Amikacin is a semi-synthetic aminoglycoside antibiotic derived from kanamycin A. Similar to other aminoglycosides, amikacin disrupts bacterial protein synthesis by binding to the 30S ribosome of susceptible organisms. Binding interferes with mRNA binding and tRNA acceptor sites leading to the production of non-functional or toxic peptides. Other mechanisms not fully understood may confer the bactericidal effects of amikacin. Amikacin is also nephrotoxic and ototoxic.
Indication
For short-term treatment of serious infections due to susceptible strains of Gram-negative bacteria, including Pseudomonas species, Escherichia coli, species of indole-positive and indole-negative Proteus, Providencia species, Klebsiella-Enterobacter-Serratia species, and Acinetobacter (Mima-Herellea) species. Amikacin may also be used to treat Mycobacterium avium and Mycobacterium tuberculosis infections.
Pharmacology
Amikacin is an aminoglycoside antibiotic. Aminoglycosides work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth. Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. In the past the aminoglycosides have been used in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects, particularly in endocarditis. Aminoglycosides are mostly ineffective against anaerobic bacteria, fungi and viruses.
Toxicity
Mild and reversible nephrotoxicity may be observed in 5 - 25% of patients. Amikacin accumulates in proximal renal tubular cells. Tubular cell regeneration occurs despite continued drug exposure. Toxicity usually occurs several days following initiation of therapy. May cause irreversible ototoxicity. Otoxocity appears to be correlated to cumulative lifetime exposure. Drug accumulation in the endolymph and perilymph of the inner ear causes irreversible damage to hair cells of the cochlea or summit of ampullar cristae in the vestibular complex. High frequency hearing is lost first with progression leading to loss of low frequency hearing. Further toxicity may lead to retrograde degeneration of the 8th cranial (vestibulocochlear) nerve. Vestibular toxicity may cause vertigo, nausea, vomiting, dizziness and loss of balance.
Affected Organisms
Enteric bacteria and other eubacteria
Absorption
Rapidly absorbed after intramuscular administration. Rapid absorption occurs from the peritoneum and pleura. Poor oral and topical absorption. Poorly absorbed from bladder irrigations and intrathecal administration.
Half Life
2-3 hours
Protein Binding
0-11%
Elimination
Amikacin is excreted primarily by glomerular filtration.
Distribution
* 24 L [normal adult subjects]
Clearance
* 100 mL/min
References
•
Edson RS, Terrell CL: The aminoglycosides. Mayo Clin Proc. 1999 May;74(5):519-28.
[Pubmed]
