Limited sampling strategies for the estimation of atazanavir daily exposure in HIV-infected patients

Concomitant Use of Cotrimoxazole and Atazanavir in HIV-infected Patients: A Therapeutic Drug Monitoring and Pharmacovigilance Based Dual Approach

BACKGROUND

Cotrimoxazole is the main antibiotic used in primary prophylaxis for opportunistic infections in advanced HIV infection. This drug can inhibit one of the metabolic pathways of atazanavir (ATV), such as the cytochromes P450 (CYP) 2C8/2C9 and could interfere with its safety and efficacy.

OBJECTIVE

We studied the drug-drug interaction (DDI) between cotrimoxazole and ATV by using therapeutic drug monitoring (TDM) and pharmacovigilance (PV) approaches.

METHODS

We compared a group of patients treated with cotrimoxazole and receiving an ATV-based regimen to controls. This historical cohort analysis used data from Dat'AIDS in HIV-infected patients who had at least two lowest plasma concentrations (C-trough) of ATV during their outpatient follow-up. Likewise, we used the international pharmacovigilance data from VigiBase to evaluate the notifications of hyperbilirubinemia reported with ATV.

RESULTS

In the TDM analysis, the two groups of patients (treated with cotrimoxazole and controls) were almost homogeneous concerning the main baseline features. After at least six months of ATVbased regimen, there was no significant difference in the safety threshold of the ATV C-trough [with an adjusted odds ratio (aOR) of 1.4 (95% CI: 0.5 - 4.4)] compared to controls. We observed similar results with the efficacy thresholds of ATV C-trough. Regarding the PV analysis, there was no difference in hyperbilirubinemia occurring with ATV when cotrimoxazole was concomitant, with an adjusted reporting odds ratio (aROR) of 0.9 (95% CI: 0.6 to 1.2).

CONCLUSION

This study showed a relevant concomitant use between Cotrimoxazole and ATV based on TDM and PV approaches.

Retrospective analysis of the associations and effectiveness of performing therapeutic drug monitoring in pregnant HIV-positive women in two large centres in Manchester

There is no proven benefit for the routine use of therapeutic drug monitoring in HIV-positive pregnant women either for improving viral control or preventing mother-to-child transmission. This analysis reviewed a cohort of 171 HIV-positive pregnant women delivering between 1 January 2008 and 28 May 2013 to first establish which baseline characteristics are associated with having therapeutic drug monitoring performed, and whether therapeutic drug monitoring was associated with improved HIV control during pregnancy or mother-to-child transmission. Therapeutic drug monitoring was performed in 39% ( n = 66) of patients; it was associated with baseline characteristics of poor adherence to therapy (therapeutic drug monitoring 23% versus non-therapeutic drug monitoring 10%, p = 0.025) and the use of protease inhibitors (therapeutic drug monitoring 94% versus non-therapeutic drug monitoring 77%, p = 0.005). By multivariate analysis therapeutic drug monitoring was associated with medication alterations during pregnancy (therapeutic drug monitoring 68% versus non-therapeutic drug monitoring 12%, p = < 0.001), but not associated with any difference in viral load breakthrough during pregnancy (therapeutic drug monitoring 12% versus non-therapeutic drug monitoring 7%, p = 0.456) and viral load detectable at birth (therapeutic drug monitoring 14% versus non-therapeutic drug monitoring 9%, p = 0.503). There were no instances of mother-to-child transmission. Therapeutic drug monitoring's association with medication changes is postulated as partially causal in this cohort. There was no evidence of any association with improved control or reduced transmission of HIV to advocate routine therapeutic drug monitoring use.

The use of TDM in pregnant HIV-positive women: a retrospective cross-sectional review of five years practice in two large hospitals in Manchester

Introduction

Despite plasma levels of certain HIV drugs decreasing in the third trimester of pregnancy there is no definitive evidence that therapeutic drug monitoring (TDM) improves HIV control and prevents mother-to-child transmission (MTCT). Indeed “one-off” TDM measurements are thought to poorly correlate with overall drug exposure [1]. We aim to describe baseline demographic and clinical characteristics of pregnant women with HIV, and to compare their HIV control, management during pregnancy and neonatal outcomes with respect to whether TDM was performed.

Materials and Methods

Retrospective cross-sectional case note analysis was performed on pregnant women with HIV who attended North Manchester General Hospital and Manchester Royal Infirmary from 1st January 2008 to 28th May 2013.

Results

A total of 171 pregnancies were included; 39% (n=66) had TDM. The majority of patients were of African origin (85%) and age range was 16–42 years (median 32 years). TDM was found to be associated with a history of poor adherence to therapy (TDM 23%, vs no TDM 10%, p=0.017), although baseline viral load (VL) and CD4 counts were comparable between TDM and non-TDM groups (p=0.4756 and 0.9492, respectively). TDM was also associated with protease inhibitors (PI) (TDM 94% vs no TDM 77%, p= 0.004). Within the PI group, TDM was more strongly associated with atazanavir use than other PI's (55%, p=0.023). TDM was not associated with any other demographic variable or with either of the two hospital sites (p=0.427). TDM was associated with medication alterations during pregnancy (TDM 67% vs no TDM 13%, p=0.052), but was not associated with any difference in outcomes with similar proportions of newly detectable VL during pregnancy (TDM 12% vs no TDM 7%, p=0.220) and VL detectable at birth (TDM 14% vs no TDM 9%, p= 0.293). There were no instances of MTCT.

Conclusions

TDM was associated with PI use and a history of poor adherence at baseline. TDM was not associated with improved HIV control during pregnancy and there was no MTCT. TDM was not shown to have any additional benefit in pregnancy and its routine use is not recommended to improve HIV control or reduce MTCT.