Unit 3 - Antimicrobials

Question 1

What are antimicrobials?

Answer 1

Compounds used to kill or inhibit microbial growth

Question 2

What types of antimicrobials are there and what defines them/

Answer 2

Target organism or Spectrum of activity - bacteria, fungi, virus, protozoan
-static (inhibition of replication but does not directly kill) - bacteriostat, fungistat, virustat, protozoistat
-Cidal (kills) - bacteriocide, fungicide, virucide, protozoicide

Question 3

What is antimicrobial therapy? What are some factors involved in choosing an appropriate drug?

Answer 3

Goal is to kill or inhib specific pathogens while not harming the host
Factors involve susceptible microorganism (determined based on culture and sensitivity)
Access the site of infection at appropriate concentrations
Host tolerance to the drug

Question 4

What is microbial susceptibility?

Answer 4

Based on minimum inhibitory concentration
it is strain and antimicrobial specific
Compare maximum tolerated dose (MTD) to MIC.
Compare drugs therapeutic range with its MIC classifies a pathogen as sensitive or resistant to that drug

Question 5

Is a microbe resistant, or sensitive if MIC>MTD, what about MIC<MTD

Answer 5

IF MIC greater than MTD = resistant
IF MIC less than MTD = sensitive

Question 6

What two princibles dictate whether a microbial works?

Answer 6

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

Question 7

What is antimicrobial resistance?

Answer 7

capability of an organism to survive in the presence of antimicrobials and passes it on to other microbes via chromosomes (vertical transmission) and plasmids (horizontal transmission)
May result from random genetic mutations or the inappropriate use of antimicrobials
Causes selection pressure which results in large resistant populations

Question 8

Why is antibiotic resistance important?

Answer 8

Risk of resistance inc when antibiotics are used inappropriately bc anytime bact is exposed to an ABC and not killed (broad spectrum, bacteriostatic, under-dosing below MIC)
Unnecessary prescription - metaphylaxis/prophylaxis, viral infections (not all bugs need drugs)
Poor owner compliance
Unnecessary exposure - exposure thru residues, failures to follow WDTs

Question 9

What are drug residues?

Answer 9

when a food-animal is treated with a medication, food products (meat, milk, eggs) must not contain drug residues from treatment
Residues are unacceptable bc of human hypersensitivities and proliferation of resistant microbial populations

Question 10

How can drug residues be avoided?

Answer 10

ensure WDT for drugs are adhered to
Label all dispensed medications with clear instructions for proper administration and include WDTs

Question 11

What is antimicrobial stewartship?

Answer 11

some antibiotics should be “off limits” - save the big guns for the big bugs. ex MRSA (methicillin resistance staph. aureus)
this includes prescription feed additives
ideally treat based on culture and sensitivity

Question 12

What are the 5 basic mechanisms of antibiotic action against bacteria cells?

Answer 12

1. inhibition of cell wall synthesis (most common)
2. inhibition of protein synthesis (translation) 2nd largest class
3. Alteration of cell membranes
4. Inhibition of nucleic acid synthesis
5. Antimetabolite activity

Question 13

How does inhibiting the cell wall synthesis work?

Answer 13

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

Question 14

How dows inhibiting protein synthesis thru translation work?

Answer 14

Disruption of protein synthesis by combining with ribosome and interfering with mRNA or tRNA
blocks cell from dividing and results in cell death
can also cause damage to cell membrane

Question 15

How can altering bacteria cell membranes help the mechanism of action antibiotics?

Answer 15

these drugs make the cell membrane “leaky”
drug molecules are more readily enter the cell
cytoplasmic components are more readily able to escape the cell

Question 16

How does inhibiting nucleic acid synthesis work in favor of antibiotics?

Answer 16

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

Question 17

What do newer antibiotics have in regards to inhibiting nucleic acid synthesis?

Answer 17

They 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 structures only found in bacteria and not mammalian cells

Question 18

What is antimetabolite activity?

