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wk5 Flashcards

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1
Q

Classifications

of Antibioitics

A

Spectrum of activity
Type of microorganism it fights
Bacteria, viruses, fungi, protozoa

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2
Q

Goals of Antimicrobial Therapy

A

Kill or disable pathogens without killing the host

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3
Q

Considerations for Antimicrobial Therapy

A

Pathogen must be SUSCEPTIBLE to the drug
Drug must REACH SITE OF INFECTION in high enough [ ] to kill or inhibit the pathogen
Animal must TOLERATE high [ ] of the drug
Other factors
Client compliance
Cost

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4
Q

MIC

A

Minimum inhibitory concentration
Lowest [ ] of drug which will inhibit growth
Antimicrobial must reach infection site in high enough [ ] to exceed the MIC

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5
Q

SENSITIVE

A

MIC is low enough to not produce significant side effects in the patient

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6
Q

RESISTANT

A

MIC is so high that there are significant side effects

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7
Q

Antibiotic Resistance

A 
Genetic changes 
Mutations of chromosomes
R plasmids
Additional piece of DNA responsible for antibiotic resistance
“R” = “resistance”
Transferred to other bacteria
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8
Q

Plasmid

A

A circle of double-stranded DNA that is separate from the chromosomes, and which is found in bacteria and protozoa. A plasmid contains genes normally not essential for cell growth or survival.

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9
Q

How can resistance be prevented?

A

Administer the appropriate dose at correct intervals, for the appropriate time, & in the appropriate manner
Educate clients importance of following the instructions, including giving for the entire prescribed time

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10
Q

How does Resistance happen?

A

Inappropriate use of antimicrobials

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11
Q

Residue

A

Presence of a drug or chemical in animal tissues or food products
Adm of drug or chemical to animal
Contamination of food
Most antimicrobial residues are not degraded by cooking or pasteurization
Exposure can cause 2 effects in humans
Hypersensitivity
Killing off of susceptible (beneficial) GIT bacteria leaving resistant (pathogenic) bacteria to proliferate

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12
Q

What are withdrawal times?

A

Use of drugs in animals intended for food must be withdrawn a specific number of days
Allows enough time for drug to be excreted

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13
Q

sites that antimicrobials may effect to kill or inhibit bacteria or fungi

A

Cell wall
Cell membrane
Inhibit protein synthesis
Interfere with critical enzymes or bind with intermediate compounds the bacteria need
Impair production of bacterial nucleic acids (RNA and DNA)

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14
Q

How drugs work on Cell wall

A

drugs work while cell wall is forming during bacterial division; bacteria are lysed as they draw in water thru osmosis
Penicillin, cephalosporins

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15
Q

Cell membrane

A

makes organism leaky
Antimicrobials can enter or cytoplasmic components can leave
Drugs work on dividing or static bacteria
Antifungals

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16
Q

Inhibit protein synthesis

A

some drugs enter the bacterium, combine with the ribosomes and disrupt normal protein production
Cell stops dividing or dies
Lincosamides, macrolides, tetracyclines, aminoglycosides

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17
Q

Interfere with critical enzymes or bind with intermediate compounds the bacteria need

A

bacterium is unable to function

Sulfonamide antibiotics

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18
Q

Impair production of bacterial nucleic acids (RNA and DNA):

A

bacterium or fungus is unable to divide; may be unable to produce critical proteins
May also attack mammalian DNA!*
Inability to reproduce, fetal abnormalities, or death
Some antifungals can cause fetal abnormalities
Quinolones work at sites on the pathogen’s nucleic acid that are not found in mammalian cells

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19
Q

Penicillins

A

Only effective against actively dividing bacteria*
Mostly gram pos and some neg
Don’t use with bacteriostatic drug!**

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20
Q

Penicillin is effective against

A 
Most gram (+) and some gram (-) bacteria
Bactericidal
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21
Q

