Generally speaking oral vancomycin is very well tolerated. The oral form of the drug is not absorbed, so is only used for certain infections of the gut, which the vancomycin will treat as it passes through the gut unabsorbed. When used for this indication, the usual dose is to take it four times per day, and it is not OK to take it as a single daily dose. Oral vancomycin is never effective for other infections and if vancomycin is need for another infection, it must be provided intravenously for the full course of treatment. Many of the frightening side effects listed for vancomycin are due to the intravenous form of the drug. The most common side effects from the oral form of the drug is nausea, vomiting, and an unpleasant taste. It is also possible to have an allergic reaction. The only mechanism by which the oral form of vancomycin can affect the liver is as part of an allergic reaction, and this is not common. It is more likely that the liver test abnormalities are related to the underlying infection that requires treatment, unless the patient is having other evidence of an allergic reaction. If there is concern that the vancomycin has contributed to the liver test abnormalities, then he should be checked by his physician to see if there is other evidence of an allergic reaction. Otherwise, it would be appropriate to complete the course of treatment.