Answer 18

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

Question 19

What does the ideal antibiotic protocol include

Answer 19

1. organism identified and susceptible to drug chosen
2. Drug is bacteriocidal and narrow spectrum (bateriostatic drug, patient must have a functioning immune system)
3. Good distribution to the site of infection
4. High TI; few side effects; patient must be able to tolerate the tx
5. no ability to acquire resistance
6. dosing regiment easy to follow
7. patient returns for follow-up to ensure therapeutic goal reached

Question 20

What are 3 goals when using antibiotics

Answer 20

1. resolution of bacterial infection
2. no or acceptable side effects
3. no resistance

Question 21

What are 1st line antibiotics?

Answer 21

the go to antibiotics
3 characteristics
1. bacteriocidal, lower rist of causing resistance when used correctly
2. narrow-spectrum - older drugs only work on gram+, newer broad spect have some gram - activity
3. least side effects - bc animal cells do not have cell walls
1 and 2 make them less likely to cause resistance

Question 22

What are unique about beta-lactams
a

Answer 22

all have beta-lactam rings
only human products available
1st line antibiotics - cidal, narrow spectrum, less S/E
Resistance is often bc of beta-lactamase destruction of pharmaceutically active beta-lactam ring
bact that are resistant to penicillins are usually resistant to the cephalosporins and vice-versa
patients with penicillin allergies also have allergies to other beta-lactams

Question 23

What do penecillins mostly kill?

Answer 23

Gram+ bact
drug will bind to bact enzyme responsible for cross-linking the peptidoglycan layers that make up the cell wall
Prevents stabilization of the cell wall; bact die from water entering the cell
only works on actively dividing bact

Question 24

What are some properties of penicillins?

Answer 24

hydrophilic - well absorbed from injection sites w/ excellent volume of distribution, drawn to inflamed tissues; can penetrate abscesses
Not metabolized in river
eliminated in active form in kidneys; also found in active form in secretions (milk)

Question 25

What are some precautions when with penicillin?

Answer 25

when given PO, may destroy Gram+ bact residing in lumen of int. tract, allowing more pathogenic bact to proliferate (yogurt, pre/probiotics to counteract this) Adverse reactions to penicillins are rare, but can include Type 1 hypersensitivity reactions Must observe WDT in food animals - label all dispensed meds w/ clear instructions for proper admin and WDT

Question 26

What is penicillin resistance?

Answer 26

Via plasmids that contain the gene for beta-lactamase enzyme (beta-lactamase cuts the beta-lactam ring so drug is no longer active) This plasmid can be shared w/ other bact and is passed to progeny > spread of resistance Enzyme inactivates any drug containing the beta-lactam ring (penicillins, cephalosporins, carbopenams

Question 27

What are the different penicillin classes?

Answer 27

Naturally occuring penicillins Aminopenicillins (broad spectrum) Beta-lactamase resistant penicillins (penicillinase resistant) Extended-spectrum penicillins potentiated penicillins (resistant to the B-lactamase enzyme)

Question 28

What is penicillin G?

Answer 28

Very narrow spectrum (gram- only) Common use in LA - formulations NOT interchangeable but various injectable formulations, diff pharmacokinetics = diff duration of effects, diff WDT Na/K Pen G (aqueous) IV or IM use (most common, shortest action 1hr; 3d WDT) Procaine PenG suspension (IM only, NEVER Iv bc of heartblock. 24 hr, reaction in horses, will test pos at shows) Benzathine peng (suspension), slow release formulation, 5d, 28 WDT

Question 29

What is unique about aminopenicillins?

Answer 29

Broadspectrum penicillins gram + and a limited # of gram- binds to surface of gram- cell wall and prevents bact from adhering to surfaces and one another (prevents colonizing) common in SA Ampicillin and Amoxicillin - injectable and oral form

Question 30

What are unique about extended-spectrum penicillins?

Answer 30

drugs held in reserve, used to treat severe, resistant gram- infections activity against Pseudomonas and other gram- bact (better able to penetrate outer cell wall compared to other penicillins) synergistic when admind with aminoglycosides and have good activity against anaerobes Ex. ticarcillin, piperacillin, carbenicillin

Question 31

WHat are potentiated penicillins?

