indication

For the treatment of tuberculosis. May also be used in combination with other drugs to treat tularemia (Francisella tularensis), plague (Yersia pestis), severe M. avium complex, brucellosis, and enterococcal endocarditis (e.g. E. faecalis, E. faecium).

pharmacology

Streptomycin 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.

mechanism of action

Aminoglycosides like Streptomycin "irreversibly" bind to specific 30S-subunit proteins and 16S rRNA. Specifically Streptomycin binds to four nucleotides of 16S rRNA and a single amino acid of protein S12. This interferes with decoding site in the vicinity of nucleotide 1400 in 16S rRNA of 30S subunit. This region interacts with the wobble base in the anticodon of tRNA. This leads to interference with the initiation complex, misreading of mRNA so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and the breakup of polysomes into nonfunctional monosomes.

toxicity

Nephrotoxic and ototoxic potential. Nephrotoxicity is caused by accumulation of the drug in proximal renal tubular cells, which results in cellular damage. Tubular cells may regenerate despite continued exposure and nephrotoxicity is usually mild and reversible. Streptomycin is the least nephrotoxic of the aminoglycosides owing to the small number of cationic amino groups in its structure. Otoxocity occurs via drug accumulation in the endolymph and perilymph of the inner ear. Accumulation causes irreversible damage to hair cells of the cochlea or summit of the ampullar cristae of the vestibular complex. High frequency hearing loss precedes low frequency hearing loss. Further toxicity may result in retrograde degeneration of the auditory nerve. Vestibular toxicity may result in vertigo, nausea and vomiting, dizziness and loss of balance. LD50=430 mg/kg (Orally in rats with Streptomycin Sulfate); Side effects include nausea, vomiting, and vertigo, paresthesia of face, rash, fever, urticaria, angioneurotic edema, and eosinophilia.

absorption

Rapidly absorbed after intramuscular injection with peak serum concentrations attained after 1 - 2 hours. Not absorbed in the GI tract.

half life

5 - 6 hours in adults with normal renal function

route of elimination

Small amounts are excreted in milk, saliva, and sweat. Streptomycin is excreted by glomerular filtration.

drug interactions

Bumetanide: Increased ototoxicity

Cefotaxime: Increased risk of nephrotoxicity

Cefotetan: Increased risk of nephrotoxicity

Cefoxitin: Increased risk of nephrotoxicity

Ceftazidime: Increased risk of nephrotoxicity

Ceftriaxone: Increased risk of nephrotoxicity

Colistimethate: Aminoglycosides may enhance the nephrotoxic effect of Colistimethate. Aminoglycosides may enhance the neuromuscular-blocking effect of Colistimethate. Due to the potential for additive or synergistic toxicities (including both nephrotoxicity and neuromuscular blockade) between colistimethate and the aminoglycoside antibiotics, this combination should be avoided whenever possible. If these agents must be used together, patients' renal and neuromuscular function should be monitored closely.

Ethacrynic acid: Increased ototoxicity

Furosemide: Increased ototoxicity

Tacrolimus: Additive renal impairment may occur during concomitant therapy with aminoglycosides such as Streptomycin. Use caution during concomitant therapy.

Ticarcillin: Ticarcillin may reduce the serum concentration of Streptomycin. Ticarcillin may inactivate Streptomycin in vitro and the two agents should not be administered simultaneously through the same IV line.