Sulfonamides Flashcards
(4 cards)
Sulfa-/Trimethoprim
Potentiated Sulfonamide Antimicrobial
Combination antimicrobial agent used to treat bacterial and protozoal infections
Sulfonamides are bacteriostatic agents, while trimethoprim is bactericidal; both agents are time-dependent antibiotics. When used in combination, the resulting potentiated sulfonamides are bactericidal. Potentiated sulfonamides sequentially inhibit enzymes in the folic acid pathway, inhibiting bacterial thymidine synthesis. Sulfonamides compete with para-aminobenzoic acid (PABA) to reduce bacterial dihydrofolic acid (DFA) formation, and trimethoprim blocks the conversion of DFA to tetrahydrofolic acid by preferentially inhibiting bacterial dihydrofolate reductase. Infected tissue and cellular debris can inhibit the activity of sulfa-/trimethoprim by secreting PABA and thymidine.
Potentiated sulfonamides have a fairly broad spectrum of activity. Generally susceptible gram-positive bacteria include most streptococci and staphylococci and Nocardia spp. Many gram-negative organisms of the Enterobacteriaceae family are inherently susceptible to potentiated sulfonamides, but acquired resistance can occur. Sulfa-/trimethoprim is ineffective against Pseudomonas aeruginosa. Some protozoa (ie, Pneumocystis spp, Coccidia spp, Neospora spp, Toxoplasma spp) are also inhibited. Potentiated sulfonamides appear to have little activity against most atypical bacteria and anaerobes; methicillin-resistant staphylococci are usually resistant. Enterococcus spp infections may appear to be susceptible to sulfonamide-containing antibiotics in vitro; however, they are intrinsically resistant, so sulfa-/trimethoprim should not be used for these bacteria.
Resistance development is thought to occur more slowly to the combination of drugs than to either drug alone. In gram-negative organisms, sulfamethoxazole resistance is usually plasmid mediated, although a point mutation for dihydropteroate synthase also may confer resistance.
Contraindications include hypersensitivity to sulfonamides and severe renal or hepatic impairment.
Use with caution in patients with renal or hepatic insufficiency, patients with or at risk for uroliths, and in dog breeds predisposed to sulfonamide hypersensitivity (eg, Doberman pinschers).
Adverse effects in dogs include keratoconjunctivitis sicca, hypersensitivity, acute neutrophilic hepatitis with icterus, vomiting, anorexia, diarrhea, fever, hemolytic anemia, urticaria, polyarthritis, facial swelling, polydipsia, crystalluria, hematuria, polyuria, cholestasis, hypothyroidism, anemia, agranulocytosis, and idiosyncratic hepatic necrosis. May increase risk for acute pancreatitis. Mucocutaneous ulceration consistent with Stevens-Johnson syndrome has been reported.
Adverse effects in cats include anorexia, crystalluria, hematuria, leukopenia, and anemia.
Local injection adverse effects (eg, warmth, edema, pain) are possible.
Sulfa-/trimethoprim is potentially teratogenic; weigh the risks versus the benefits before prescribing.
Sulfasalazine
Sulfonamide/Salicylate Antibacterial/Immunosuppressive
cleaved into sulfapyridine and 5-aminosalicylic acid (5-ASA, mesalamine) by colonic bacteria. Although the exact mechanism of action for its therapeutic effects in treating colitis in small animal species has not been determined, it is believed that mesalamine’s local (not systemic) anti-inflammatory activity, including cyclooxygenase and lipoxygenase inhibition, provides the main therapeutic effect. Its antibacterial (sulfapyridine) and/or immunomodulatory activity may contribute to controlling clinical signs and course of the disease. In humans, concentrations of both metabolites in the colon are higher than by giving them orally as separate agents.
Sulfa-analogue that has GI antibacterial and anti-inflammatory activity used for inflammatory bowel disease; has also been used for vasculitis
Contraindications include hypersensitivity to sulfasalazine, sulfas, or salicylates; intestinal or urinary obstructions; and Dobermans.
Use with caution in cats and in patients that have liver, renal, or hematologic diseases
Adverse effects in dogs include keratoconjunctivitis sicca (KCS), anorexia, vomiting, cholestatic jaundice, hemolytic anemia, leukopenia, vomiting, decreased sperm counts, and allergic dermatitis.
Adverse effects in cats include anorexia, vomiting, anemia.
Sulfadimethoxine
Sulfonamide Antimicrobial
Approved to treat bacterial and protozoal infections in small and large animal species
time-dependent, bacteriostatic agents when used alone, but are considered bactericidal when used in combination with dihydrofolate reductase inhibitors (eg, ormetoprim, trimethoprim; ie, potentiated sulfonamides). Sulfonamides prevent bacterial replication by competing with para-aminobenzoic acid (PABA) in the biosynthesis of tetrahydrofolic acid in the pathway to form folic acid. Only microorganisms that synthesize their own folic acid are affected by sulfonamides.
