Liver Function Monitoring with Vancomycin and Piperacillin/Tazobactam Therapy

Introduction to Liver Function Monitoring

For patients with normal baseline liver function, routine monitoring is not required unless symptoms develop, as recommended by the Infectious Diseases Society of America 1
Baseline liver function tests should be obtained before initiating therapy with vancomycin or piperacillin/tazobactam, according to the American Association for the Study of Liver Diseases 2

For patients with pre-existing liver disease, more frequent monitoring is warranted, with monitoring recommended weekly for two weeks, then every two weeks for the first two months, as suggested by the European Association for the Study of the Liver 4
If AST/ALT is less than 2 times the upper limit of normal, repeat liver function tests in 2 weeks, and if levels are decreasing, further tests are only needed for symptoms, as recommended by the American College of Gastroenterology 4
If AST/ALT is 2-5 times the upper limit of normal, monitor weekly for two weeks, then every two weeks until normal, and consider dose adjustment or alternative antibiotics if levels continue to rise, according to the Infectious Diseases Society of America 4

For mild elevations without symptoms, continue therapy with close monitoring, as recommended by the American Association for the Study of Liver Diseases 3
For moderate elevations, consider risk-benefit assessment of continuing therapy, and for severe elevations (>5 times upper limit of normal) or if symptoms of liver injury develop, consider discontinuation of the antibiotics, as suggested by the European Association for the Study of the Liver 2
Consider alternative antibiotics with less hepatotoxic potential, and monitor liver function every 2-3 days until improvement begins, according to the American College of Gastroenterology 3

Be aware of potential interactions with other hepatotoxic medications, and consider the additive risk when combining multiple potentially hepatotoxic agents, as recommended by the American College of Clinical Pharmacy 4
Don't assume that all AST elevations are due to the antibiotics; consider other causes including the infection itself, and don't discontinue necessary antibiotics prematurely for mild, asymptomatic elevations in liver enzymes, as suggested by the Infectious Diseases Society of America 1