Does Once-Daily Raltegravir Have Any Role in the Antiretroviral Treatment?

Administering raltegravir once daily would make adherence to antiretroviral treatment easier, especially if the concomitant drugs are also administered once daily. We report our experience on the use of raltegravir, both once- and twice-daily.Retrospective review of HIV-infected patients on treatment with raltegravir 800 mg once or 400 mg twice a day plus 2 analogs. Patients were classified as group A (subjects switched to raltegravir due to adverse events on a previous regimen or drug-drug interactions) and group B (subjects who restarted antiretroviral treatment after a previous drop-out). The primary clinical endpoint was the percentage of subjects with virological suppression after 96 weeks. Treatment's effectiveness (noncomplete/missing equals failure) was also evaluated. Pharmacokinetic study was performed in unselected patients. Plasma raltegravir concentrations were determined by high-performance liquid chromatography coupled with mass spectrometry.A total of 133 patients were included in the study (74 and 59 on raltegravir once- and twice-daily). There were only 4 virological failures in the entire cohort during the follow-up. Thus, the Kaplan-Meier estimation of efficacy by on-treatment analysis was 96.3% (CI95, 92.8-99.8) at week 96, independently of the dosing regimen and of the raltegravir concentrations. Similar exposures to raltegravir based on AUC0-τ, but higher Cmax and significantly lower Ctrough were observed when raltegravir was given once daily compared with 400 mg twice daily. In fact, 14 out of 56 Ctrough concentrations (25%) from patients taking raltegravir once daily were below the IC95 of wild-type HIV-1 clinical isolates while only 2 samples from patients receiving 400 mg twice a day were below this value, although no relationship between Ctrough and efficacy was found. The main limitations of the study are that the raltegravir dosing regimen was not randomized and more than 50% of the patients were virologically suppressed at baseline.Regimens comprising raltegravir 800 mg once daily plus 2 nucleos(t)ide reverse transcriptase inhibitors can be an efficacious and safe option, particularly in virologically suppressed patients and those with a viral load <100,000 copies/mL.

Telaprevir and ribavirin interaction: higher ribavirin levels are not only due to renal dysfunction during triple therapy.

A higher incidence of anemia has been observed during the treatment of hepatitis C virus genotype 1 (HCV-1) infection with pegylated alpha interferon (pegIFN-α), ribavirin, and telaprevir. We assessed the impacts that concomitant administration of telaprevir and changes in the glomerular filtration rate have on ribavirin plasma levels. The minimum concentrations of ribavirin in plasma (ribavirin Cmin) determined during triple therapy including telaprevir were compared with those observed after telaprevir withdrawal and those observed in the same subjects and in a large cohort during a previous course of pegIFN-α plus ribavirin. Intensive pharmacokinetic sampling for ribavirin was performed at steady state during the triple-therapy phase. Ribavirin levels were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Twenty-seven HCV-1/HIV-coinfected patients were enrolled. The median ribavirin Cmin for triple therapy (4.08 µg/ml; range, 2.14 to 5.56 µg/ml) was higher than that observed after telaprevir withdrawal (1.96 µg/ml; range, 0.41 to 3.45 µg/ml) (P < 0.001) and that observed for 125 HCV-1/HIV-coinfected patients treated only with pegIFN-α plus ribavirin (1.65 µg/ml; range, 0.41 to 5.56 µg/ml) (P < 0.001). The estimated glomerular filtration rate (eGFR) decreased >20% from the baseline value in 11 of 27 patients and became normal after telaprevir removal in almost all cases. There was a negative correlation between eGFR and ribavirin clearance (r(2) = 0.257; P = 0.064) but not the ribavirin area under the concentration-time curve from 0 to 12 h (AUC0-12) (r(2) = 0.001; P = 0.455). Thus, there is a significant pharmacokinetic interaction between telaprevir and ribavirin that results in very high ribavirin levels, which explains the excess of toxicity observed with this drug combination. A blockade of the proximal tubular transporters might be implicated in both the increase in plasma creatinine and the high ribavirin levels. (This study has been registered at ClinicalTrials.gov under registration no. NCT01818856.).