 treatments 5 days apart)
Newer generations are broader spectrum (also get gram - and anaerobes) and have better tissue distribution

48
Q

Convenia is what type of drug and works by

A

Cephalosporins
Contains cefovecin (3rd gen)
Long acting
14 days in therapeutic range after single SQ injection
Has been over-used due to convenience; seeing increased resistance. Recommend susceptibility testing before use
Reminder: always indicate current and rect antibiotics on lab submission forms
Must be re-administered on (or before) day 14 if infection has not resolved completely

49
Q

Indications for covenia

A

Cats that are difficult to pill
UTI (off label)
Soft tissues abscesses

50
Q

Side effects of cephalosporins

A

GI issues if given orally
Most common side effect if given orally
Vomit, diarrhoea, inappetence due to chemical irritation or disruptions of GI flora
Always give with food
Needs to be written directly on the prescription label
Allergy and anaphylaxis
May or may not be related to penicillin allergy
Incidence is lower than that seen in penicillins
IM injection may be painful in LA

51
Q

Aminoglycosides are what type of drugs and work against waht

A

Recognized by “micin/mycin” suffix
Damages the cell membrane and block protein synthesis
Aerobic, gram -ve, bactericidal
Concentration dependent
Hydrophilic
Very severe adverse effects

52
Q

Commonly used aminoglycosides

A

Usually found in topical eye and ear formulations; also in topical wound ointments
Examples end in “micin (mycin)”
Gentamicin (ear drops:Mometamax® otic, Otomax®; can be used short-term IV)
Neomycin(Tresaderm®otic,Polysporin® wound ointments)
Amikacin–broadest spectrum, infusion beads,can be used short- term IV
Tobramycin–(Tobrex® ophthalmic drops)

53
Q

Ototoxic and nephrotoxic with aminoglycosides

A

TWO MAJOR adverse effects of ALL aminoglycosides are nephrotoxicity (kidney damage) and ototoxicity (damage to the auditory nerves and inner ear)
Occur commonly
Nephrotoxicity is reversible; ototoxicity is irreversible
Increased risk with systemic administration; decreased risk if used locally
Increased risk with longer duration of use
Increased risk in older patients, patients with pre-existing renal or neurological issues

54
Q

nephrotoxicity is with aminoglycosides

A

Very likely to occur if drug given systemically for more than 7 days
Drug accumulates in renal tubule cells and is directly toxic to cells
Must monitor for urine casts to detect damage to renal cells
Must monitor for plasma levels to avoid toxic levels–therapeutic drug monitoring
Increased risk if very young, very old, hypotensive, pre-existing renal disease

55
Q

Ototoxicity and neurotoxicity with aminoglycosides

A

Damage to auditory nerves (deafness) and inner ear (vestibular toxicity)
Neomycin, gentamycin most toxic
These drugs are commonly found in SA ear meds
Common adverse effect of use of topical ear meds

56
Q

Increased risk of ototoxicity and vestibular toxicity with aminoglycosides if

A

Ruptured eardrum
Broken skin
Cats
Older
Extended dosing
If underlying neurological disease

57
Q

Ototoxicity and neurotoxicity with aminoglycosides clinical signs and treatment

A

Clinical signs: loss of hearing, pain, head tilt, loss of balance, Hoarders syndrome (unequal pupils, droopy lid)
Stop meds→ flush ear with saline→ must be seen

58
Q

Safe use of aminoglycosides

A

Not a first line antibiotic
Not approved for use in food-producing animals
Based on culture and sensitivity only
Usually given as a local drug
Poor oral absorption, so should be OK if dog licks
Do not use longer than prescribed even if topical
Only use systemically under specific circumstances
Use as per label
Do not give more than recommended
Do not give longer than recommended
Follow all contraindications
Do not use on pyogenic infection sites–inactivated by pus which is acidic

