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Pharmacology Final > Macrolides/Lincosamides and Sulfonamides > Flashcards

Macrolides/Lincosamides and Sulfonamides Flashcards

1
Q

macrolides MOA

A

protein synthesis inhibitor- irreversible binding to 50 S ribosome prevents protein synthesis

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2
Q

are macrolides bacteriostatic or bactericidal

A

generally bacteriostatic but can be -cidal at high concentrations

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3
Q

what characteristic do some macrolides possess that can be useful to treat certain difficult infections?

A

anti-biofilm activity: useful for infx that are hard to treat bc of biofilm formation

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4
Q

what other effects do macrolides have?

A

immunomodulatory effects independent of abx activity
inhibit infiltration of neutrophils into airway, inhibit production of pro-inflammatory cytokines

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5
Q

what effect do macrolides have on the GI tract in horses, dogs and cattle?

A

pro-kinetic: act as direct motilin receptor agonists

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6
Q

macrolides spectrum of activity

A

generally considered broad-spectrum
good activity against gram + aerobes, gram - aerobes, and some anaerobic bacteria

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7
Q

what bacteria are resistant to macrolides?

A

Enterobacteriaceae, Psuedomonas, Nocardia, Mycoplasma, Chlamydia, Mycobacterium

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8
Q

what is the representative drug for macrolides

A

erythromycin
new ones are azithrymycin, clarithromycin

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9
Q

what are the mechanisms of resistance against macrolides?

A
  1. rRNA methylation: prevents binding of drug to ribosome
  2. active drug efflux
  3. enzymatic inactivation (less common)
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10
Q

how are macrolides absorbed?

A

variable absorbed from GI tract if not inactivated by gastric acid. oral formulas are often enteric-coated

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11
Q

how are macrolides administered?

A

IV or IM administration leads to rapid absorption, but pain and swelling occurs at injection sites :(

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12
Q

where are macrolides distributed?

A

widely distributed in tissues EXCEPT those of CNS

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13
Q

where are macrolides NOT distributed to?

A

CNS!

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14
Q

metabolism and excretion of macrolides is ______ dependent

A

drug dependent: some undergo hepatic metabolism and biliary excretion (erythromycin, tiamulin), others are excreted unchanged in bile and urine (tylosin, tilmicosin)

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15
Q

what macrolides inhibit cytochrome P450 enzymes?

A

erythromycin and tiamulin

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16
Q

adverse effects of macrolides

A
  • incidence is relatively low
  • all are irritants and cause severe pain with IM inj
  • dose-related GI disturbances in most animals
  • GI effects can be life-threatening in horses!
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17
Q

how can macrolides lead to death in horses?

A

erythromycin in horses can lead to Clostridium overgrowth, leading to serious D+ illness/death

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18
Q

what macrolide can produce cardiac toxicity in species other than cattle and swine?

A

tilmicosin
- fatal after IV inj in humans
- calcium channel blockade

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19
Q

drug of choice for Campylobacter D+ or abortion

A

erythromycin

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20
Q

what is erythromycin often used for?

A
  • drug of choice for Campy D+ or abortion
  • penicillin-alternative in pen sensitive animals
  • less effective alternative to clindamycin or metronidazole in anaerobic infx
  • ampicillin or amoxicillin alternative in txt of lepto
  • tetracycline alternative for rickettsial infx
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21
Q

what is tylosin used for

A

local and systemic infx caused by mycoplasmas, Gm+, anaerobes and some respiratory Gm- pathogens

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22
Q

what is tilmicosin used for

A

used only in cattle injectably and swine medicated feed for respiratory disease

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23
Q

what is tiamulin used for

A

used in swine for control and txt of swine dysentery (Brachyspira hyodysenteriae) and mycoplasmal arthritis

