Ribavirin (Copegus, Rebetol, Virazole) can be used in combination with PEGylated interferon alpha to treat hepatitis C infection. There is accumulating evidence that monitoring of ribavirin for TDM purposes may be useful. For example, a tentative therapeutic range is emerging, together with data that suggests inter-individual variation in ribavirin pharmacokinetics. Measurement may therefore be useful to verify adherence, prevent toxicity, and minimise side effects. Other indications for possible measurement include drug-drug interactions, especially in HIV co-infected patients, and post-transplant when immunosuppressant drugs are prescribed. In the latter case, it is also vital to monitor immunosuppressant concentrations.
|Turnaround:||The assay is performed monthly, but subject to demand or urgency may be run weekly.
Please contact the laboratory for advice.
0.5 mL EDTA anticoagulated plasma, taken at least 6 hours post-dose.
IMPORTANT: the plasma MUST be separated into its own sample vial no longer than 90 minutes after phlebotomy. Failure to comply will produce misleading results. Ribavirin concentrations are relatively stable in plasma, but the sample should be dispatched promptly by first class mail, or courier
|Method:||Liquid chromatography-tandem mass spectrometry|
|Principle:||Ribavirin is measured in plasma (or serum) using a validated in-house liquid chromatography-mass spectrometry (LC-MS/MS) method|
|Turnaround: 4 weeks|
|Price: Contact Lab|
|IDM service: kch-tr.KCHIDMService@nhs.net|
|Therapeutic Ranges: (males = females)|
|A definitive target range in therapy has not been established for ribavirin in the treatment of hepatitis C. However, favourable outcomes have been associated with plasma ribavirin greater than 1.5 mg/L at week 4 of therapy, whilst the risk of serious side effects is associated with plasma concentrations greater than 4.5 mg/L.|