59
Q

fluoroquinolones/quinolones

A

Recognized by ‘floxacin’ suffix
Newest class of antibiotic
Inhibits DNA replication; broad spectrum, -cidal
Recommended to only be used for:
Hospital-acquired infections (especially of the urogenital tract)
For other severe infections only if there is proven resistance to other older antibiotic classes
Still a reserved class in human medicine
Names end in “-floxacin”

60
Q

Using FLQs

A

Arguably over-used in vet med
Different routes available (oral and injectable)
Wide-spread and excellent tissue penetration
Treat skin, respiratory and urinary infections
Newer drugs have once-a-day oral dosing
Also found in many ear drops due to SID dosing
Commonly used to treat bacterial infections in reptiles
No quinolones approved and labeled for use in horses.

61
Q

FLQ Adverse Effects

A

Disrupts joint formation in young animals
Bubble-like lesions in cartilage
Avoid or use with caution in young or growing animals
Enrofloxacin can cause retinal damage in cats with potential for irreversible blindness
High risk of creating antibiotic resistance

62
Q

How do Tetracyclines work

A

Binds to ribosomes and blocks protein synthesis
Bacteriostatic
Broadest spectrum of all antibiotic classes
Gram + and Gram –, Mycoplasma, rickettsial organisms (Lyme, Anaplasmosis, Erlichia)
Time dependant
Lots of resistance
Up to 30 different bacterial resistance genes have been identified

63
Q

Commonly used tetracyclines

A

3 generations; vets have access to 1st and 2nd generation drugs
1st gen: tetracycline, oxytetracycline
2nd gen: minocycline, doxycycline
3rd gen (2005): reserved for human resistant cases
Seeing lots of resistance, esp to 1st generation drugs
Names end in“-cycline”

64
Q

Indications for tetracyclines

A

Commonly used in all SA and LA species
Doxycycline is the drug of choice for tick borne diseases and heartworm
Subtherapeutic doses added to feed shown to enhance growth
Poultry, calves, pigs
Banned for trade purposes in Europe, North America
Commonly used to treat respiratory, urinary and skin infections, sepsis
Including metaphylaxis of Shipping Fever

65
Q

Using tetracyclines

A

Cattle and horses do not tolerate oral dosing
Check if formulation can be given IM, IV, SQ
There are short-and long-acting injectable forms
Long-acting IM forms commonly used in food animal production (up to q5d dosing)
WDTs are very different for short- and long-acting
IV injections are ALWAYS over 10-20 min
Rapid IV will cause fatal arrhythmia and collapse
Usually PO route in SA
Give 1-2 hours apart from dairy products. If given WITH diary products, drug will bind to Ca+ and not get absorbed
Always follow with some water after administering PO

66
Q

Tetracyclines adverse effects

A

Binds to calcium; binds to bone and teeth
Causes yellow discoloration of teeth if given to young animals or pregnant/nursing animal
May slow bone growth
Avoid pregnant/growing animals
Nausea, vomit, diarrhea, inappetance
Due mostly to effects on normal flora
Will help if given with food (not dairy)
Esophageal necrosis
Occurs if pill sticks to side of esophagus
Highest risk in cats; can occur in any species
**Owners MUST flush with a syringe of water after pilling
Risk of fatal arrhythmia if given fast IV
Due to chelation of calcium in blood; Ca+ is no longer available for muscle contraction
Sudden collapse, death
Horses most susceptible

67
Q

Contracted tendons in foals can use what to treat

A

Oxytetracycline is also used to treat contracted tendons in foals
believed to chelate Ca in muscle therefore causes relaxation and allows limb to extend. Followed by bandaging/splinting.
Must be done in the first few days after birth.