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24
Q

what is clarithromycin used for

A

drug of choice for treating Rhodococcus equi when combined with Rifampin

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25
what is the drug of choice for treating Rhodococcus equi?
Clarithromycin + Rifampin
26
what is Tulathromycin?
Draxxin!!
27
what type of drug is Draxxin
macrolide
28
what is tulathromycin (draxxin) used for
long-acting, single-dose macrolide for respiratory disease in cattle and swine. drug accumulates in lung tissue
29
lincosamides
from Lincoln, NE! - clindamycin, lincomycin, pirlimycin
30
are macrolides bacteriostatic or bactericidal?
can be either depending on drug concentration, bacterial species, and inoculum/amount of bacteria
31
lincosamides MOA
inhibition of protein synthesis: binds to the 50S ribosomal subunit (same site as macrolides) and inhibits peptidyl transferase
32
what do lincosamides have activity against
Gram + aerobes, mycoplasma, and anaerobes
33
distribution of lincosamides
widely distributed, excellent penetration of bone and soft tissues, including tendon sheaths. CNS levels are low extensive metabolism in liver
34
how are lincosamides excreted?
excreted in urine, bile, and feces
35
what species are lincosamides contraindicated in? why?
horses, rabbits, hamsters and guinea pigs - may produce severe, often fatal necrotizing enterocolitis (clostridial overgrowth) - oral administration to ruminants can be fatal
36
what toxicities can occur with lincosamides?
- necrotizing enterocolitis! - salmonellosis in dogs - neuromuscular blockage at high doses or when administered with anesthetics
37
what drugs cause necrotizing enterocolitis in horses, rabbits, hamsters and guinea pigs?
lincosamides
38
what is clindamycin used for?
dogs and cats for periodontal disease, osteomyelitis, dermatitis, and deep soft tissue infections also used for toxoplasmosis in dogs and cats
39
what is lincomycin used for?
used in swine for swine dysentery, staph, strep, and mycoplasma infx
40
what is pirlimycin used for?
udder infusion for the txt of bovine mastitis caused by gram + cocci
41
sulfonamides, diaminopyrimidines and their combos
Sulfonamides are derivatives of sulfanilamide and the substitutions on the molecule account for differences in potency, spectrum of activity and some PK properties.
42
MOA of sulfonamides
interfere with synthesis of folic acid inhibits formation of pteroic acid thru inhibition of dihydropterate synthase (DHPS) by acting as a false substrate/competitive inhibitor
43
what are sulfonamides competing with for the enzyme dihydropteroate synthetase?
PABA: para-aminobenzoic acid
44
how can action of sulfonamides be reversed?
excess of PABA; because they are competing and can overcome sulfa activity tissue exudates and necrotic tissue should be removed before treatment with sulfas
45
are sulfonamides bacteriostatic or bactericidal?
bacteriostatic
46
sulfonamide activity is against
broad spectrum, inhibits growth of bacteria and protoza like toxoplasma and coccidia
47
why aren't sulfonamides good as single agents?
there has been extensive resistance that has developed :(
48
why are sulfonamides selective to killing microorganisms?
animal cells take up pre-formed folic acid and thus don't need to synthesize dihydrofolate/folic acid. folic acid is required for purine biosynthesis
49
what bacteria are sulfonamides good against?
Bacillus spp, Brucella spp, Listeria, Nocardia, pyogenic Streptococcus spp, Cryptosporidium spp, Chlamidia and Chlamydophila spp, Pneumocystis, Coccidia remain susceptible.
50
what bacteria are resistant to sulfonamides?
Mycobacterium spp, Mycoplasma spp, Psuedomonas.
51
how have bacteria become so resistant to sulfonamides?
production of an insensitive dihydropteroate enzyme or hyperproduction of PABA, which antagonizes the sulfonamide - there is complete cross-resistance for sulfonamides - extensive resistance likely reflects the extensive use of these drugs over many years
52
what are unique pharmacokinetic properties of sulfonamides?
- widely distributes to tissues including CNS - very insoluble in water, can precipitate out and form crystals in acidic environments: urine! - combinations are used
53
what drug can form crystals in acidic environments like urine?
