Kanamycin clinical pharmacology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Clinical Pharmacology
The drug is rapidly absorbed after intramuscular injection and peak serum levels are generally reached within approximately one hour. Doses of 7.5 mg/kg give mean peak levels of 22 mcg/mL. At 8 hours following a 7.5 mg/kg dose, mean serum levels are 3.2 mcg/mL. The serum half-life is 2 1/2 hours. Intravenous administration of kanamycin over a period of one hour resulted in serum concentrations similar to those obtained by intramuscular administration.
Kanamycin diffuses rapidly into most body fluids including synovial and peritoneal fluids and bile. Significant levels of the drug appear in cord blood and amniotic fluid following intramuscular administration to pregnant patients. Spinal fluid concentrations in normal infants are approximately 10 to 20 percent of serum levels and may reach 50 percent when the meninges are inflamed.
Studies in normal adult patients have shown only trace levels of kanamycin in spinal fluid. No data are available on adults with meningitis.
The drug is excreted almost entirely by glomerular filtration and is not reabsorbed by the renal tubules. Hence, high concentrations are attained in the nephron, and the urine may contain levels 10 to 20 times higher than those in serum. Little, if any, metabolic transformation occurs. Renal excretion is extremely rapid. In patients with normal renal function, approximately one-half of the administered dose is cleared within 4 hours and excretion is complete within 24 to 48 hours. Patients with impaired renal function or with diminished glomerular filtration pressure excrete kanamycin more slowly. Such patients may build up excessively high blood levels which greatly increase the risk of ototoxic reactions. In severely burned patients the half-life may be significantly decreased and resulting serum concentrations may be lower than anticipated from the mg per kg dose.[1]
References
Adapted from the FDA Package Insert.