68
Q

Sulphonamides (aka Sulfa Drugs)

A

Recognized by “sulfa” prefix
Anti-metabolites; inhibit folate synthesis to stop growth – bacteriostatic ; broad spectrum
Excellent tissue distribution
Goes everywhere incl. CNS, prostate, eye
Lots of resistance, drug interactions and side effects

69
Q

2 formulations of sulfa drugs

A

Feed additives stay in the GI tract and are NOT absorbed; used to treat coccidiosis in chickens
Systemic sulfa drugs are given PO, IV, IM; enter plasma and used to treat tissue infections

70
Q

Trimethoprim sulfadiazine (TMP-S)

A

Most commonly used systemic sulfa drug
“Old drug”
Occasionally used in SA, horses
Used in food animals in Canada; banned in USA

71
Q

Adverse effects of Trimethoprim sulfadiazine (TMP-S)

A

KCS – keratoconjunctivitis sicca, “dry eye”
Decreased tear production causes increased risk of corneal irritation and corneal ulcers
May be permanent
Watch for red eye, blinking, mucus coat over eyes
Allergic skin reactions/rashes
Hives, redness, pruritus, hives
Crystallization of drug in the urine
SA, dehydrated, if acidic pH
Anorexia
Bone marrow suppression
Fever and polyarthritis
Idiosyncratic fatal liver failure
Hypothyroidism
Teratogen – deformities in the neural tube due to folate deficiency
Lots of drug interactions-fatal arrhythmias if given with detomidine in horses.

72
Q

Lincosamides

A

Bacterial protein inhibitors
Bacteriostatic or cidal depending on concentration
Works against anaerobes, gram positive aerobic cocci and toxoplamsa parasites
Distributed to milk and can cause diarrhea in nursing young
Can cross placenta
Partially metabolized by liver
Contraindicated for use in animals who rely on fermentation for digestion of food e.g. horses rodents, ruminants and rabbits

73
Q

Clindamycin used for and adverse effects

A

Effective drug for use in deep pyodermas, abscesses, dental infections, bite wounds and osteomyelitis
IM, PO
Most common adverse effect is GI upset
Can happen with any route of delivery (PO or IM)
Inappetance, vomit, diarrhea
Discontinue drug usually recommended
May see hypersalivation or lip smacking in cats after PO administration.
IM injection may see pain at injection site

74
Q

Macrolides used to treat

A

Bacteriostatic by inhibiting protein synthesis
Primarily used to treat gram positive bacterial respiratory disease.
Azithromycin(Zithromax®), and Erythromycin– human drugs
Tilmicosin (Micotil®), Tylosin(Tylan®) and Tuliathromycin (Draxxin®)– Veterinary drugs

75
Q

Tilmicosin (Micotil®) used for/in/and where

A

Commonly used in beef cattle and sheep
Metaphylaxis and treatment of bovine shipping fever
Long-acting injectable, q72h
Give SQ ONLY (slows down absorption)
Highly irritating if given IM

76
Q

Improper use of tilmicosin can cause

A

Improper use can cause cardiotoxicity
Drug blocks Ca+-channels
Tachycardia, decreased cardiac output, hypotension
CAN BE FATAL
If given IV
Drug is contraindicated in horses, pigs, due to cardiotoxicity
Also reported in people handling drug

77
Q

Accidental injection of Micotil® in people can

A

Be fatal
Exposure to scratches can cause severe inflammation, pain
Low dose systemic exposure can cause dizziness, hypotension
High dose systemic injection can cause cardiac arrest (5%)
Use needle/syringe safety especially with:
Pressurized injection guns
Multi-dose syringes
Carrying loaded syringes in pockets

78
Q

Proper handling of Micotil®

A

Never attach needle to syringe containing drug until ready to use
Wear gloves
Avoid eye contact (can be absorbed via the conjunctiva)
Never work alone with this drug
Ensure proper restraint/chute system
Lots of fatal drug interactions, so must be able to tell emergency workers name of drug
Wash immediately in the event of spills or accidental contact

79
Q

Chloramphenicol used to treat and how to handle

A

Used to treat a variety of anaerobic bacterial infections in small animal and horses.
Banned from use in food animals
Due to risk of fatal aplastic anemia in humans.
Wear gloves when handling and avoid inhalation of powder.
Wash hands after handling tablets or capsules
Need to ensure owners are aware of fatal effects
Inhibits Cyp450 enzymes

80
Q

Florfenicol - Nuflor® is used in

A

Similar to Chloramphenicol but lacks the functional group that causes aplastic anemia
Commonly used in feedlot cattle and swine
Only approved for use in these 2 species
WDT
Cattle
Metaphylaxis and treatment of bovine shipping fever; foot rot and infectious bovine keratoconjunctivitis
Long-acting IM injection
Swine
Added to feed for respiratory infections.

