Correlations between imatinib pharmacokinetics, pharmacodynamics, adherence, and clinical response in advanced metastatic gastrointestinal stromal tumor (GIST): An emerging role for drug blood level testing?

Imatinib is the standard of care for patients with advanced metastatic gastrointestinal stromal tumors (GIST), and is also approved for adjuvant treatment in patients at substantial risk of relapse. Studies have shown that maximizing benefit from imatinib depends on long-term administration at recommended doses. Pharmacokinetic (PK) and pharmacodynamic factors, adherence, and drug-drug interactions can affect exposure to imatinib and impact clinical outcomes. This article reviews the relevance of these factors to imatinib's clinical activity and response in the context of what has been demonstrated in chronic myelogenous leukemia (CML), and in light of new data correlating imatinib exposure to response in patients with GIST. Because of the wide inter-patient variability in drug exposure with imatinib in both CML and GIST, blood level testing (BLT) may play a role in investigating instances of suboptimal response, unusually severe toxicities, drug-drug interactions, and suspected non-adherence. Published clinical data in CML and in GIST were considered, including data from a PK substudy of the B2222 trial correlating imatinib blood levels with clinical responses in patients with GIST. Imatinib trough plasma levels <1100ng/mL were associated with lower rates of objective response and faster development of progressive disease in patients with GIST. These findings have been supported by other analyses correlating free imatinib (unbound) levels with response. These results suggest a future application for imatinib BLT in predicting and optimizing therapeutic response. Nevertheless, early estimates of threshold imatinib blood levels must be confirmed prospectively in future studies and elaborated for different patient subgroups.

Residual antimalarials in malaria patients from Tanzania--implications on drug efficacy assessment and spread of parasite resistance.

Repeated antimalarial treatment for febrile episodes and self-treatment are common in malaria-endemic areas. The intake of antimalarials prior to participating in an in vivo study may alter treatment outcome and affect the interpretation of both efficacy and safety outcomes. We report the findings from baseline plasma sampling of malaria patients prior to inclusion into an in vivo study in Tanzania and discuss the implications of residual concentrations of antimalarials in this setting. In an in vivo study conducted in a rural area of Tanzania in 2008, baseline plasma samples from patients reporting no antimalarial intake within the last 28 days were screened for the presence of 14 antimalarials (parent drugs or metabolites) using liquid chromatography-tandem mass spectrometry. Among the 148 patients enrolled, 110 (74.3%) had at least one antimalarial in their plasma: 80 (54.1%) had lumefantrine above the lower limit of calibration (LLC = 4 ng/mL), 7 (4.7%) desbutyl-lumefantrine (4 ng/mL), 77 (52.0%) sulfadoxine (0.5 ng/mL), 15 (10.1%) pyrimethamine (0.5 ng/mL), 16 (10.8%) quinine (2.5 ng/mL) and none chloroquine (2.5 ng/mL). The proportion of patients with detectable antimalarial drug levels prior to enrollment into the study is worrying. Indeed artemether-lumefantrine was supposed to be available only at government health facilities. Although sulfadoxine-pyrimethamine is only recommended for intermittent preventive treatment in pregnancy (IPTp), it was still widely used in public and private health facilities and sold in drug shops. Self-reporting of previous drug intake is unreliable and thus screening for the presence of antimalarial drug levels should be considered in future in vivo studies to allow for accurate assessment of treatment outcome. Furthermore, persisting sub-therapeutic drug levels of antimalarials in a population could promote the spread of drug resistance. The knowledge on drug pressure in a given population is important to monitor standard treatment policy implementation.

Influence of noninjecting and injecting drug use on mortality, retention in the cohort, and antiretroviral therapy, in participants in the Swiss HIV Cohort Study.

OBJECTIVES: We studied the influence of noninjecting and injecting drug use on mortality, dropout rate, and the course of antiretroviral therapy (ART), in the Swiss HIV Cohort Study (SHCS). METHODS: Cohort participants, registered prior to April 2007 and with at least one drug use questionnaire completed until May 2013, were categorized according to their self-reported drug use behaviour. The probabilities of death and dropout were separately analysed using multivariable competing risks proportional hazards regression models with mutual correction for the other endpoint. Furthermore, we describe the influence of drug use on the course of ART. RESULTS: A total of 6529 participants (including 31% women) were followed during 31 215 person-years; 5.1% participants died; 10.5% were lost to follow-up. Among persons with homosexual or heterosexual HIV transmission, noninjecting drug use was associated with higher all-cause mortality [subhazard rate (SHR) 1.73; 95% confidence interval (CI) 1.07-2.83], compared with no drug use. Also, mortality was increased among former injecting drug users (IDUs) who reported noninjecting drug use (SHR 2.34; 95% CI 1.49-3.69). Noninjecting drug use was associated with higher dropout rates. The mean proportion of time with suppressed viral replication was 82.2% in all participants, irrespective of ART status, and 91.2% in those on ART. Drug use lowered adherence, and increased rates of ART change and ART interruptions. Virological failure on ART was more frequent in participants who reported concomitant drug injections while on opiate substitution, and in current IDUs, but not among noninjecting drug users. CONCLUSIONS: Noninjecting drug use and injecting drug use are modifiable risks for death, and they lower retention in a cohort and complicate ART.

Current trends in illegal drug use and drug related health problems in Switzerland.

