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Foundations- Antibiotics > Inhibition of Nucleic Acid Synthesis of Intermediary Metabolism > Flashcards

Inhibition of Nucleic Acid Synthesis of Intermediary Metabolism Flashcards

1
Q

describe the tiers of sulfonamide and diaminopyrimidine antibiotics

A

sulfa-trim: first line/tier 1 in equine and companion animal exotics

sulfa or sulfa-potentiator prohibited from ELDU in adult lactating dairy cattle or dairy cattle >20 months: RESTRICTED

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2
Q

describe the mechanism of action of sulfonamide and diaminopyrimidine antibiotics

A

inhibits folate synthesis pathway in bacteria (folate in an important co-factor for pyrimidines, purines, methionine, and other amino acids)

ultimately inhibits nucleic acid synthesis!

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3
Q

describe prototype and others of sulfonamide and diaminopyrimidine antibiotics

A

sulfamethoxazole (+trimethoprim)

sulfadiazine (+trimethoprim)

sulfadimethoxine (Albon)

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4
Q

describe spectrum of activity of sulfonamide and diaminopyrimidine antibiotics

A
  1. time dependent
  2. bacterioSTATIC: if just sulfas alone
  3. bacteriCIDAL: potentiated sulfas + trimethoprim
  4. broad spectrum: gram +, -, aerobes, anaerobes (not great tho), protozoa, coccidia
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5
Q

describe route of administration of sulfonamide and diaminopyrimidine antibiotics

A

orally or IV

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6
Q

describe dispotision of sulfonamide and diaminopyrimidine antibiotics

A
  1. moderately lipophilic
  2. inefficient in purulent material
  3. renal excretion/hepatic metabolism
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7
Q

describe toxicity of sulfonamide and diaminopyrimidine antibiotics

A
  1. KCS: keratoconjunctivitis sicca in dogs
  2. hepatic necrosis in dogs
  3. hypothyroidism in dogs
  4. bone marrow suppression (neutropenia)
  5. pyremethamine overdose: myeloid suppression, laminitis
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8
Q

describe specific indications and contraindications of sulfonamide and diaminopyrimidine antibiotics

A

specific indications
1. UTI: sulfa-trim
2. pneumocytsis jirovecii (carinii)
3. cost effective oral option for horses

contraindications
1. often avoided entirely or used as a last resort in dogs

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9
Q

describe tiers of fluroquinolone antibiotics

A

1st gen, nalidixic acid: tier 1 for companion animal and exotic

2nd gen enrofloxacin, marbofloxacin: tier 2

enrofloxacin/danofloxacin: RESTRICTED in food producing animals

3rd gen pradofloxacin: labeled for cats in US

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10
Q

describe mechanism of action of fluroquinolones

A

inhibits nucleic acid synthesis by inhibiting DNA gyrase (topoisomerase II) and topoisomerase IV

does NOT affect mammalian topoisomerases! = no side effects to host cells

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11
Q

describe the prototype and others of fluoroquinolones

A

1st gen: nalidixic acid

2nd gen:
-ciprofloxacin
-enrofloxacin
-marbofloxacin
-orbifloxacin
-danofloxacin

3rd gen:
-levofloxacin
-pradofloxacin

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12
Q

describe spectrum of activity of fluoroquinolones

A
  1. AUC:MIC; once daily dosing
  2. bacteriCIDAL
  3. narrow spectrum: gram -, +, and aerobes
    -atypical: mycoplasma, camplyobacter, leptospirosis, ureaplasma
    -pradofoxacin has the broadest activity: adds gram + and anaerobes BUT is NOT reliable against streptococcus
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13
Q

describe routes of administration of fluoroquinolones

A

IV, SQ

orally: small animal

ophthalmic

NOTE: caustic, vascular, perivascular reaction so stay in vein if giving IV!!

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14
Q

describe disposition of fluoroquinolones

A
  1. lipophilic: can access privileged sites like CNS
  2. high volume of distribution; low protein binding
  3. MIXED:
    -renal and HEPATIC (primary) metabolism- enterohepatic circulation
  4. ciprofloxacin: active hepatic metabolite of enrofloxacin BUT giving ciprofloxacin is NOT the same as giving enrofloxacin; generic cirpo is cheaper but less bioavailable
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15
Q

describe toxicity of fluoroquinolones

A
  1. retinal degeneration in cats! Baytril can blind cats in a dose dependent manner!!
  2. arthropathy in growing animals
  3. perivascular reaction: sloughing
  4. sporadic tendinopathy in horses
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16
Q

describe specific indications and contraindications of fluoroquinolones

A

specific indications:
1. for broad spectrum coverage (when anaerobes or strep not likely involved)
-in combination with narrow spectrum penicillin
2. meningitis and prostatitis (crosses BBB and BPB)
3. anaplasmosis in cattle (conditional)
4. swine and bovine respiratory disease

contraindications:
1. young growing animals (arthropathy)
2. monotherapy in equine respiratory disease
3. lactating dairy cattle >20 months: PROHIBITED
4. poultry: no ELDU, no labeled formation; ILLEGAL TO GIVE TURKEYS AND CHICKENS BAYTRIL