81
Q

Florfenicol Adverse Effects

A

Local tissue reaction
Can cause tissue loss at slaughter-go for neck/chest.
Very bad if more than 10 ml per site given IM
Inappetance, diarrhea
Decreased water consumption
Reversible bonemarrow suppression
More common if chronic high dose
Increased residues in the environment if using for metaphylaxis in feedlots
Banned in dairy
Avoid in horses due to possible fatal acute colitis

82
Q

Metronidazole (Flagyl®) used in

A

Bacterocidal
Commonly used to treat SA diarrhea
Anti-protozoal (Coccidia, Giardia,trichomonas…)
Clostridia and other anaerobes (hoof abcesses – horses)

83
Q

How to give metronidazole and side effects

A

Can be given on an empty stomach
Has a bitter taste and can cause vomiting and anorexia in small animals
Must dilute and neutralize if giving IV
Treated cattle must not be slaughtered for food
Side effects can occur at therapeutic dose:
Neurological effects (ataxia , vestibular signs, head tilt, abnormal nystagmus, disorientation)
Tremor and seizures

84
Q

Prostora®

A

Probiotic made by Iams
Live bacteria are genetically modified to be resistant to metronidazole
Given with metronidazole.

85
Q

Limiting Antibiotic Resistance

A

Right drug for the right bug
Avoid sending ABCs to pacify owners
Perform culture and sensitivity testing to ensure correct drug
Avoid prophylactic use
Maintain therapeutic range
Correct mg/kg dose
Correct frequency of dosing
Correct route of administration
Avoid ELDU
Treat until the infection has resolved
Do not stop just because clinical signs have resolved
Have patient come back for recheck
Ensure negative culture
Only dispense one course at a time
No “standing” repeats for antibiotics
Prevents hoarding and/or intermittent use
Preventing residues (adhering to WDTs)
Avoid ELDU
Also address hygiene, husbandry, wound care
Client communication to ensure owner compliance

86
Q

Client Communication for antimicrobials

A

Explain dosing frequency
Ex. q12h (not BID)
Finishing the prescribed amount
Explain need to complete a full course; do not stop just because symptoms have resolved
Do not stock-pile, do not give excess
Explain about resistance issues
Show owners how to give
Poor compliance is often because of difficulty/inconvenience
Emphasize need for rechecking to ensure infection has resolved
Go over side effects
GI upset is very common for PO routes
Most common signs of GI upset?
Give with food (most antibiotics)
Tetracyclines – wash down after pilling, avoid giving with dairy
Common side effects
Give WDT if food animal OR horse
Follow-up
To identify adverse effects when they occur

87
Q

Overview of Antifungals

A

Used to treat mycoses (fungi diseases)
Infections can be superficial (Malassezia, Dermatophytes) or systemic (blastomycosis)
Mechanism of action
Damage cells; usually cell membranes
Blocks cell replication
Drug must be protected from light

88
Q

Adverse Effects of Antifungals

A

Lower therapeutic index than antibiotics
Fungi and animal cells are both eukaryotic
Lots of common structures and proteins
Consider all to be teratogenic:
Never use in any pregnant animal
Wear gloves to handle if pregnant

89
Q

Classes of Antifungals

A

Polyenes
Amphotericin B, Nystatin,
Azoles
Ketoconazole (Nizarol®)
Itraconazole, fluconazole
Antimetabolites
Superficial anti-dermatophytes
Griseofulvin B