As part of the evaluation of the Confederation's measures to reduce drug related problems, a review of available data on drug use and drug related problems in Switzerland has been conducted. Source of data included: population surveys (adults and teenagers), surveys among drug users, health statistics (drug related and AIDS related deaths, HIV case reporting, drug treatments) police statistics (denunciations for consumption). The aims of reducing the number of dependent hard drug users have been achieved where heroin is concerned. In particular, there seems to have been a decrease in the number of people becoming addicted to this substance. For all other illegal substances, especially cannabis, the trend is towards an increased use, as in many European countries. As regards dependent drug users, especially injecting drug users, progress has been made in the area of harm reduction and treatment coverage. This epidemiological assessment can be used in the discussions currently engaged about the revision of the Law governing narcotics and will be a baseline for future follow up of the situation.

Stage of change of cigarette smoking in drug dependent patients.

Nicotine cessation programmes in Switzerland, which are commonly based on the stage of change model of Prochaska and DiClemente (1983), are rarely offered to patients with illicit drug dependence. This stands in contrast to the high smoking rates and the heavy burden of tobacco-related problems in these patients. The stage of change was therefore assessed by self-administered questionnaire in 100 inpatients attending an illegal drug withdrawal programme. Only 15% of the patients were in the contemplation or decision stage. 93% considered smoking cessation to be difficult or very difficult. These data show a discrepancy between the motivation to change illegal drug consumption habits and the motivation for smoking cessation. The high proportion of patients remaining in the precontemplation stage for smoking cessation, in spite of their motivation for illicit drug detoxification, may be due to the perception that cessation of smoking is more difficult than illicit drug abuse cessation.

HIV-1 superinfection with a triple-class drug-resistant strain in a patient successfully controlled with antiretroviral treatment.

We report a case of HIV-1 superinfection (HSI) with a clade B, triple-class resistant virus in a patient successfully controlling viremia with continuous combination antiretroviral therapy started 8 years earlier during primary HIV infection. The course of HIV infection prior to HSI was monitored in both the source partner and recipient (8 and 11 years, respectively) and 4 years following HSI. This case report demonstrates re-infection with HIV-1 despite effective combination antiretroviral therapy.

Unlicensed and off-label drug use in a Swiss paediatric university hospital.

BACKGROUND: Many medicines used in newborns, infants, children and adolescents are not licensed ("unlicensed") or are prescribed outside the terms of the marketing authorization ("off-label"). Several studies have shown that this is a common practice in various healthcare settings in the USA, Europe and Australia, but data are scarce in Switzerland. OBJECTIVES: The aim of our prospective study was to determine the proportion of unlicensed or off-label prescriptions in paediatric patients. METHODS: This pilot study was conducted prospectively over a six month period in the department of paediatrics of a university hospital. RESULTS: Sixty patients aged from three days to 14 years were included in the study. A total of 483 prescriptions were written for the patients. More than half of all prescriptions (247; 51%) followed the terms of the marketing authorization. 114 (24%) were unlicensed and 122 (25%) off-label. All patients received at least one unlicensed or offlabel medicine. CONCLUSION: The use of unlicensed or off-label medicines to treat children was found to be common. Co-operation between the pharmaceutical industry, national regulatory authorities, clinical researchers, healthcare professionals and parents is required in order to ensure that children do not remain "therapeutic orphans".

Pediatric drug-related problems: a multicenter study in four French-speaking countries.

BACKGROUND: Pediatric intensive care patients represent a population at high risk for drug-related problems. There are few studies that compare the activity of clinical pharmacists between countries. OBJECTIVE: To describe the drug-related problems identified and interventions by four pharmacists in a pediatric cardiac and intensive care unit. SETTING: Four pediatric centers in France, Quebec, Switzerland and Belgium. METHOD: This was a six-month multicenter, descriptive and prospective study conducted from August 1, 2009 to January 31, 2010. Drug-related problems and clinical interventions were compiled from four pediatric centers in France, Quebec, Switzerland and Belgium. Data on patients, drugs, intervention, documentation, approval and estimated impact were compiled. MAIN OUTCOME MEASURE: Number and type of drug-related problems encountered in a large pediatric inpatient population. RESULTS: A total of 996 interventions were recorded: 238 (24 %) in France, 278 (28 %) in Quebec, 351 (35 %) in Switzerland and 129 (13 %) in Belgium. These interventions targeted 270 patients (median 21 months old, 53 % male): 88 (33 %) in France, 56 (21 %) in Quebec, 57 (21 %) in Switzerland and 69 (26 %) in Belgium. The main drug-related problems were inappropriate administration technique (29 %), untreated indication (25 %) and supra-therapeutic dose (11 %). The pharmacists' interventions were mostly optimizing the mode of administration (22 %), dose adjustment (20 %) and therapeutic monitoring (16 %). The two major drug classes that led to interventions were anti-infectives for systemic use (23 %) and digestive system and metabolism drugs (22 %). Interventions mainly involved residents and all clinical staff (21 %). Among the 878 (88 %) proposed interventions requiring physician approval, 860 (98 %) were accepted. CONCLUSION: This descriptive study illustrates drug-related problems and the ability of clinical pharmacists to identify and resolve them in pediatric intensive care units in four French-speaking countries.

Surveillance of HIV type 1 drug resistance among naive patients from Venezuela.

We have studied 65 HIV-1-infected untreated patients recruited in Caracas, Venezuela with TCD4 counts > or =350/microl. The reverse transcriptase and protease sequences of the virus were sequenced, aligned with reference HIV-1 group M strains, and analyzed for drug resistance mutations. Most of the viruses were subtype B genotype in both the protease and RT genomic regions. Five of the 62 virus isolates successfully amplified showed evidence of recombination between protease and RT, with their protease region being non-B while their RT region was derived from subtype B. Four strains were found bearing resistance mutations either to NRTIs, NNRTIs, or PIs. The prevalence of HIV-1 isolates bearing resistance mutations was therefore above the 5% threshold of WHO.