Bactericidal

A

Block enzymes essential for cell wall assembly

Different enzymes are involved 🡪 different penicillins affect different enzymes

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22
Q

Penicillin Pharmacokinetics

A 
Well-absorbed from GIT and injection sites (except pen-G = inj only)
Hydrophilic .: does not reach therapeutic levels in the eye, brain or prostate
Excreted unchanged by kidneys – also actively transported into urine .: can attain much higher       [   ] in urine than blood
Many gram (-) bacteria are resistant to penicillins EXCEPT at the high [   ] in the urinary tract
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23
Q

Penicillin Cross-resistance

A

If bacteria become resistant to one type of penicillin, it is also resistant to most other penicillins

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24
Q

β-lactamase

A

Some bacteria, esp Staphylococci, acquire resistance by producing an enzyme, β-lactamase**** that attacks a part of the penicillin molecule: the β-lactam ring
A penicillin can sometimes be combined with another compound to produce a modified penicillin that is resistant to the β-lactamase enzyme
Clavulanic acid plus amoxicillin = Clavamox® (veterinary) or Augmentin® (human)
Packaged individually in foil 🡪 clavulanate absorbs moisture from air

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25
Penicillin Precautions
Hypersensitivity reactions are most common adverse reaction*** If allergic to one, is likely to be allergic to others Cross-reactivity**** May destroy beneficial GIT bacteria allowing pathogenic bacteria to proliferate Superinfection**** Can result in severe diarrhea and death in some species: guinea pigs, ferrets, hamsters, rabbits, snakes, birds, turtles and chinchillas Observe withdrawal times in food animals Penicillins are readily available to food animal producers
26
Cephalosporins
β-lactam antibiotic Disrupts cell wall synthesis Classified by generations according to when they were first developed
27
Cephalosporin 1st Generation
``` = gram (+) bacteria (Strep and Staph) Cefadroxil (Cefa-Tabs® and Cefa-Drops®) Cephalothin (Keflin®) Cephalexin (Keflex®) Cefazolin ```
28
Cephalosporin 2nd Generation
gram (-) bacteria
29
Cephalosporin 3rd Generation
``` = gram (+) & (-) bacteria (most are inj) Cefpodoxime (Simplicef®) - oral Cefovecin sodium (Convenia®) - SQ ```
30
Cephalosporins | MOA
β-lactam antibiotics; bactericidal similar to penicillins affecting cell walls Do not cross BBB Does cross placenta and can pass into milk [ ] in urine is high like penicillins
31
Cephalosporin Precautions
Hypersensitivity, but much lower than with penicillins Superinfection with oral administration of 1st –generation drugs May cause anorexia, V/D Don’t use with bacteriostatic drugs
32
Cefpodoxime proxetil
``` Simplicef Prodrug Active metabolite is cefpodoxime Oral adm Sid Tx Staph, Strep, Proteus, E. coli, Pasteurella ```
33
Cefovecin sodium
``` Convenia Reconstitute Refrigerate SQ adm Duration 7-14 days Tx Staph, Strep, Pasteurella Skin infections shelf life 56 days ```
34
VTNE Question of the Day: Why are most antibiotics contraindicated in rabbits and hamsters? A - Highly sensitive to renal toxicityB - Disrupts gram positive gut floraC - Their little hearts just can't take itD - Highly permeable blood-brain barrier
B - Disrupts gram positive gut flora
35
Aminoglycosides
Used to Tx serious bacterial infections Gentamicin, amikacin, neomycin, streptomycin, kanamycin, tobramycin, netilmicin Cross-resistance is not as common as with penicillins
36
Aminoglycosides MOA
