apramycin. some strains of s. aureus can also inactivate amikacin by phosphorylating it. pharmacokinetics amikacin is not absorbed orally and thus must be administered parenterally. it reaches peak serum concentrations in 0.5–2 hours when administered intramuscularly. less than 11% of the amikacin actually binds to plasma proteins. it is distributed into the heart, gallbladder, lungs, and bones, as well as in bile, sputum, interstitial fluid, pleural fluid, and synovial fluids. it is usually found at low concentrations in the cerebrospinal fluid, except when administered intraventricularly. in infants, amikacin is normally found at 10–20% of plasma levels in the spinal fluid, but the amount reaches 50% in cases of meningitis. it does not easily cross the blood–brain barrier or enter ocular tissue. while the half-life of amikacin is normally two hours, it is 50 hours in those with end-stage renal disease. the majority (95%) of amikacin from an intramuscular or intravenous dose is secreted unchanged via glomerular filtration and into the urine within 24 hours. factors that cause amikacin to be excreted via urine include its relatively low molecular weight, high water solubility, and unmetabolized state. chemistry amikacin is derived from kanamycin a: the synthesis of amikacin veterinary uses while amikacin is only fda-approved for use in dogs and for intrauterine infection in horses, it is one of the most common aminoglycosides used in veterinary medicine, and has been used in dogs, cats, guinea pigs, chinchillas, hamsters, rats, mice, prairie dogs, cattle, birds, snakes, turtles and tortoises, crocodilians, bullfrogs, and fish. it is often used for respiratory infections in snakes, bacterial shell disease in turtles, and sinusitis in macaws. it is generally contraindicated in rabbits and hares (though it has still been used) because it harms the balance of intestinal microflora. in dogs and cats, amikacin is commonly used as a topical antibiotic for ear infections and for corneal ulcers, especially those that are caused by pseudomonas aeruginosa. the ears are often cleaned before administering the medication, since pus and cellular debris lessen the activity of amikacin. amikacin is administered to the eye when prepared as an ophthalmic ointment or solution, or when injected subconjunctivally. amikacin in the eye can be accompanied by cephazolin. despite its use there amikacin (and all aminoglycosides) are toxic to intraocular structures. in horses, amikacin is fda-approved for uterine infections (such as endometriosis and pyometra) when caused by susceptible bacteria. it is also used in topical medication for the eyes and arthroscopic lavage; when combined with a cephalosporin, is used to treat subcutaneous infections that are caused by staphylococcus. for infections in the limbs or joints, it is often administered with a cephalosporin via limb perfusion directly into the limb or injected into the joint. amikacin is also injected into the joints with the anti-arthritic medication adequan in order to prevent infection. side effects in animals include nephrotoxicity, ototoxicity, and allergic reactions at im injection sites. cats tend to be more sensitive to the vestibular damage caused by ototoxicity. less frequent side effects include neuromuscular blockade, facial edema, and peripheral neuropathy. the half-life in most animals is one to two hours. treating overdoses of amikacin requires kidney dialysis or peritoneal dialysis, which reduce serum concentrations of amikacin, and/or penicillins, some of which can form complexes with amikacin that deactivate it.