17
Q

describe the tiers of nitroimidazole antibiotics

A

metronidazole: first line/1st tier: companion animals

metronidaole and nitrofurans: PROHIBITED in food producing animals

18
Q

describe the mechanism of action of nitroimidazoles

A

interferes with nucleic acid synthesis by breaking DNA strands and inhibiting repair enzymes (DNAase1)
ONLY IN ANAEROBIC ENVIRONMENT

19
Q

describe prototype of nitroimidazoles

A

metronidazole

20
Q

describe spectrum of activity of nitroimidazoles

A
  1. bacteriCIDAL
  2. broad spectrum: ANAEROBES ONLY but gram + and gram -
    -weird ones: entamoeba hystolytica, giardia, balantidium coli, helicobacter pylori, and trichomonas
21
Q

describe route of administration of nitroimidazoles

A

orally, per rectum for higher doses, IV

22
Q

describe disposition of nitroimidazoles

A
  1. lipophilic
  2. high volume of distribution
  3. HEPATIC metabolism
23
Q

describe toxicity of nitroimidazoles

A
  1. inappetance when given orally to horses; can avoid by giving per rectum
  2. carcinogen to lab animals
  3. dose dependent neurologic (central)
24
Q

describe specific indications and contraindications of nitroimidazoles

A

specific indications:
1. anaerobic infections
2. clostridial diseases
3. hemorrhagic colitis
4. inflammatory bowel disease (inhibition of leukocyte endothelial adhesion in post capillary venules)

contraindications:
1. liver failure
2. neurologic disease; dose dependent
3. BANNED in food animal (bc was shown to be carcinogenic in lab animals)

25
Q

describe mechanism of action of nitrofuran antibiotics and prototype

A

interferes with nucleic acid synthesis via breakage of DNA strands

prototype: nutrofirantoin (oral), nitrofurazone (topical)

26
Q

describe disposition of nitrofurans

A
  1. rapidly eliminated through kidneys
  2. high concentrations in urine
  3. NOT systemically effective
27
Q

describe toxicity of nitrofurans

A

carcinogens that cause cancer in a dose dependent manner!!!!!!!

28
Q

describe specific indications and contraindications of nitrofurans

A

specific indications:
1. nitrofurantoin for acute or recurrent urinary tract infections in companion animals (poor absorption means excrete in urine = good for UTIs!!)

contraindications:
1. cross resistance in nitroimidazoles
2. BANNED in food animals (even topically!!)

29
Q

describe use of nitrofurazone

A

topical

BANNED IN FOOD PRODUCING SPECIES

carcinogenic: wear gloves when handling!!

broad spectrum: but not effective against pseudomonas aeruginosa

30
Q

describe tiers of rifamycin antibiotics

A

rifampin: tier 2, equine and food animal

31
Q

describe mechanism of action and prototype of rifamycins

A

MOA: inhibit protein synthesis via DNA dependent RNA polymerase blockade

prototype: rifampin

32
Q

describe spectrum of activity and route of administration of rifamycins

A

spectrum of activity:
1. time DEPENDENT (usually 2x daily)
2. bacteriCIDAL
3. narrow spectrum: gram + aerobe and anaerobes

route: oral

33
Q

describe disposition of rifamycins

A
  1. highly lipophilic
  2. hepatic metabolism
34
Q

describe toxicity of rifamycin antibiotics

A
  1. discoloration of bodily fluids:
    -red/orange tears, urine, saliva (harmless but warn the owner!)
  2. clinical hepatitis: hepatic enzyme activity increase
35
Q

describe specific indications and contraindications of rifamycins

A

specific indications:
1. rhodococcus equi (combo with macrolide)
2. added to other antimicrobial therapy for abscess and osteomyelitis

contraindications:
1. NEVER ADMINISTER AS MONOTHERAPY: rapid antimicrobial resistance

36
Q

describe how rifampin interacts with other drugs

A

potent inducer of microsomal enzymes in the liver resulting in clinically significant increased excretion of steroid drugs, ketoconazole, barbiturates, digoxin, omeprazole, and oral anticoagulants

Foundations- Antibiotics (3 decks)

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