Drug-drug Interactions Between Antiretroviral Drugs and Cardiovascular Drugs in Elderly Patients From the Swiss HIV Cohort Study

HIV-infected individuals live longer, making the proportion of older individuals within the HIV infected population constantly growing. Thus, the management of HIV infection is becoming more complex as patients encounter more age related chronic ailments such as hypertension, diabètes and tumors, or acute diseases, sometimes severe, leading to polypharmacy and consequently to potential drug-drug interactions (DDI). In addition, aging is characterized by a decline in the function of elimination organs, which may impact the pharmacokinetics of drugs and thereby the magnitude of DDI.

The principal aim of the study is to determine the importance of DDIs between antiretroviral drugs and commonly prescribed co-medications (namely amlodipine, rosuvastatin and atorvastatin) in HIV-infected patients of the Swiss HIV Cohort Study (SHCS). The investigation will include a majority of patients over 60 years old, yet without excluding younger patients. Pharmacokinetic investigations will be primarily conducted in patients treated with darunavir/ritonavir- or dolutegravir-containing regimens, and who receive one of the cardiovascular drug of interest. The objective is to contrast the effects of darunavir/ritonavir (strong inhibitor of drug metabolizing cytochromes) and dolutegravir (devoid of inhibitory effects on these enzymes), in order to determine the magnitude of the interaction with the co-medication. Besides their common use in elderly HIV-infected patients, amlodipine, atorvastatin and rosuvastatin were primarily selected due to their predisposition to become victims of drug-drug interactions. In addition, the same study framework will possibly serve to examine further drug combinations susceptible to interact, whose exploration could be of interest from a clinical point a view to stimulate future confirmatory research. It will thus be open to investigate associations of other cardiovascular agents with the antiretroviral drugs defined above, or with other antiretroviral drugs.

On a morning selected for investigation, the patient will take the antiretroviral medications together with the comedication of interest with a standard breakfast. Serial blood samples will be collected into EDTA-K monovettes (2.7 ml) from a catheter positioned in the forearm at the following time-points: t = 0 (just before the drug intake) and 30 minutes, 1, 2, 3, 4, 6, 8, 10, and 12 hours after drug intake (a certain flexibility in sampling times is allowed, provided that dosing and sampling times are carefully recorded). The patient will then spend the night at home and return the following morning to provide the last sample of blood 24 hours after drugs intake. In total, 30 ml of blood will be required for a full pharmacokinetic investigation).

A second full pharmacokinetic investigation will be performed for patients undergoing antiretroviral treatment change for clinical reasons. The investigation will be scheduled two weeks after switching treatment, so that a steady-state is reached, and will be performed as described above.

The blood samples will be centrifuged and the separated plasma will be frozen at -80°C until analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters will be first estimated by classical non-compartmental approaches: Maximal concentration (Cmax), minimal concentration (Cmin), Area Under the Curve (AUC), slope of the terminal phase (Lambda_z), clearance (Cl), half-life (t1/2). These parameters will be compared according to the co-prescription of darunavir/ritonavir versus dolutegravir, using a variance analysis on log-transformed values. The analysis will accommodate partial pairing of parameter values obtained in patients investigated in cross-over, through the inclusion of a random patient factor (assumed to take independent values only between patients). PK parameters of antiretroviral drugs will be simply described.