Gram-positive bacteria that are generally susceptible to sulfonamides include some strains of streptococci, staphylococcus, Bacillus anthracis, Clostridium perfringens, Clostridium tetani, and many strains of Nocardia spp. Sulfonamides also have in vitro activity against some gram-negative species, including some strains of Enterobacter spp, Escherichia coli, Klebsiella spp, Pasteurella spp, Proteus spp, Salmonella spp, and Shigella spp. Sulfonamides have activity against some protozoa (eg, Coccidia spp, Toxoplasma spp). Sulfonamides are inactive against atypical bacterial (eg, Chlamydia spp, Mycoplasma spp, rickettsial), viral, or fungal infections.
Sulfonamides are less efficacious in purulent exudate, necrotic tissue, or areas with extensive cellular debris.
Contraindications include hypersensitivity to sulfonamides and severe renal or hepatic impairment.
Use with caution in animals with mild-to-moderate hepatic disease or if the animal has (or a history of) immune-mediated disease.
Use with caution in breeds that are prone to sulfonamide hypersensitivity (ie, Doberman pinschers, Samoyeds, miniature schnauzers).
Adverse effects in dogs include keratoconjunctivitis sicca (KCS), hypersensitivity reactions (eg, rashes, fever, myelosuppression, immune-mediated hemolytic anemia, immune-mediated thrombocytopenia, dermatitis, nonseptic polyarthritis), hepatopathy, hepatic necrosis, focal retinitis, and vomiting. Diminished renal or hepatic function or urinary obstruction may occur.
Potentially teratogenic; weigh risks versus benefits.
Sulfadimethoxine/Ormetoprim
Potentiated Sulfonamide Antimicrobial
Potentiated sulfa similar to sulfa-/trimethoprim but may have fewer adverse effects and is labeled for once daily administration. Used for the treatment of skin and soft tissue infections in dogs.
shares mechanism of action and (probably) the bacterial spectrum of activity with sulfa-/trimethoprim. Sulfonamides are bacteriostatic agents. When used in combination with either ormetoprim or trimethoprim, the resulting potentiated sulfonamides are bactericidal. Combining sulfonamides and dihydrofolate reductase inhibitors (eg, ormetoprim, trimethoprim) results in synergistic antimicrobial effects.1 Potentiated sulfonamides sequentially inhibit enzymes in the folic acid pathway, inhibiting bacterial thymidine synthesis. The sulfonamide competes with para-aminobenzoic acid (PABA) to reduce bacterial dihydrofolic acid (DFA) formation, and ormetoprim blocks the conversion of DFA to tetrahydrofolic acid by preferentially inhibiting bacterial dihydrofolate reductase.
Potentiated sulfonamides have a fairly broad spectrum of activity. Generally susceptible gram-positive bacteria include most streptococci, many strains of staphylococcus, and Nocardia spp. Although many gram-negative organisms of the Enterobacteriaceae family are susceptible to potentiated sulfonamides, this does not include Pseudomonas aeruginosa. Some protozoa (ie, Pneumocystis jiroveci, Coccidia spp, Toxoplasma spp, Neospora spp) are also inhibited by the combination. Potentiated sulfonamides appear to have little activity against most atypical bacteria and anaerobes; methicillin-resistant staphylococci are usually resistant. Enterococcus infections may appear to be susceptible to sulfonamide-containing antibiotics in vitro; however, they are intrinsically resistant, so sulfonamide-containing antibiotics should not be used for these bacteria.
Resistance development is thought to occur more slowly to the combination of drugs than to either drug alone. In gram-negative organisms, sulfamethoxazole resistance is usually plasmid mediated, although a point mutation for dihydropteroate synthase also may confer resistance.
Contraindications include hypersensitivity to sulfonamides, thiazides, or sulfonylurea agents; severe renal or hepatic impairment; and Doberman pinschers.
Caution is advised in diminished renal or hepatic function, urinary obstruction, and urolithiasis.
Adverse effects in dogs include keratoconjunctivitis sicca (KCS), hypersensitivity reactions (type 1 or type 3), acute neutrophilic hepatitis with icterus, vomiting, anorexia, diarrhea, fever, hemolytic anemia, urticaria, polyarthritis, facial swelling, polydipsia, crystalluria, hematuria, polyuria, cholestasis, hypothyroidism, anemia, agranulocytosis, and idiosyncratic hepatic necrosis.
Sulfadimethoxine/Ormetoprim is potentially teratogenic; weigh the risks versus the benefits before prescribing.