90
Q

Polyenes work for

A

Examples: nystatin, amphotericin B
Binds to sterols located in fungal cell membrane and punches holes into cells
Very severe side effects if systemic
Binds cholesterol in patient’s cell membranes
Kidney damage in 80% patients at therapeutic dose
Severity of disease must justify systemic use

91
Q

Formulations of Polyenes

A

IV injectable –amphotericin B
To treat very severe systemic mycosis
Rapid onset (hours)
Will cause systemic toxicity
Topical polyenes - nystatin
Local application decreases systemic toxicity
Commonly found in skin creams (polysporin, diaper creams) and ear drops
Very poor oral bioavailability

92
Q

Azoles are

A

1 choice of anti-fungal when possible due to fewer side-effects

“-azoles”
ketoconazole (Nizarol®) (oral, topical) itraconazole (oral and topical; cats)
fluconazole (oral, IV)
miconazole (topical, infusion)
clotrimazole (topical, infusion)

93
Q

Mechanism of Azoles

A

Disrupts fungal cell membrane synthesis
Fewer side effects than previous class; but slower onset of action (5-10 days)
Oral, injectable and topical formulations
Commonly used:
Ringworm
Allergic yeast dermatitis
Very severe yeast otitis

94
Q

Side effects of azoles

A

GI upset – nausea, vomit, inappetance
Can decrease by splitting single large dose into smaller doses throughout day
Hepatotoxicity
Older animals, pre-existing liver damage, prolonged treatment
Inhibits cytochrome P450 activity
Can increase toxicity of other drugs
Decreases steroid production
Suppresses adrenal gland function
ketoconazole is used to treat Cushing’s disease; it damages the adrenal glands in a reversible manner
Can cause an iatrogenic Addison’s disease
Teratogenic

95
Q

Griseofulvin is used for

A

Still used, but less common than in past
Treatment of superficial dermatophytoses (ringworm) in dogs, cats, horse
Oral formula only

96
Q

Griseofulvin adverse effects

A

GI effects: inappetance, vomit, diarrhea
Teratogen - NEVER USE IN PREGNANT ANIMALS
Cats more susceptible to toxic effects
Teratogenic in cats

97
Q

Antivirals work against

A

Viruses cannot replicate on their own
MUST infect a host cell and use the host cell’s enzymes to replicate
Opportunities to stop virus infections:
Inactivate the free virion
Prevent attachment/entry
Kill virus factories (i.e., infected host cells)
Block viral enzymes involved in replication – very few of these; most are hard to access and rapidly mutate

98
Q

Preventing versus Treating viruses

A

Viruses are hard to treat, because would require damaging the body’s own cells that virus has infected
Antibiotics do NOT work on viruses
Knowing whether a disease is caused by a virus is important when talking to owners
Most effective way to treat a virus infection is to boost the body’s own immune response to the virus
Vaccines

99
Q

Summary of Antivirals

A

Preventing transmission and vaccinations are keystone to control of viral infections
Limited number of anti-virals exist
Limitations due to:
Virus have limited targets
Limited access due to intracellular infection
Risk/damage to infected host cells

100
Q

AZt is

A

Drug to treat HIV in humans
Inhibits viral RNA replication enzymes
Has been used treat FIV ($$$$)

101
Q

Acyclovir is

A

Treat herpes virus (ex.feline herpesvirus)
Inhibits viral DNA replication
Adverse effects: may cause GI upset if given orally

102
Q

Class I interferons work against

A

Non-specific anti-viral; works against all viruses
Part of innate immune response and blocks entry of virus into adjacent cells
Questionable efficacy, but few side effects
Will use to treat severe FURD, FeLV, FIP

103
Q

Lysine works for

A

Amino acid
Nutraceutical; OTC
Anti-herpes virus activity (respiratory disease cats)
Available as powders, foams, gels, treats

Pharmocology (10 decks)

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