Nine of the 11 patients were in the pegIFN-ribavirin arm. The mean interval between the outset of anti-HCV treatment and the diagnosis of symptomatic mitochondrial toxicity was 26.5 weeks (±13.4).
The clinical manifestations of symptomatic hyperlactatemia were general weakness (5 patients), weight loss (5 patients; ≥6 kg in 4 cases), nausea (2 patients), severe rapid-onset lipoatrophy (2 patients), dyspnea (1 patient), and peripheral neuropathy (1 patient). No intercurrent acute health disorders were diagnosed. Five patients had hyperlactatemia (>3 mM; ≥5 mM in 2 cases). Two patients (lactate level unknown in 1) had evidence of metabolic acidosis (bicarbonate levels 15 and 16 mM). In patients with pancreatitis, the main symptoms of pancreatitis were abdominal pain (4 patients) with or without nausea/vomiting (2 patients). The median serum lipase elevation was 10 times the upper limit of normal (range, 3.53-10 IU/L). A large increase in gamma-glutamyl transferase (GGT) levels was observed in 6 of the 11 patients (median elevation from 4.95 [2-7.4] to 14.35 [6-30] the upper limit of normal). By contrast, alanine aminotransferase (ALT) and alkaline phosphatase (alk Ph) levels were not significantly different from baseline values.
All but 1 of the patients (the patient with neuropathy) made a full recovery. However, one patient (patient 6) died 15 months later from liver failure, despite a sustained HCV virologic response.
Factors Associated With Symptomatic Mitochondrial Toxicity
Univariate analysis showed no association with age, gender, the body mass index, HCV transmission group, AIDS status, CD4 cell count, HIV viral load, mean duration of antiretroviral treatment, mean duration of HIV or HCV infection, ALT, GGT, or alk Ph levels, HCV viral load and HCV genotype, mean Metavir inflammation and fibrosis scores, or the HCV treatment arm (pegIFN plus ribavirin or standard IFN plus ribavirin) (Table 3).
The possible role of antiretroviral agents was analyzed by both single NRTI, NNRTI, and PI used at the initiation of anti-HCV treatment. Univariate analysis showed no association with PI- or NNRTI-containing regimens. Among the NRTIs, only ddI was significantly associated with an increased risk of symptomatic mitochondrial toxicity. To study the impact of specific NRTI combinations, 4 groups of NRTI regimens were determined a priori. Two contained ddI (with or without d4T), 1 contained d4T but not ddI, and 1 contained neither ddI nor d4T. Eighty-three patients received regimens that included ddI, either with d4T (n = 52) or without d4T (n = 31). Symptomatic mitochondrial toxicity occurred in 8 (15.4%) of the 52 patients treated with ddI and d4T and in 3 (9.6%) of the 31 patients treated with ddI without d4T. No cases occurred among the 122 patients receiving d4T without ddI or in the 112 patients receiving an NRTI regimen containing neither d4T nor ddI. Multivariate analysis showed that ddI, with or without d4T, was associated with symptomatic mitochondrial toxicity (OR 46, 95% CI, 7.4 to infinity; P < 0.001) compared with regimens with neither ddI nor d4T. The risk of symptomatic mitochondrial toxicity was not increased in patients treated with d4T without ddI (OR 1.8; 95% CI, 0.4-11.3). Likewise, triple-NRTI regimens without ddI were not associated with symptomatic mitochondrial toxicity. The risk of symptomatic mitochondrial toxicity associated with ddI was similar whether patients were receiving 1 or 2 other NRTIs.
The incidence of symptomatic hyperlactatemia in adults receiving at least 1 NRTI has been estimated in 2 prospective studies to be 8 to 20.9 per 1000 patient-years.8,9 In our study, as in HCV-monoinfected patients treated with the IFN-ribavirin combination, we observed no cases of symptomatic mitochondrial toxicity in patients receiving anti-HCV treatment without concurrent antiretroviral therapy. Conversely, the incidence of symptomatic mitochondrial toxicity in patients receiving both anti-HCV and anti-HIV therapy was higher (47.5 per 1000 patient-years, based on 278 patient-years of ribavirin therapy) than that reported in patients receiving anti-HIV treatment alone, suggesting that an interaction between the 2 treatments increases the risk of symptomatic mitochondrial toxicity.