Answer 31

amoxicillin/clavulanic acid (amoxi-clav) amoxicillin which has been combined with a second drug, clavulanic acid Clav acid protect the penicillin from bact b-lactamase enzymes Clavamox, norovlac, clavaseptin

Question 32

What are some side effects of penicillins?

Answer 32

fairly safe bc animal cells do not have cell walls so side effects are related to disturbance of normal flora, formulations and allergies 1. GI issues 2. Rapid injection IV can cause neurological signs or anaphylaxis or sudden death 3. Allergies/anaphylaxis in animals and people can be very severe

Question 33

How do GI issues present as side effects from penicillins?

Answer 33

most common, only if given orally, vomit/diarrhea/inappetance chemical irritation or disturbs normal flora will dec if given food; but, with giving food dec absorption (may need to adjust dose or give 1h after feeding

Question 34

How might rapid injection IV of penicillions present for side effects?

Answer 34

can cause neurological signs or anaphylaxis or sudden death anytime given IV, give slow injection (1 dose over 10/20 min) procain PenG NEVER IV, IM only bc giving IV causes acute excitement and death due to local anesthetic OD can occur when given IM if small amount enters a vessel Ex. horses become hyperalert, spooked, may collapse, last 2-5 mins

Question 35

With penicillin side effects, how might allergies/anaphylaxis present?

Answer 35

Can be very severe of all the beta-lactams, occurs most commonly with penicillins - PenG naturally derived from the Penicillium fungus and has highest risk of allergy Some anims/peopls w/ penicillin allergies may react to cephalosporins/carbapenems more likely if injected Hives, throat swlls, vomit, diarrhea, hepatitis, pruritus, vasodilation WDT in food animals, watch it

Question 36

What are characteristics of cephalosporins?

Answer 36

contains the beta-lactam ring blocks cell wall synthesis gram+ bact susceptible to beta-lactamase resistance (same plasmid-driven mechanism as for penicillins) concentration- dependant very commonly used names begin with ceph or cef

Question 37

What happens with the 1st gen of cephalosproins?

Answer 37

1st, oldest, gram+ only cephalexin - common PO Cefazolin (surgical prophylaxis, slow IV over 20 min)

Question 38

What cephalosporins are cluded with the 3rd gen?

Answer 38

Cefovecin, cefpodoxime, ceftiofur(Ex, excede - 2 tx 5 days apart) newer gens broader spectum (also get gram- and anaerobes) have better tissue distribution

Question 39

What is convenia?

Answer 39

Cephalosproin, contains cefovecin (3rd gen), long acting 14d in therapeutic range after single SQ injection Indicated for cats difficult to pill, off label UTI, soft tissue abscesses Has been over-used due to convenience; seeing inc resistance. recommend susceptibility testing b4 use -always indicate current and recent antibiotics on lab submission forms must readmin on(or before) day 14 if infection not resolved completely

Question 40

What are the side effects of cephalosporins?

Answer 40

1. GI issues if given orally - vomit, diarrhea, inappetance due to chemical irritation or disruption of GI flora, ALWAYS give WITH FOOD, needs to be written on the label 2. Allergy and anaphylaxis - may or may not be related to penicillin allergy, incidence is lower than that seen in penicillins 3. IM injections may be painful in lg anim

Question 41

What are aminoglycosides?

Answer 41

damages cell membrane and blocks protein synth aerobic, gram -, bacteriocidal Concentration dependant hydrophilic very severe adverse effects

Question 42

What are some commonly used amingoglycosides?

Answer 42

usually found in topical eye/ear/wound formulations/ointments Ex. end in micin(mycin) Gentamicin (ear drogs; can be used short term IV) Neomycin (polysporin wound ointments) Amikacin (broadest spectrum, infusion beads, can be used short-term IV) Tobramycin (ophthalmic drops)

Question 43

What are the two most MAJOR adverse effects of ALL aminoglycosides? How does it occur, are they reversible or irreversible?

