AMINOGLYCOSIDES

1. AMINOGLYCOSIDES • -Used with serious gram negative bacterial infections • -suffix –micin or –mycin (exception: amikacin) • NOTE: Lincosamides and Macrolides use tetracyclines use –mycin for generic names as well. Tetracyclines use –mycin for their trade names. • amikacin • Injection • gentamicin • Topical, injectable • neomycin • Topical, oral

2. AMINOGLYCOSIDES • -Bactericidal by targeting the ability of bacteria’s ribosomes to assemble proteins • -Aminoglycosides must be inside the bacterial cell to produce its effects and oxygen must be present for Aminoglycosides to enter • Ineffective against anaerobic bacteria and in areas lacking oxygen (colon, deep puncture wounds) • The concurrent use of cell-wall inhibiting antibiotics enhances the ability of Aminoglycosides to enter • -Once daily dosing is safest

3. AMINOGLYCOSIDES -Absorbed well through skin that is not intact. • -Pyogenic infections limit the action of Aminoglycosides as the medication will bind to the debris instead of the body’s cells. Clean wound first. • NEPHROTOXOCITY and OTOTOXICITY are side effects of normal, high, or frequent doses as Aminoglycosides accumulate in the kidneys and inner ear (this can also be true for fetuses as they easily cross the placenta) • Nephrotoxicity may be reversible if the drug is reduced /withdrawn before there is necrosis in the tubules • Accumulation in the inner ear can cause deafness • Ototoxicity can also affect balance

4. FLUOROQUINOLONES (QUINOLONES) • -Most have –floxacin as a suffix • enrofloxacin (Baytril) • Used in small and large animals • ciprofloxacin (Cipro) • Used in small and large animals • marbofloxacin (Zeniquin) • Used in small animals • orbifloxacin (Orbax) • Used in small animals

5. QUINOLONE MECHANISM OF ACTION • -Interfere with bacterial DNA which must be tightly coiled. Quinolones attack the bacteria's enzyme gyrase whose role is to supercoil. • -Bactericidal • -Effective against common gram negative and positive bacteria (except Strep) • -Used for skin, urinary, and respiratory infections -Absorbed better when administered orally in small animals and by injection in large animals

6. FLUOROQUINOLONES • -Can cause bubble-like lesions in rapidly growing canine cartilage. Degenerate and arthritic changes can arise as adults • Relatively contraindicated In growing animals • -High doses in cats can cause changes in the retina, leading to blindness • -Reserve for serious infections as bacterial resistance is a problem -Fluoroquinolones cannot be used extra-label on food animals

7. TETRACYCLINES -cycline suffix -Used in large and small animals • -Used to TX: RMSF, Potomac horse fever, Lyme Disease, Leptospirosis, Wolbachia, Chlamydia, Mycoplasma • -Older tetracyclines: tetracycline and oxytetracycline, newer tetracyclines: doxycycline, minocycline

8. TETRACYCLINES -Bacteriostatic • -Bind to bacterial ribosomes and prevent t-RNA from attaching. This stops protein synthesis. • Inhibit cellular function and division, but does not immediately destroy bacteria. • Rely on the body having a functional immune system since they are bacteriostatic

9. TETRACYCLINE PRECAUTIONS • Older tetracyclines chelate calcium in developing teeth and bones • Dentin and enamel formation can be disrupted and a yellow discoloration may develop • Bone development can be slowed if calcium is chelated

10. TETRACYCLINE PRECAUTIONS • GI upset may be seen with oral administration • Normal flora in rumen can be killed off causing rumen inactivity • Irritation of GI mucosa in dogs causing V/D, anorexia • Cats are susceptible to esophageal stricture- chase with a few tsp water • DO NOT GIVE IV TO HORSES • Arrythmias, collapse, and death • Give slowly IV to other species

11. SULFONAMIDES • AKA Sulfa drugs • Resistance is seen because of overuse • Commonly used sulfa drugs: • sulfadimethoxine (Albon, combined with ormetoprim in Primor) • sulfadiazine (combined with trimethoprim in Tribrissen) • sulfasalazine (Azulfidine, used in GI)

12. SULFONAMIDES • Often POTENTIATED to increase efficacy and make them bactericidal (otherwise BACTERIOSTATIC) • trimethoprim and ormetoprim • Sulfonamides block an enzyme needed for bacteria to create folic acid. Potentiators block different enzymes, but still ones that are required for folic acid production. When sulfas are potentiated, the compound is BACTERICIDAL. • Broad spectrum: many G+ and G- bacteria, coccidia, and Toxopasma • Often used for UTIs.

13. SULFONAMIDES • 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.

14. LINCOSAMIDES • clindamycin (Antirobe), lincomycin (Lincosin) • 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

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

16. METRONIDAZOLE • AKA Flagyl • Bactericidal, possibly by effecting DNA synthesis • Effective against protozoa, including Giardia and Trichomonas. Good for treating infections in bowel or deep wounds. • Neurological side effects can be seen with high doses or prolonged treatment.

17. CHLORAMPHENICOL • 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

18. 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.

19. ANTIFUNGALS 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