Therapeutic drug monitoring (TDM) of ribavirin is believed to be effective in predicting virological response and/or hematological side effects in patients with chronic hepatitis C undergoing peginterferon/ribavirin combination treatment.

In the present study, steady-state ribavirin levels were retrospectively analyzed in serum samples from patients at week 12 of combination therapy with peginterferon alfa-2a (Pegasys) and ribavirin or peginterferon alfa-2b (Peg-Intron) and ribavirin.

Patients were classified as early virological responders on the basis of undetectable HCV-RNA or HCV-RNA drop 2 log from baseline at week 12.

The mean ribavirin level was not different between early virological responders (2.3 ± 0.1 µg/ml, n = 45) and early virological non-responders (2.0 ± 0.2 µg/ml, n = 10).

There was no correlation between ribavirin levels at week 12 and early virological response.

In patients with early virological response, hemoglobin (Hb) levels were found to be decreased by 18% on average from the baseline values; however, in only 2 patients did Hb levels decline below 100 g/l. There was a moderate negative correlation between ribavirin levels and Hb levels at week 12 (R = -0.50, p < 0.001); however, ribavirin levels did not correlate with relative or absolute decline in Hb as compared to baseline levels or with ribavirin dose per kilogram body weight.

In addition, a significant negative correlation between ribavirin levels and glomerular filtration rate was found (R = -0.31, p < 0.05).

In conclusion, the authors write, “Based on our results, monitoring of ribavirin serum levels at week 12 of HCV combination therapy does not appear to predict early virological response or reductions in Hb levels.”

“Further research is needed to assess their diagnostic value at other time points of peginterferon/ribavirin combination treatment and/or in patients with renal insufficiency.”

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Is the Antiviral Effect of Ribavirin in Humans Mediated by Mutagenic Properties?  - 05/03/04

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03/31/06

Reference
J Donnerer, M Grahovac, E Stelzl and others. Ribavirin Levels and Haemoglobin Decline in Early Virological Responders and Non-Responders to Hepatitis C Virus Combination Therapy. Pharmacology 76:136-140. 2006.