KANAMYCIN

Kanamycin A is an antibiotic complex produced by Streptomyces kanamyceticus Okami & Umezawa from Japanese soil. Comprised of three components, kanamycin A, the major component, and kanamycins B and C, two minor congeners. Antibacterial.

Kanamycin, O-3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)-O-[6-deoxy- 6-amino-α-D-glucopyranosyl-(1→4)]–2-deoxy-D-streptamine (32.4.6), is isolated from a culture fluid of the actinomycete Streptomyces kanamyceticus, which produces three antibiotics—kanamycins A, B, and C.
Kanamycin A is similar to streptomycin and neomycines, and it possesses a broad spectrum of antimicrobial action. It is active with respect to most Gram-positive and Gramnegative microorganisms (staphylococci, colon bacillus, klebisella, Fridlender’s bacillus, proteus, shigella, salmonella).
It is used to treat sepsis, meningitis, osteomyelitis, peritonitis, pneumonia, pyelonephritis, pyelocystitis, infected wounds, and post-operational, purulent complications that are caused by microorganisms sensitive to this drug. Kanamycin is used to treat tuberculosis of the lungs and other organs upon resistance to other antituberculosis drugs. Synonyms of this drug are karmycin, kamaxin, resistomycin, and many others.

It is active against staphylococci, including methicillin-resistant strains. Other aerobic and anaerobic Gram-positive cocci and most Gram-positive rods are resistant, but M. tuberculosis is susceptible. It is widely active against most aerobic Gram-negative rods, except Burkholderia cepacia and Sten. maltophilia. Treponema pallidum, Leptospira and Mycoplasma spp. are all resistant.

Resistance is usually plasmid borne and due to enzymatic inactivation of the drug by enzymes that also inactivate gentamicin or tobramycin . Resistance due to reduced permeability is also encountered.

C_max 500 mg intramuscular： c.15–20 mg/L after 1 h
Plasma half-life: 2.5 h
Volume of distribution: 0.3 L/kg
Plasma protein binding: Low
Absorption and distribution
Very little is absorbed from the intestinal tract. The peak plasma concentration in the neonate is dose related: concentrations of 8–30 mg/L (mean 18 mg/L) have been found 1 h after a 10 mg/kg dose. The drug is confined to the extracellular fluid. The concentration in serous fluids is said to equal that in the plasma, but it does not enter the CSF in therapeutically useful concentrations even in the presence of meningeal inflammation.
Excretion
It is excreted almost entirely by the kidneys, almost exclusively in the glomerular filtrate. Up to 80% of the dose appears unchanged in the urine over the first 24 h, producing concentrations around 100–500 mg/L. It is retained in proportion to reduction in renal function. Less than 1% of the dose appears in the bile. In patients receiving 500 mg intramuscularly preoperatively, concentrations of 2–23 mg/L have been found in bile and 8–14 mg/kg in gallbladder wall.

Formerly used for severe infection with susceptible organisms, it has largely been superseded by other aminoglycosides.

Intramuscular injections are moderately painful, and minor side effects similar to those encountered with streptomycin have been described. Eosinophilia in the absence of other manifestations of allergy occurs in up to 10% of patients. Other manifestations of hypersensitivity are rare.
As with other aminoglycosides, the most important toxic effects are on the eighth nerve and much less frequently on the kidney. Renal damage is seen principally in patients with pre-existing renal disease or treated concurrently or sequentially with other potentially nephrotoxic agents. The drug accumulates in the renal cortex, producing cloudy swelling, which may progress to acute necrosis of proximal tubular cells with oliguric renal failure. Less dramatic deterioration of renal function, particularly exaggeration of the potential nephrotoxicity of other drugs or of existing renal disease, is of principal importance because it increases the likelihood of ototoxicity.
Vestibular damage is uncommon but may be severe and prolonged. Hearing damage is usually bilateral, and typically affects frequencies above the conversational range. Acute toxicity is most likely in patients in whom the plasma concentration exceeds 30 mg/L, but chronic toxicity may be seen in patients treated with the drug over long periods. Auditory toxicity may be potentiated by concurrent treatment with potent diuretics like ethacrynic acid. If tinnitus – which usually heralds the onset of auditory injury – develops, the drug should be withdrawn.
Neuromuscular blockade is seen particularly in patients receiving other muscle relaxants or suffering from myasthenia gravis and may be reversed by neostigmine.