Answer 43

Nephrotoxicity (kidney damage) and ototoxicity (damage to the auditory nerves and inner ear) occur commonly nephro is reversible; cytotoxicity is irreversible

Question 44

What increases the risk of ototoxic and nephrotoxicity?

Answer 44

Inc risk w/ systemic admin; dec is used locally Inc w/ longer duration of use Inc in older patients and pre-existing renal or neurological issues

Question 45

What is nephrotoxicity?

Answer 45

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 cats to detect damage to renal cells must monitor for plasma lvls to avoid toxic lvls - therapeutic drug monitoring inc risk if very young, very old, hypotensive, pre-existing renal dz

Question 46

What is ototoxicity and neurotoxicity

Answer 46

damage to auditory nerves (deafness) and inner ear (vestibule toxicity) From neuomycin, gentamycin most toxic (common in SA ear meds) Common adverse effect of topical ear meds

Question 47

What increases the risk of ototoxicity and vestibular toxicity? What are the clinical signs? If you see them, what should you do before they are seen?

Answer 47

ruptured ear drum, broken skin, cats, older, extended dosing, if underlying neurological dz Clin signs: loss of hearing, pain, head-tilt, loos of balance, horner's syndrome (unequal pupils, droopy lid) Stop meds > flush ear w/ saline > must be seen

Question 48

How can we use aminoglycosides safely?

Answer 48

not a first line antibiotic not approved for use in food-prod anims based on culture/sensitivity only Usually given as local drug bc poor oral absorption so 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/longer than recommended, follow all contraindications Do not use on pyogenic infection sites - inactivated by pus which is acidic)

Question 49

What are fluoroquinolones?

Answer 49

newest class of antibiotics inhibits DNA replication; broad spectrum, -cidal Reccomended use: 1. hospital-aqcuired infections (especially of the urogenital tract), 2. For other severe infections only if there is proven resistance t other older Ab classes still a reserved class in human meds ends w/ -floxacin Enrofloxacin (baytril), danofloxacin (advocin)

Question 50

How do we use FLQ's?

Answer 50

arguably over-used in vet med Diff routes available (oral/injectable) wide-spread and excellent tissue penetration - tx skin, resp and urinary infections Newer drugs have 1x/d oral dosing also found in many ear drops due to SID dosing commonly used to tx bact infections in reptles Not approved or labeled for use in horses

Question 51

What are adverse effects of FLQ?

Answer 51

1. Disrupts joint formation in yg animals - causes bubble-like lesions in cartilage, avoid or use w/ caution in yg/growing animals, enrofloxacin can cause retinal damage in cats w/ potential for irreversible blindness 2. High risk of creating antibiotic resistance

Question 52

What are some characteristics of tetracyclines?

Answer 52

binds to ribosomes and blocks protein synth, bacteriostatic, broadest spectrum of all antibiotic classes ( gram +/-, mycoplasma, rickettsial organisms like lyme, anaplasmosis, erlichia) Time dependant lots of resistance - up to 30 diff bact resistance genes have been identified

Question 53

What are some commonly used tetracyclings?

Answer 53

3 gens; vets have access to 1 and 2, 3 (2005) is reserved for human resistant cases Gen 1: tetracycline, oxytetracycline Gen 2: minocycline, doxycycline Seeing lots of resistance, esp to 1st gen Ends in -cycline

Question 54

What are the indications for tetracyclines?

Answer 54

Commonly used in all SA and LA species Doxycycline is drug of choice for tick borne dz and heartworm subtherapeutic doses added to feed shown to enhance growth in poultry, calves, pigs but is banned for trade purposes in Europe, N. Am Common to tx resp, urinary and skin infections, sepsis - including metaphylaxis of shipping fever

Question 55

What do we need to keep in mind if we use tetracyclines?

