SULFONAMIDES & POTENTIATED SULFAS AKA Sulfa drugs, enteric sulfas, systemic sulfa Resistance is seen because of overuse Often potentiated to increase efficacy and make them bactericidal (otherwise Bacteriostatic) Trimethoprim and ormetoprim Commonly used sulfa drugs: Sulfadimethoxine (Albon, combined with ormetoprim in Primor) Sulfadiazine (combined with trimethoprim in Tribrissen Sulfamethoxazole (combined with trimethoprim in Septra- human drug) Sulfachlorpyridazine Sulfasalazine SULFONAMIDES & POTENTIATED SULFAS

MECHANISM OF ACTION and PHARMACOKINETICS BACTERIOSTATIC: organisms that make their own folic acid needed for protein and nucleic acid metabolism. Sulfonamides block an enzyme needed for this process. Potentiators block different enzymes, but still those that are required for folic acid. When combined, the compound is BACTERICIDAL. Broad spectrum: many G+ and G- bacteria, coccidian, and Toxopasma All but sulfasalazine are well absorbed from GI tract of monogastric animals. Lipophilic and able to cross the BBB Metabolized by liver, excreted by the kidneys, often used for UTIs. MECHANISM OF ACTION and PHARMACOKINETICS

Sulfonamides are known to produce keratoconjunctivitis sicca in dogs Sulfonamides are known to produce keratoconjunctivitis sicca in dogs. It is often not reversible. Skin reactions may be seen. Thrombocytopenia and Leukopenia in small animals can occur. Crystalluria can occur which can damage renal tubules and lead to renal failure. Carnivores are more likely than herbivores. Likeliness increases if dehydrated Oral sulfa can cause salivation in cats if tablet breaks in mouth. PRECAUTIONS FOR USE

Clindamycin (Antirobe), lincomycin (Lincosin), pirlimycin (Pirsue) Bacteriostatic or bactericidal by affecting protein synthesis. Action depends on concentration at infection site. Gram +, anaerobes, and Toxoplasma Contraindicated to use in horses, ruminants, hamsters, guinea pigs, rabbits. Can cause serious GI issues and death. Clindamycin is often used for dental infections, deep pyodermas, accesses, bite wounds, osteomyelitis LINCOSAMIDES

Erythromycin, azithromycin (Zithromax), tilmicosin (Micotil), tylosin (Tylan) Tylosin and tilmicosin are primarily used in cattle. Bacteriostatic by inhibiting protein synthesis Excreted in bile Stimulates intestinal motility so cramping is common Erythromycin can cause fatal diarrhea in horses MACROLIDES

METRONIDAZOLE AKA Flagyl Bactericidal, possibly by effecting DNA synthesis Effective against protozoa, including Giardia and Trichomonas. Not very effective against aerobic bacteria. Good for treating infections in bowel or deep wounds. Neurological side effects can be seen with high doses or prolonged treatment. METRONIDAZOLE

Low concentrations are bacteriostatic, high are bactericidal Disrupts protein synthesis Cannot be used in food animals Can cause aplastic anemia in humans Avoid inhaling powder, wash hands, wear gloves Use with caution in cats and neonates as the liver is unable to effectively metabolize the med Can inhibit the metabolism of phenobarbital if given simultaneously CHLORAMPHENICOL

GRISEOFULVIN: oral med used to treat dermatophytes (ringworm) Known for being teratogenic in cats. Do not use in pregnant animals. Use caution when handling if pregnant. AMPHOTERICIN B: IV med for deep or systemic infections Rapid onset of action Nephrotoxicity is extremely common and dose related. Monitor BUN and creatinine every time. AZOLES: oral (ketoconazole, itraconazole, and fluconazole) or topical (miconazole, clotrimazole) meds for deep or systemic infections Usually used before Amphotericin B because side effects are fewer Topical meds are used for dermatophytosis, topical yeast infections GI side effects are common with oral meds Hepatotoxicity is an issue with ketoconazole ALT is commonly elevated in many animals without causing concern ANTIFUNGALS