Adjusting Antiretroviral Therapy Dosage Using Therapeutic Drug Monitoring
Status:
Unknown status
Trial end date:
2009-04-01
Target enrollment:
Participant gender:
Summary
Background
Low concentrations of protease inhibitors (PIs) or nonnucleoside reverse transcriptase
inhibitors (NNRTIs) are associated with an increased risk of virological failure. Likewise,
excessive antiretroviral drug concentrations increase the risk of toxicity. Therapeutic drug
monitoring (TDM) may identify and correct excessively high or low PI and/or NNRTI
concentrations, and thus minimize toxicity and risk of treatment failure. Treatment
guidelines only recommend using TDM to help optimize ARV therapy in selected patients, and
there are no clear recommendations to guide the clinician who decides to adjust drug doses.
Prospective studies have demonstrated the relationship between EFV plasma concentration and
neuropsychiatric symptoms. Moreover, EFV is metabolized mainly by cytochrome P450 2B6 and its
concentration was reported to be associated with the CYP2B6 516GrT genetic polymorphism.
For drugs such as EFV or LPV/r, lower doses than the ones validated for standard clinical use
have demonstrated efficacy in dose-ranging studies.
The investigators will use a standardised algorithm to reduce doses in patients with plasma
EFV or LPV/r concentration above percentile 75. This algorithm is based on a Bayesian
approach from the pharmacology unit in Lausanne. The investigators hypothesize that a dosage
individualisation is feasible and safe.
2.2 Study Aims
The investigators aim at testing a simplified algorithm for dose reduction in patients with
documented virological efficacy, treated by a stable LPV/r or EFV based regimen with elevated
plasma concentration of these drugs.
Study Design
Prospective open label study in which all eligible patients screened with a plasma drug
concentration of either EFV or LPV/r above percentile 75 will be included. After confirmation
of the results at baseline, patients will be offered to decrease drug dosage by a third or a
half according to a standardised algorithm. All patients will undergo HIVRNA, biochemistry
and validated questionnaires after 3 and 6 months to assess the safety and the benefit of
this strategy.