Answer 55

cattle and horses do not tolerate oral dosing Check if formulation can be given IM, IV or SQ There are short vs long-acting injectable forms Long-acting IM forms are common in food animal prod with up to every 5/d dosing WDTs are very short for both acting IV injections ALWAYS over 10-20mins bc rapid IV will cause fatal arrhythmia and collapse Usually PO route in SA - give 1-2hrs apart from dairy products. If given WITH dairy products, drugs will bind to Ca+ and not get absorbed, always follow with some water after admin PO

Question 56

What are the adverse effects of using tetracyclines?

Answer 56

1. Binds to Ca, bone and teeth - causes yellow discoloration of teeth if given to yg anims/pregnant/nursing anims, may slow bone growth, avoid in preg/growing anims 2. Nausea, vomit, diarrhea, inappetance - effects normal flora, helps if given w/ food (not dairy 3. Esophageal necrosis - occurs if pill sticks to side of esophagus. Highest risk in cats, ** owners MUST flush w/ syringe of water 4. Risk of Fatal arrhythmia if given fast IV - due to chelation of Ca in blood; Ca no longer available for muscle contraction, sudden collapse, death, horses most susceptible

Question 57

What tetracycle is used to treat contracted tendons in foals? How do we believe it works?

Answer 57

Oxytetracycline believed to chelate Ca in muscles, therefore causes relaxation and allows limb to extend (followed by bandaging/splinting) must be done in the first few days after birth

Question 58

What are sulfonamides?

Answer 58

Sulfa drugs w/ "sulfa" prefixes Anti-metabolites that inhib folate synth to stop growth - bacteriostatic; broad spectrum excellent tissue distribution - goes everywhere incl. CNS, prostate, eye Lots of resistance, drug interactions and side effects 2 formulations 1. Feed additives stay in GI tract and are NOT absorbed; to tx coccidiosis in chickens 2. Systemic sulfa drugs given PO, IV, IM; enter plasma to tx tissue infections

Question 59

What is trimethoprim-sulfadiazine (TMP-S)?

Answer 59

Most commonly used systemic sulfa drug. "old drug". Occasionally used in SA, horses used in food anims in CAD; banned in USA

Question 60

What are the adverse effects of TMP-S?

Answer 60

Trimethoprim-Sulfadiazine 1. KCS - keratoconjuctivitis sicca or Dry eye: dex tear prod causes inc risk of corneal irritation and corneal ulcers, may be perma., watch for red eye, blinking, mucus coat over eyes 2. Allergic skin reactions/rashes  Hives, redness, pruritus, hives 3. Crystallization of drug in the urine  SA, dehydrated, if acidic pH 4. Anorexia, 5. Bone marrow suppression 6. Fever and polyarthritis, 7. Idiosyncratic fatal liver failure, 8. Hypothyroidism 9. Teratogen – deformities in the neural tube due to folate deficiency, 10. Lots of drug interactions-fatal arrhythmias if given with detomidine in horses.

Question 61

How are lincosamides and macrolides recognized by?

Answer 61

"mycin" ending, aminoglycosides also have same ending

Question 62

What are lincosamides?

Answer 62

bact protein inhibitors bacteriostatic or cidal depending on conc, works against anaerobes, gram + aerobic cocci and toxoplasma parasites distributed to milk and can cause diarrea in nursing young, can cross placenta, partially metabolized by liver contraindicated for use in anims who rely on fermentation for digestion of food ex. horses, rodents, ruminants and rabbits

Question 63

What is clindamycin? Most coomon adverse ffect?

Answer 63

effecting drug for use in deep pyodermas, abscesses, dental infections, bite wounds and osteomyelitis. Given IM or PO Most common adverse effect is GI upset can happen with any admin route (po or IM) inappetance, vomit, diarrhea, discontinue use usually recommended, may see hypersalivation or lip smacking in cats after PO admin, IM injection may see pain at injection site

Question 64

What are macrolides?

Answer 64

bacteriostatic by inhib protein synth primarily used to tx gram+ bacterial resp dz Tilmicosin, tylosin and tuliathromycin (draxxin) vet drugs

Question 65

What is tilmicosin?

