... their various ring structures, the quinolones have a number of common functional groups that are essential for their antimicrobial activity. In addition, various modifications have produced compounds with differing physical, chemical, pharmacokinetic, and antimicrobial properties. For example, substitution at position 6 with a fluorine moiety markedly enhances activity against both gram-negative and gram-positive bacteria, as well as mycoplasmas and chlamydiae. These so-called fluoroquinolones, which are generally the most efficacious within each class, include enrofloxacin, norfloxacin, ciprofloxacin, orbifloxacin, ofloxacin, danofloxacin, flumequine, difloxacin, marbofloxacin, and other newer drugs. In addition, substitution with a piperazine ring at position 7 significantly increases tissue and bacterial penetration with consequent enhancement of activity; substitution with an oxygen atom at position 8 improves activity against gram-positive and anaerobic organisms without affecting the bactericidal profile. The quinolones are amphoteric and, with a few exceptions, generally exhibit poor water solubility between pH 6 and 8. In concentrated acidic urine, such as may be found in dogs and cats, some quinolones form needle-shaped crystals. Liquid formulations of various quinolones ...

... MIC 4 g / mL ), but is much less active against Staphylococcus and has variable activity against Proteus (MIC 0.5-16 g / mL). Due to instability of desfuroylceftiofur, microbiology services use a ceftiofur disk when performing susceptibility testing, so a false expectation of therapeutic efficacy may result for some pathogens. Pseudomonas, enterococci, and Enterobacter are resistant to ceftiofur and desfuroylceftiofur. Ceftiofur is associated with a duration and dose-related thrombocytopenia and anemia in dogs, which would not be expected with the recommended dosage regimen. Enrofloxacin, orbifloxacin, difloxacin, and marbofloxacin are all fluoroquinolones approved for UTI in dogs; although all are used in cats, only some are approved for this use. The fluoroquinolones are bactericidal, amphoteric drugs. They possess acidic and basic properties but are very lipid soluble at physiologic pH (pH 6.0-8.0) and thus have a high volume of distribution. All fluoroquinolone drugs usually have excellent activity against staphylococci and gram-negative bacteria, but may have variable activity against streptococci and enterococci. The therapeutic advantages of these drugs are their gram-negative antimicrobial activity and high degree of ...

... Ingredients, Chemotherapeutic Agents) toxicity Dicamba poisoning Table: Dicamba Table: Dichlobenil Dichlorometaxylenol Table: Dichlorprop Dichlorvos (Organophosphates, Mechanisms of Action, Chemotherapeutic Agents, Organophosphates, Active Chemical Ingredients, Chemotherapeutic Agents) toxicity Diclofop poisoning Table: Diclosulam Dicloxacillin Table: Dicrocoeliasis Dicrocoelium dendriticum Dicumarol poisoning Dicyclanil Dieldrin toxicity Dieldrin Diesel fuel poisoning Diestrus cytology Dietary abomasal impaction indigestion ruminal Diethylcarbamazine Diethylpropion Diethylstilbestrol (Urinary Incontinence, Systemic Pharmacotherapeutics of the Reproductive System: Introduction, Steroid Hormones, Urinary Incontinence) poisoning Table: Difenzoquat (methylsulfate) Diffuse fibrosing alveolitis pneumonia Difloxacin (Table: Dose Rates of Quinolones, Antimicrobial Therapy) Diflubenzuron Table: Diflufenzopyr Digestive system disorders introduction pharmacotherapeutics (The Monogastric Digestive System: Overview, Systemic Pharmacotherapeutics of the Digestive System: Introduction, The Ruminant Digestive System: Overview, The Monogastric Digestive System: Overview) Digitalis (Cardiac Glycosides, Management) Digital dermatitis cattle Digitoxin Digoxin Dihydrostreptomycin Dihydrotachsterol Diiodohydroxyquin Dilatation-volvulus gastric Dilatation esophagus small animals Dilated cardiomyopathy ferrets idiopathic Dilated pores of Winer Dilated cardiomyopathy Diltiazem (Calcium Channel Blockers, Class IV Drugs) Dimenhydrinate (Antihistamines, Drugs to Control or ...