Streptomycin

STREPTOMYCIN

Streptomycin (Figure 45–1) was isolated from a strain of Streptomyces griseus. The antimicrobial activity of streptomycin istypical of that of other aminoglycosides, as are the mechanisms of resistance. Resistance has emerged in most species, severely limit-ing the current usefulness of streptomycin, with the exceptions listed below. Ribosomal resistance to streptomycin develops read-ily, limiting its role as a single agent.

Clinical Uses

A. Mycobacterial Infections

Streptomycin is mainly used as a second-line agent for treatment of tuberculosis. The dosage is 0.5–1 g/d (7.5–15 mg/kg/d for children), which is given intramuscularly or intravenously. It should be used only in combination with other agents to prevent emergence of resistance.

B. Nontuberculous Infections

In plague, tularemia, and sometimes brucellosis, streptomycin, 1 g/d (15 mg/kg/d for children), is given intramuscularly in combina-tion with an oral tetracycline.

Penicillin plus streptomycin is effective for enterococcal endo-carditis and 2-week therapy of viridans streptococcal endocarditis. Gentamicin has largely replaced streptomycin for these indications. Streptomycin remains a useful agent for treating enterococcal infec-tions, however, because approximately 15% of enterococcal iso-lates that are resistant to gentamicin (and therefore resistant to netilmicin, tobramycin, and amikacin) will be susceptible to streptomycin.

Adverse Reactions

Fever, skin rashes, and other allergic manifestations may result from hypersensitivity to streptomycin. This occurs most fre-quently with prolonged contact with the drug either in patients who receive a prolonged course of treatment (eg, for tuberculosis) or in medical personnel who handle the drug. Desensitization is occasionally successful.

Pain at the injection site is common but usually not severe. The most serious toxic effect with streptomycin is disturbance of ves-tibular function—vertigo and loss of balance. The frequency and severity of this disturbance are in proportion to the age of the patient, the blood levels of the drug, and the duration of admin-istration. Vestibular dysfunction may follow a few weeks of unusu-ally high blood levels (eg, in individuals with impaired renal function) or months of relatively low blood levels. Vestibular tox-icity tends to be irreversible. Streptomycin given during pregnancy can cause deafness in the newborn and, therefore, is relatively contraindicated.