Answer 65

Micotil trade name - common in beef cattle/sheep Metaphylaxis and tx of bovine shipping fever Long acting injectable, q72h Give SQ only (slows down absorption as highly irritating if given IM Improper use can cause cardiotoxicity by blocking Ca channels, tachycardia, dec cardia output, hypotension, CAN BE FATAl - if given IV, drug is contraindicated in horses, pigs, due to cardiotoxicity Also reported in people handling drug

Question 66

What happens with accidental injection of micotil in people?

Answer 66

Can be fatal exposure to scratches can cause severe inflam, pain, low doze systemic exposure can cause dizziness, hypotension. High doze systemic injection can cause a 5% cardiac arrest Use needle/syringe safety especially w/ pressurized injection guns, multi-dose syringes, carrying loaded syringes in pockets

Question 67

What are some handling precautions to heed when using micotil?

Answer 67

never attach needle to syringe containing drug until ready to use wear gloves, avoid eye contact - can be absorbed via conjunctiva) never work alone with this drug, ensure proper restraint/chute system, lots of fatal drug interactions, so must be able to tell emerg workers name of drug, wash immediately in event of spills or accidental contact

Question 68

What is chloramphenicol and its handling precautions

Answer 68

Chloramphenicol - used to tx a variety of anaerobic bact infections in sm anims and horses, banned in food anims bc risk of fatal aplasic 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, inhibs cyp450 enzymes

Question 69

What is florfenicol - nuflor?

Answer 69

similar to choramphenicol but lacks functional group that causes aplastic anemia Common in feedlot cattle/swine, only approved for ^^, WDT Cattle: metaphylaxis and tx of bovine shipping fever, foot rot and infectious bovine keratoconjuctivitis, long-acting IM inject Swine: added to feed for resp infections

Question 70

What are the adverse side effects of florfenicol?

Answer 70

1. Local tissue reaction - can cause tissue loss @ slaughter- go for neck/check, very bad if more than 10ml/site given IM 2. Inappetance, diarrhea 3. Dec water consumption 4. Reversible bonemarrow suppression 5. inc residues in enviro if using for metaphylaxis in feedlots Banned in dairy, avoid in horses due to possible fatal acute colitis

Question 71

What is metronidazole?

Answer 71

Bacteriocidal Common to tx SA diarrhea. Anti-protzoal (coccidia, giardia, trichomonas), clostridia and other anaerobes (hoof abcesses - eq) can give on empty stomach but may cause vomit/anorexia in SA Must dilute and neutralize if IV treated cattle cannot be slaughtered for food

Question 72

What are some side effects @ therapeutic dose for metronidazole?

Answer 72

neurological effects (ataxia, vestibular signs, head tilt, abnormal nystagmus, disorientation) tremor and seizures

Question 73

What is prostora

Answer 73

probiotics made by Iams Live bact genetically modified to be resistant to metronidazole and given with ^^

Question 74

How can we limit antibiotic resistance?

Answer 74

1. right drug for right bug 2. maintain therapeutic range 3. tx until infection resolved 4. only dispense 1 course @ a time 5. Preventing residues (WDTs) 6. Address hygiene, husbandry, wound care 7. Client communication to ensure owner compliance

Question 75

How does giving the right drug for the right bug limit antibiotic resistance?

Answer 75

avoid sending ABC's to pacify owners perform culture and sensitivity testing to ensure correct drug avoid prophylactic care

Question 76

How does giving the maintaining the therapeutic range limit antibiotic resistance?

Answer 76

correst mg/kg dose, correct frequency of dosing, correct route of admin, avoid ELDU

Question 77

How does treating the infection until its resolved limit antibiotic resistance?

Answer 77

ensure negative culture, have patient back for recheck, do not stop bc sings have resolved Will be in subtherapeutic range and still be present in the body!!

Question 78

How does only dispensing one course at a time limit antibiotic resistance?

Answer 78

no "standing" repeats for antibiotics prevents hoarding and/or intermittent use

Question 79

What are important things to do in regards to client communication?