bactericidal via action on ribosomal protein production; actively transported thru cell membrane into bacterium by an oxygen-dependent mechanism .: highly-effective against aerobic bacteria but not anaerobes Cell wall-inhibiting antibiotics like penicillins enhance the ability of aminoglycosides to enter and kill bacteria*
37
Aminoglycosides Pharmacokinetics
usually parenteral due to limited GIT absorption Hydrophilic .: do not cross BBB or into eye nephro- and ototoxicity***** with large or frequent doses. Cats Can cross placenta and cause harm to fetus Eliminated in kidneys – most of drug is excreted in urine
38
Quinolones / Fluoroquinolones
floxacin suffix Bactericidal 1st one in late 1980s = Enrofloxacin (Baytril®) Since then: marbofloxacin (Zeniquin®), orbifloxacin (Orbax®), difloxacin (Dicural®) All approved for dogs and cats except difloxacin (dogs only) Human drug = Ciprofloxacin
39
Quinolones / Fluoroquinolones MOA
interferes with DNA gyrase, preventing bacterial DNA supercoiling Effective against common gram (-) and gram (+) bacteria in skin, resp, and urinary infections Activity against Pseudomonas is superior to aminoglycosides Not recommended for streptococcal infections Ineffective against anaerobes
40
Quinolones / Fluoroquinolones Pharmacokinetics
Tx prostate infections**** | Up to ¼ of enrofloxacin is metabolized to ciprofloxacin***
41
Quinolones / Fluoroquinolones Precautions
Absorption is greatly reduced with antacids or sucralfate May lower seizure threshold Exceeding label dose in cats may lead to changes in retina and blindness!*** Should be reserved for more severe infections to minimize development of resistance!****
42
Tetracyclines
Bacteriostatic 🡪 need functional immune system! Most commonly used drugs for rickettsial dz (Rocky Mt spotted fever, salmon poisoning in dogs, hemobartonella), Mycoplasma pneumonia, chlamydial infections (ocular in cats), psittacosis in birds, and borreliosis (Lyme dz). Sometimes helps tear staining in dogs
43
Tetracyclines Older drugs
hydrophilic | Tetracycline and oxytetracycline
44
Tetracyclines Newer drugs
more lipophilic | Doxycycline and minocycline 🡪 longer half-life, broader spectrum of action, better penetration of tissues
45
Salmon Poisoning
DZ is caused by a rickettsial organism, Neorickettsia helminthoeca, which infects the parasite, Nanophyetus salmincola, a fluke Salmon, trout, Pacific giant salamander
46
Tetracyclines MOA
bind to ribosomes and disrupt protein synthesis 🡪 inhibit bacterial function
47
Tetracyclines Pharmacokinetics
Doxy- & minocycline are more lipophilic .: orally absorbed much better Tetracycline & oxytetracycline are readily CHELATED in the gut by mineral divalent cations Doxycycline’s absorption is only reduced by 20% Oxytetracyline = most commonly used INJECTABLE tetracycline Distributed to most tissues High [ ] in saliva and bronchial secretions Hydrophilic 🡪 no significant [ ] in CNS; can’t penetrate mammalian cells to reach intracellular pathogens Lipophilic 🡪 cross BBB, can enter eye and prostate Well-absorbed IM Excretion Tetracycline/oxytetracycline 🡪 primarily renal .: decrease dose with renal DZ; excreted by liver into intestines – some then chelated, some reabsorbed ENTEROHEPATIC CIRCULATION*** Doxycycline mostly excreted into the intestine
48
divalent cations
Ca++ = dairy products***** Mg++ = oral antacids; kaolin, pectin (Kaopectate); bismuth subsalicylate (Pepto-Bismol) Fe++ = iron supplements Cu++
49
Tetracyclines Precautions