sulfonamides
54
how are sulfonamides metabolised?
primarily thru acetylation, with some glucoronidation and hydroxylation
55
why are dogs less likely to get crystalluria from sulfonamides?
dogs are deficient in acetylatoin and don't form the acetylated metabolites. the metabolites are less soluble in urine and increase risk of crystalluria whereas glucoronide conjugates are highly water-soluble and rapidly excreted
56
how are sulfonamides excreted?
urinary excretion via GFR, active tubular excretion and passive reabsorption
57
what species is deficient in N-Acetylation, leading to less risk of toxicity from sulfonamides?
canines
58
most common adverse effects of sulfonamides
- urinary tract: crystalluria, hematuria, obstruction - hematopoetic disorders: thrombocytopenia, anemia - derm rxns: topic epidermal necrolysis - KCS: keratoconjuctivitis sicca
59
what odd toxicity do sulfonamides have?
idiosyncratic drug rxns in animals and humans, 10 days to 3 weeks after exposure hypersensitivity rxn or "drug fever"
60
what drugs cause a hypersensitivity reaction or "drug fever" in dogs?
sulfonamides
61
what breed has a severe reaction to sulfa drugs?
doberman pinschers- avoid giving these drugs?
61
what does hypersensitivity reaction "drug fever" present as?
fever, arthropathy, epistaxis, hepatopathy, KCS, uveitis, skin eruptions of various types - may be due to toxic metabolites- genetic component?
62
what drugs do you want to avoid giving to doberman pinschers?
63
sulfonamides have severe rxns in what breeds?
dobies
64
how do you typically dose sulfonamides?
initiate therapy with a "priming dose" and then give maintenance doses that are 1/2 of the priming dose at intervals that are equal to the half life of the drug
65
how should you administer sulfonamides?
IV! because of alkalinity of parenteral formulas
66
what are indications for use of sulfonamides?
toxoplasmosis, chlamydiosis, chronic colitis respiratory, genitourinary and soft tissue infxns are common indications
67
how are diaminopyrimadines different than sulfonamides?
they interfere with folic acid production like sulfonamides, but via a different mechanism: they inhibit dihydrofolate reductase (DFR) enzyme
68
why are diaminopyrimidines and sulfonamides often used together?
they inhibit sequential steps in the folic acid production pathway = synergistic activity individually they are bacteriostatic, together are bactericidal
69
trimethoprim is what kind of drug?
diaminopyrimadine almost always used in combo w sulfonamides
70
diaminopyrimadines
trimethoprim, ormetoprim, pyrimethamine by themselves have fairly broad spectrum of activity almost exclusively given in combo w sulfonamides
71
potentiated sulfonamides
sulfonamide + trimethoprin combinations are bactericidal and synergistic
72
what is the formulation of potentiated sulfonamides?
usually in ratio of 1:5 trimethoprin:sulfonamide 1:20 ratio is optimal, but is much lower bc of rapid excretion of trimethoprin
73
rifampin MOA
inhibition of RNA synthesis by binding the B-subunit of DNA-dependent RNA polymerases
74
adverse effects of rifampin
liver and GI. monitor liver enzymes in dogs!
75
rifampin is good for treating what?
intracellular bacteria like Mycobacterium (tuberculosis) - active in Gm+ bacteria and intracellular penetration - effective against Staph, Rhodo, and MRSA
76
why are combinations of rifampin commonly used?
a single mutation of the amino sequence of the Beta subunit can lead to resistance
77
treatment of choice for Rhodococcus equi in foals
rifampin
78
oxazolidinones
super important for methicillin-resistant Staph and resistant enterococci!
79
MOA of oxazolidinones
blocks protein synthesis: binds to site on 23S ribosomal RNA of 50S subunit
80
how often are oxazolidinones used
- adverse effects not reported - used to be expensive, but generic forms have lowered cost - should be used sparingly based on susceptibility testing, not rec'd for routine use
81
what drug should NOT be used with sulfonamides?
methenamine: forms insoluble precipitates
82
methenamine should not be given with what drugs? why?
sulfonamides: forms insoluble precipitates
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Pharmacology Final (9 decks)

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