SULFONAMIDES & POTENTIATED SULFAS

MECHANISM OF ACTION and PHARMACOKINETICS

oBACTERIOSTATIC: 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.

oBroad spectrum: many G+ and G- bacteria, coccidian, and Toxopasma

oAll but sulfasalazine are well absorbed from GI tract of monogastric animals.

oLipophilic and able to cross the BBB

oMetabolized by liver, excreted by the kidneys, often used for UTIs.

PRECAUTIONS FOR USE

oSulfonamides are known to produce keratoconjunctivitis sicca in dogs. It is often not reversible.

oSkin reactions may be seen.

oThrombocytopenia and Leukopenia in small animals can occur.

oCrystalluria can occur which can damage renal tubules and lead to renal failure.o Carnivores are more likely than herbivores.o Likeliness increases if dehydrated

oOral sulfa can cause salivation in cats if tablet breaks in mouth.

LINCOSAMIDES

oClindamycin (Antirobe), lincomycin (Lincosin), pirlimycin (Pirsue)

oBacteriostatic or bactericidal by affecting protein synthesis. Action depends on concentration at infection site.

oGram +, anaerobes, and Toxoplasma

oContraindicated to use in horses, ruminants, hamsters, guinea pigs, rabbits. Can cause serious GI issues and death.

oClindamycin is often used for dental infections, deep pyodermas, accesses, bite wounds, osteomyelitis

MACROLIDES

oErythromycin, azithromycin (Zithromax), tilmicosin (Micotil), tylosin (Tylan)

oTylosin and tilmicosin are primarily used in cattle.

oBacteriostatic by inhibiting protein synthesis

oExcreted in bile

oStimulates intestinal motility so cramping is common

oErythromycin can cause fatal diarrhea in horses

METRONIDAZOLE

oAKA Flagyl

oBactericidal, possibly by effecting DNA synthesis

oEffective against protozoa, including Giardia and Trichomonas. Not very effective against aerobic bacteria. Good for treating infections in bowel or deep wounds.

oNeurological side effects can be seen with high doses or prolonged treatment.

CHLORAMPHENICOL

oLow concentrations are bacteriostatic, high are bactericidalo Disrupts protein synthesis

oCannot be used in food animals

oCan cause aplastic anemia in humanso Avoid inhaling powder, wash hands, wear gloves

oUse with caution in cats and neonates as the liver is unable to effectively metabolize the med

oCan inhibit the metabolism of phenobarbital if given simultaneously

ANTIFUNGALS

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