Chelation with Ca++ 🡪 discolors adult teeth***** (mottled yellow) if tetracycline is given during their development; at high doses may slow bone development Superinfections in GIT following PO adm Cattle 🡪 Rumin stasis Dogs 🡪 GIT mucosal irritation 🡪 V/D, anorexia Cats 🡪 fever, depression, abd pain Horses 🡪 especially sensitive to rapid IV injection of doxycycline causing arrhythmias, collapse and death (chelation of Ca++?) Bacteriostatic 🡪 interfere with penicillins and cephalosporins******* Expired tetracycline/oxytetracycline decompose to a nephrotoxic compound 🡪 Fanconi’s syndrome
50
VTNE Question of the Day: Which drug family is associated with tooth enamel problems? A - AminoglycosidesB - QuinolonesC - MacrolidesD - TetracyclinesE - Cephalosporins
D - Tetracyclines
51
VTNE Question of the Day: A parrot is presented with psittacosis, to be treated with IM oxytetracycline at 100mg/kg, every 2-3 days for 30 days. If the parrot weighs 500 grams and the concentration of the drug is 100mg/ml, how many milliliters are necessary for a single dose?A - 0.05 milliliterB - 5 millilitersC - 0.5 milliliterD - 1.5 millilitersE - 90 milliliters
C - 0.5 milliliter
52
Sulfonamides
First antimicrobials to have widespread use .: many strains of bacteria are resistant May be combined with other drugs to make them bactericidal vs –static & increase efficacy Common sulfonamides used in vet med Sulfadimethoxine (Albon®)*****
53
VTNE Question of the Day: Which drug family is most associated with nephrotoxicity (kidney damage) as an adverse effect? A - Sulfonamides B - AminoglycosidesC - PenicillinsD - LincosamidesE - Cephalosporins
B - Aminoglycosides
54
Parasitism
When one species lives at the expense of another
55
Ectoparasite
Parasites on the outside of the body | fleas & ticks  “infested”
56
Endoparasite
Parasites on the inside of the body | heartworms  “infected”
57
Definitive host
contains adult stage (sexually mature)
58
Intermediate host
contains immature stage | Some parasites have >1 intermediate host
59
Zoonotic potential
Toxoplasma gondii Ancylostoma caninum = hookworm Toxocara canis  visceral larval migrans (VLM)
60
VLM
visceral larval migrans
61
Fenbendazole
Panacur GI Tract parasites (Toxocara Canis) Antinematodal Benzimidazole
62
Pyrantel pamoate
Nemex®, Strongid-T® Antinematodal Tetrahydropyrimidines Clinical uses: ascarids, strongyli, pinworms, hookworms
63
Imidazothiazoles
Febantel | Dogs and cats: hooks, rounds, whips
64
Avermectins
Antinematodal Dosage forms: Ivermectin (Heartgard®, Ivomec®)********** Moxidectin (ProHeart®, Quest Equine Oral Gel®) Doramectin Clinical uses: lots of bugs, esp in large animals  read pg 265-267 Other agents: Drontal Plus® (praziquantel/pyrantel pamoate/febantel)  tapes, hooks, rounds and whips in dogs
65
Anticestodal
tapeworms Bunamidine (Scoloban®) Epsiprantel (Cestex®) Praziquantel (Droncit®)*****
66
Antitrematodal
liver and lung flukes Praziquantel (Droncit®)***** Tapes and lung flukes in dogs and cats
67
Antiprotozoal
Drugs for Txing coccidia & other protozoans Sulfadimethoxine (Albon®)  dogs, cats, chickens and turkeys Many other drugs for livestock and poultry Drugs for Txing Giardia Metronidazole (Flagyl®)  dogs and cats Drugs for preventing Giardia
68
Heartworm Disease
Dogs and wild canids – also cats & ferrets Dirofilaria immitis vs Dipetalonema reconditum Adulticides Melarsomine dihydrochloride (Immiticide®)******** Arsenic compound  deep IM inj in lumbar region Microfilaricides Given 3-4 weeks after adulticide Ivermectin and milbemycin  extralabel use!
69
Heartworm Disease Preventatives
Ivermectin (Heartgard® products) Milbemycin oxime (Interceptor®, Sentinel®) Moxidectin (ProHeart®) Selamectin (Revolution®)
70
-cidal
Kills | Cidal drugs kill outright
71
–static
prevents replication | Static drugs depend more on a functioning immune system

Pharmacology Vet Tech (4 decks)

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