Folic Acid Inhibitors

Question 1

Short acting sulfonamides

Answer 1

Sulfacetamide
Sulfamethizole
Sulfathiazole

Sulfisoxazole

Sulfachlorpyridazine

Question 2

Which short-acting sulfonamide is good for opthalmic and topic preparations? Why?

Answer 2

Sulfacetamide (neutral pH)

Question 3

Which short-acting sulfonamide is good for UTIs in small animals? Why?

Answer 3

Sulfisoxazole (very soluble and rapidly excreted)

Question 4

Which short-acting sulfonamide is good for respiratory and enteric infections in youngsters (calves, swine)?

Answer 4

Sulfachlorpyridazine

Question 5

If you wanted to give a short-acting sulfonamide to a calf with enteric infection, what would you give?

Answer 5

Sulfachlorpyridazine in the form of Vetisulid IV injection

Question 6

Which short-acting sulfonamide is safe in youngsters?

Answer 6

Sulfachlorpyridazine

Question 7

Intermediate acting sulfonamides

Answer 7

Sulfamethoxazole
Sulfapyridine

Sulfamethazine/sulfadimidine
Sulfadiazine

Question 8

Which intermediate lasting sulfonamides is used for UTIs in small animals

Answer 8

Sulfamethoxazole

Question 9

Which two sulfonamides are used to treat UTIs in small animals

Answer 9

Sulfasoxazole

Sulfamethoxazole

Question 10

Which intermeidate acting sulfonamide is used for prophylactics in drinking water/feed

Answer 10

Sulfamethazine/sulfadimidine

Question 11

Which intermediate acting sulfonamide is released from a sulfasilazine group?

Answer 11

Sulfapyridine

Question 12

Long acting sulfonamides

Answer 12

Sulfadimethoxine
Sulfamethazine

Sulfaethoxypyridazine

Question 13

Enteric sulfonamides

Answer 13

Succinylsulfathiazole

Sulfasalazine
Sulfaquinoxaline
Sulfaguanidine

Phthalylsulfathiazole

Question 14

Topical sulfonamides

Answer 14

Silver sulfadiazine

Mafenide

Question 15

Important feature of enteric sulfonamides

Answer 15

Low solubility - poor absorption into systemic circulation.

Good for local action in GIT

Question 16

Which sulfonamide is used for colitis in dogs

Answer 16

Sulfasalazine

Question 17

Which sulfonamide is used for coccidiosis in poultry

Answer 17

Sulfaquinoxaline

Question 18

Immunological toxicity of sulphonamides (2)

Answer 18

1. Keratoconjunctivitis sicca (pyridine ring induces hypersensitivity on lacrimal acinar cells)
2. Hepatic necrosis (slow acetylation increases production of Hydroxylamine metabolites which are hepatotoxic)

Question 19

Non-immunological toxicity of sulphonamides (2)

Answer 19

1. Nephrotoxicity (due to crystalluria post acetylation. Prevention = hydration, sodium bicarb, vegetarian diet)
2. Blood dyscrasias
   a. hypothrombinemia
   b. aplastic anemia
   c. thrombocytopenia

(changes in cell count. Sulfaquinoxoline inhibits vit K epoxide reductase – no vit K, no hepatic clotting factors)

Question 20

T/F - Non-immunological toxicity of sulphonamides is reversible

Answer 20

Yes!

Blood dyscrasias is reversible by giving Vit K

Question 21

Which dog breed is sensitive to sulphonamides? What are the sensitivities?

Answer 21

Doberman Pinschers

Polyarthritis
Fever
Cutaneous eruptions
Hepatitis

Question 22

What can occur in dogs and ducks due to sulphonamide sensitivity

Answer 22

Hypoglycemia

Question 23

What can potentiated sulfas cause in dogs? Is this reversible?

Answer 23

Iatrogenic hypothyroidism

Targets thyroid peroxidase which synthesizes thyroxine (very reversible)

Question 24

How do sulphonamides become resistant? (2)

Answer 24

Chromosomal mediated resistance (slow)

Plasmid mediated resistance (fast)

Question 25

What are three consequences of sulphonamide resistance

Answer 25

1. Impaired drug penetration 2. Increased PABA production 3. Sulfonamide resistant dihydropteroate synthase

Question 26

What is the efficacy predictor of sulphonamides

Answer 26

Type II (time dependent)

Question 27

MOA diaminopyrimidines

Answer 27

Reversibly binds/inhibits dihydrofolate (DHF) reductase in bacteria only (doesnt affect human enzyme)

Question 28

Which diaminopyrimidine is specific for protozoa

Answer 28

Pyrimethamine

Question 29

Diamminopyrimidines (6)

Answer 29

'TOP MAT' Trimethoprim Ormetoprim Pyrimethamine Metioprim Aditoprim Tetroxoprim

Question 30

T/F Potentiated sulfonamides are bacteristatic

Answer 30

No, CIDAL

Question 31

Potentiated sulfonamides (5)

Answer 31

1. Sulfadiazine + Trimethoprim 2. Sulfadoxine + Trimethoprim 3. Sulfamethoxazole . Trimethoprim 4. Sulfadimethoxine + Ormetoprim 5. Sulfaquinoxaline + Pyrimethamine

Question 32

Which potentiated sulfa is used for horses

Answer 32

Sulfadiazine + Trimethoprim

Question 33

Which potentiated sulfa is for cows/pigs

Answer 33

Sulfadoxine + Trimethoprim

Question 34

Which potentiated sulfa is for dogs

Answer 34

Sulfadimethoxine + Ormetoprim

Question 35

Which potentiated sulfa is best for coccidiosis (and other protozoal infections)

Answer 35

Sulfaquinoxalne + Pyrimethamine

Question 36

Which antimicrobial class is best for aerobic gram+/gram- and protozoal infections

Answer 36

Potentiated sulfas

Question 37

How are potentiated sulfas metabolized

Answer 37

Liver: - Sulfonamides (acetylation, glucuronation) - Diaminopyrimidines (oxidation and hydroxylation)

Question 38

T/F potentiated sulfas are well distributed

Answer 38

True - pass into CSF, placenta, milk...