Vancomycin has complex pharmacokinetics. I can recall a case where I saw oral vancomycin for cellulitis. The likely causative organism of the cellulitis was MRSA. This patient was fairly complex and hospitalized for a few days.
Upon hospitalization, the patient was assessed and eventually put on Vancomycin. The dose was 1,ooo mg every 24 hours. The patient was responding and showed dramatic improvement within a couple days. Upon discharge the attending physician wrote an order for oral vancomycin 250mg four times daily.
Upon investigation, the only diagnosis this patient had was the cellulitis. If we remember the pharmacokinetics of vancomycin, oral vancomycin is poorly absorbed. Remembering basic pharmacokinetics, an IV medication is 100% bioavailable. Basically this means the drug entirely makes it the blood stream (by definition, the drug hits the blood stream instantaneously when given intravenously). If a medication is poorly absorbed through the GI tract, like vancomycin, its bioavailability is comparatively low.
This low bioavailability of oral vancomycin makes it very unlikely that treatment of a systemic infection or an infection not in the GI tract will be successful. Oral vancomycin is commonly utilized for C. Diff infections.
The order in this case for oral vancomycin would be inappropriate due to this fact, and this put the patient at risk for reinfection, or an inadequately treated infection. There are other factors that go into medication selection, but a couple of oral alternatives that have MRSA coverage would be clindamycin or Bactrim.
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