We found that concomitant ddI therapy in patients receiving both IFN (standard or pegylated) and ribavirin was associated with an adjusted 46-fold increase in the risk of symptomatic mitochondrial toxicity compared with patients receiving antiretroviral regimens that did not contain ddI. The incidence of symptomatic mitochondrial toxicity was 200.2 per 1000 patient-years (based on 55 patient-years of ddI and ribavirin therapy), pointing to synergism between ddI with ribavirin. Indeed, although the lack of a no-ribavirin arm theoretically undermines the conclusion that these events are related to ribavirin rather than interferon, in vitro studies had shown that ribavirin enhances both the efficacy and the toxicity of ddI.10-13 Furthermore, all previously reported HIV/HCV-coinfected patients who developed symptomatic mitochondrial toxicity while receiving IFN (standard or pegylated) combined with ribavirin, in addition to anti-HIV therapy, were also receiving ddI.5,6,14-16
In our study the incidence of symptomatic mitochondrial toxicity was not significantly different between patients who were taking both ddI and d4T and those taking ddI alone or combined with NRTIs other than d4T. No cases were observed among patients treated with d4T without ddI, or with a triple-NRTI combination without ddI. This is consistent with the results of an in vitro study showing that mitochondrial DNA depletion in hepatocytic cells due to the ddI-d4T combination was not more severe than with ddI alone.17 Our results are also in keeping with those of a large cross-sectional study, in which ddI-containing regimens doubled the relative risk of hyperlactatemia, whereas the risk was similar with d4T and zidovudine; the incidence in the 2 groups depended on whether the latter drugs were combined with ddI or 3TC.18
Mitochondrial toxicity can produce a broad spectrum of clinical disorders, but initial symptoms (nausea, vomiting, and abdominal pain or, in cases with more insidious onset, fatigue and weight loss) are generally nonspecific.8,19 In our patients, the clinical manifestations usually consisted of weight loss, weakness, nausea, and abdominal pain and were therefore indistinguishable from common adverse effects of IFN-ribavirin combination therapy.1,2 Serum lactate and lipase should therefore be assayed in patients presenting with these manifestations or with more acute symptoms. Attention must also be paid to gradually increasing GGT levels, as this is not a common effect of HCV infection. As in previously reported cases of symptomatic mitochondrial dysfunction, we noted a gradual significant increase in GGT levels (mean 14.35, range 6-30 upper limit of normal (ULN) in 6 of our patients.5,15 The pancreatic toxicity of ddI is dose related: its frequency is 1% to 7% with currently recommended doses, and most cases occur within the first 6 months of therapy.20-22 In our study the observed incidence of pancreatitis in ddI-treated patients was 6%; it might have been higher, however, as amylase and lipase were not routinely assayed during the trial. The median duration of ddI therapy at the diagnosis of pancreatitis was 14 months (range, 3-24 months), suggesting that the addition of ribavirin increased the risk (median duration of HCV treatment: 26 weeks; range, 15-48 weeks).
In this study, no cases of symptomatic mitochondrial toxicity occurred in anti-HCV-treated patients who were not also taking antiretroviral therapy or whose antiretroviral regimen did not contain ddI. Conversely, concomitant treatment with ddI and the IFN-ribavirin combination resulted in a 46-fold increase in the relative risk of symptomatic mitochondrial toxicity. These results, together with other published data, suggest that coadministration of ribavirin and ddI should be avoided; if unavoidable, patients should be monitored closely for signs of mitochondrial toxicity.
The authors thank David Young for editing the manuscript.
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Keywords:© 2005 Lippincott Williams & Wilkins, Inc.
HIV/hepatitis C virus coinfection; hyperlactatemia; lactic acidosis; pancreatitis; didanosine and ribavirin