Drug Level Analysis in Viral Hepatitis
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Ribavirin and Tenofovir

Therapeutic Drug Monitoring (TDM) means monitoring of drug levels in the blood before, during or after drug treatment to help optimise drug dosing for the individual patient. TDM in HIV & Viral Hepatitis is used to optimise drug regimens for the individual patient by increasing efficacy and avoiding drug-related toxicity, and typically requires a clearly defined relationship between plasma concentration and pharmacological effect and/or toxicity for the drug. Situations calling for TDM include:
  • Significant inter- and intra-individual variability in plasma drug concentration at a fixed dose
  • A narrow therapeutic window, or index, i.e. the level at which they are effective is very close to the level at which they are toxic
  • A high toxicity profile (dose-limiting toxicity)
  • Drug-drug or drug-food interaction
  • Pediatric patients, pregnancy
  • Extremes of BMI
  • Complex clinical situations (e.g. liver impairment, drug interactions, treatment failure)
  • Suspected nonadherence
Lab21 offers TDM for ribavirin (HCV) and tenofovir (HIV and HBV), as well as for a wide range of HIV drugs. Lab21 TDM services are supported by highly respected experts in the area, Professor David Back and Professor Clive Loveday.

Ribavirin

As reviewed by Sauvage et al, 2009, Ribavirin has a large distribution volume, a long half-life and large inter-individual pharmacokinetic variability. Several studies suggest that there is a poor dose-concentration relationship for Ribavirin and that the concentration of the drug in the blood, rather than the dose, is associated with effectiveness of the therapy. Anemia may also be caused by ribavirin in a dose-dependent manner. Therefore, therapeutic drug monitoring of Ribavirin plasma concentrations can be useful for tailoring individual dosing, as well as for monitoring adherence.

Tenofovir

Tenofovir is a drug used to treat both HIV and HBV, and TDM for tenofovir is useful to monitor adherence to the drug regimen. It may also be useful for monitoring of drug levels in the plasma in e.g. complex clinical situations.

For HIV co-infection, view Liverpool HIV Pharmacology Group drug interactions web-site.

Please note that Lab21 is not responsible for the content of any external websites.

Reference
  1. Sauvage F-L, Stanke-Labesque F, Gagnieu M-C et al. Feasibility of ribavirin monitoring in Hepatitis C. Ther Drug Monit, 2009; 31(3): 374–381.
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