Population pharmacokinetic/pharmacogenetic model for optimization of efavirenz therapy in Caucasian HIV-infected patients.

Despite extensive clinical experience with efavirenz (EFV), unpredictable interindividual variabilities in efficacy and toxicity remain important limitations associated with the use of this antiretroviral. The purpose of this study was to determine the factors affecting EFV pharmacokinetics and to develop a pharmacokinetic/pharmacogenetic (PK/PG) model in a Caucasian population of HIV-infected patients. In total, 869 EFV plasma concentrations from 128 HIV-infected patients treated with EFV were quantitatively assessed using a validated high-performance liquid chromatography technique. All patients were genotyped for 90 single nucleotide polymorphisms (SNPs) in genes coding for proteins involved in the metabolism and transport of EFV, using a MassArray platform provided by Sequenom. The influence of these polymorphisms on EFV pharmacokinetics and the effects of demographic, clinical, biochemical, lifestyle, and concurrent drug covariates were evaluated. Plasma concentrations were fitted by a one-compartment model, with first-order absorption and elimination using nonlinear mixed-effect modeling (NONMEM program). The CYP2B6*6 allele, multidrug resistance-associated protein 4 (MRP4) 1497C → T, and gamma-glutamyltranspeptidase (GGT) were identified as major factors influencing the apparent EFV oral clearance (CL/F), reducing the initial interindividual variability by 54.8%, according to the model CL/F = (12.2 - 0.00279 · GGT) · 0.602(CYP2B6*6 [G/T]) · 0.354(CYP2B6*6 [T/T]) · 0.793(MRP4 1497C → T), where CYP2B6*6 [G/T], CYP2B6*6 [T/T], and MRP4 1497C → T take values of 0 or 1 to indicate the absence or presence of polymorphisms. The detailed genetic analysis conducted in this study identified two of 90 SNPs that significantly impacted CL/F, which might indicate that the remaining SNPs analyzed do not influence this PK parameter, at least in Caucasian populations with characteristics similar to those of our study population.

Factors influencing adherence to highly active antiretroviral therapy in Spain.

BACKGROUND: Multiple factors have been previously described which could influence adherence to HAART. Our objective is to determine the fundamental factors which influence adherence to highly active antiretroviral therapy in our population. METHODS: A cross-sectional study was made selecting 143 outpatients attending our hospital HIV unit. 22 factors were recorded which could influence adherence to treatment (covering individual factors, the illness itself, the therapeutic regimen and the medical team). Adherence was estimated by the combination of two methods (self-report and pharmacy data); statistical analysis was performed using univariate and multivariate methods. RESULTS: 96 patients (67.13%) had good adherence and 47 (32.87%) did not. Only 3 of the 22 factors studied were significant and independent factors related with adherence: employment, housing situation and degree of treatment acceptance. CONCLUSIONS: we have found some differences regarding HAART adherence in our population compared with previous studies. Psychosocial and behavioral factors were the principal ones. We must try to detect patients at high risk of non-adherence in order to take therapeutic decisions properly, try to reinforce adherence and modify the factors associated with poor adherence.

Hyperhidrosis in association with efavirenz.

Hyperhidrosis may be an adverse drug event (ADE) induced by the effect on any of the components of human thermoregulation. Some of our efavirenz (EFV)-treated patients have reported excessive nocturnal sweating that resolved after dose reduction. A representative clinical case of a male patient being treated with a night-time 600-mg dose of EFV who reported severe nocturnal sweating is reported here. His EFV plasma concentrations were always above normal and he was homozygous for a deficient function-allele of CYP2D6; for this reason, his EFV dose was reduced to 400mg=d. Simultaneous with this reduction, the patient described a progressive decrease in nocturnal sweating until its complete disappearance 15-20 days after this new drug dosage. The mechanism explaining sweating could be similar to the one suggested for hyperhidrosis related to serotonin uptake inhibitors, because this hyperhidrosis is episodic, nocturnal, and dose dependent. Hyperhidrosis could correspond to a dose-dependent ADE induced by EFV, therefore, a reduction of EFV from 600 to 400mg/d seems to control it. EFV crosses the hematoencephalic barrier and reaches a mean concentration in the cerebroespinal fluid equivalent to 0.69% of the plasma concentration. The ability of EFV to accessing the central nervous system (CNS) could explain an effect on thermoregulation. Hyperhydrosis is not easily discovered through a routine anamnesis because it is not noted on the EFV package insert, so its incidence may be higher than expected. Additionally, hyperhidrosis may be an indicator of elevated EFV plasma concentrations and hence may be controlled through a reduction of dose.

Adherence to highly active antiretroviral therapy in HIV-infected inmates.

Adherence to highly active antiretroviral therapy (HAART) has been scarcely studied in correctional settings. Our study aims to evaluate the relationship between adherence and virological outcome and to determine factors related to adherence in correctional settings. A cross-sectional retrospective study was performed in Topas prison (Salamanca, Spain). 50 inmates starting HAART were studied. Adherence was estimated through a self-report questionnaire and variables related to adherence (covering individual factors, the illness itself and the therapeutic regimen) were recorded. HIV-RNA levels and CD4 lymphocyte count were measured before starting therapy and six months after. Statistical analysis was performed using univariate and multivariate methods. 21 inmates (42%) were considered adherent and 29 (58%) were non-adherent. Adherence to treatment, as measured by our questionnaire, was the only significant and independent factor associated with an undetectable viral load at six months of therapy. Five variables were significantly associated with adherence to treatment, four of them as predictor factors for good adherence: an active occupation inside prison, the absence of HIV-related symptoms, a good or average acceptance of treatment, and a higher academic background; previous injection drug use as a risk factor for HIV transmission was associated with non-adherence. A simple self-report questionnaire may be useful for assessing adherence in prison inmates. Recognizing variables associated with adherence is essential to identify prisoners at high risk of being non-adherents in order to develop strategies for improving compliance.