Answer 79

1. explain dosing frequency 2. Finishing the prescribed amount 3. Show owners how to give 4. Emphasize need for rechecking to ensure infection has resolved 5. Go over side effects 6. Give WDT if food animal OR horse 7. Follow-up

Question 80

What is the purpose of antifungals? Mechanism of action?

Answer 80

Used to treat mycoses or fungi dz's Infections can be superficial (malassezia, dermatophytes) or systemic (blastomycosis) Mechanism - damage cells; usually cell membranes, blocks cell replication drugs must be protected from light

Question 81

What are some adverse effects of antifungals

Answer 81

Lower TI than antibiotics - fungi and animal cells are both ukaryotic, lots of common structures and proteins Consider al to be teratogenic - never use in any pregnant animal, wear gloves if you are pregnant

Question 82

WHat are the different classes of antifungals?

Answer 82

polyenes - amphotericin B, nystatin azoles - Ketoconazole, itraconazole, fluconazole Antimetabolites superficial anti-dermatophytes - griseofulvin B

Question 83

What are polyenes?

Answer 83

ex. nystatin, amphotericin B binds to sterols loc 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% of patients @ therapeutic dose) Severity of dz must justify systemic use

Question 84

What formulations of polyenes are there?

Answer 84

1. IV injectable - amphotericiin B to tx severe systemic mycosis, rapid onset (hours), will cause systemic toxicity 2. Topical polyenes - nystatic local application dec systemic toxicity commonly found in skin creams (polysporin, diaper creams) and ear drops, very poor oral bioavailability

Question 85

What are azoles?

Answer 85

#1st choice of antifungals when possible due to fewer side-effects ketoconazole, fluconazole disrupts fungal cell membrane synthesis fewer side effects than polyenes, but slower onset of action 5-10d oral, injectable and topical formulations commonly used in ringworm, allergic yeast dermatitis, very severe yeast otitis

Question 86

What are the side effects of azoles?

Answer 86

1. GI upset - nausea, vomit, inappetence. Can dec by splitting single lg dose to sm ones throughout the day 2. Hepatotoxicity - older anims, pre-existing liver damage, prolonged tx 3. Inhibs cytochrome P450 activity 4. Dec steroid prod - suppresses adrenal gland func. ketoconazole to tx cushings dz; damages adrenal glans in reversible manner. Can cause iatrogenic addison's dz 5. Teratogenic

Question 87

What is griseofulvin?

Answer 87

tx of superficial dermatophytoses (ringworm) in k9, fel, eq oral formula only adverse effects: GI effects - inappetence, V/D, teratogenic (never use in preg anims) cats: more susceptible to toxic effects

Question 88

What are virus infections? How can we stop virus infections?

Answer 88

Cannot replicate on their own Must infect cell and use host cell's enzymes to replicate 1. inactivate free virion 2. Prevent attachment/entry 3. kill virus factories (infected host cells) 4. block viral enzyme involved in replication -very few of these; most are hard to access and rapidly mutate

Question 89

How do we prevent and treat viral infections?

Answer 89

txing is hard bc it damages body's own cells Antibiotics do NOT work Most effective to tx is to boost body's immune response by vx's

Question 90

What is AZT?

Answer 90

An antiviral drug to treat HIV in humans inhibs viral RNA replication enzymes has been used to tx FIV ($$$)

Question 91

What is acyclovir?

Answer 91

Vet antiviral treats herpes virus (feline herpesvirus) inhibs viral DNA replication GI s/e if oral

Question 92

What are class 1 interferons?

Answer 92

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 used to treat severe FURD, FeLV, FIP

Question 93

What is lysine?

Answer 93

An amino acid nutraceutical; OTC anti-herpes virus activity (resp dz in cats) available as powders, foams, gels, treats

Question 94

Give a summary of antivirals

Answer 94

preventing transmission and vx's are keystone to control viral infections limited # of anti-virals exist limitations due to virus have limited targets limited due to intracellular infection risk/damage to infected host cells