Therapeutic Drug Monitoring (TDM) of Imatinib: Effectiveness of Bayesian dose adjustment for CML patients enrolled in the Imatinib Concentration Monitoring (I-COME) study

Introduction: As imatinib pharmacokinetics are highly variable, plasma levels differ largely between patients under the same dosage. Retrospective studies in chronic myeloid leukemia (CML) patients showed significant correlations between low levels and suboptimal response, as well as between high levels and poor tolerability. Monitoring of trough plasma levels, targeting 1000 μg/L and above, is thus increasingly advised. Our study was launched to assess prospectively the clinical usefulness of systematic imatinib TDM in CML patients. This preliminary analysis addresses the appropriateness of the dosage adjustment approach applied in this study, which targets the recommended trough level and allows an interval of 4-24 h after last drug intake for blood sampling. Methods: Blood samples from the first 15 patients undergoing 1st TDM were obtained 1.5-25 h after last dose. Imatinib plasma levels were measured by LC-MS/MS and the concentrations were extrapolated to trough based on a Bayesian approach using a population pharmacokinetic model. Trough levels were predicted to differ significantly from the target in 12 patients (10 <750 μg/L; 2 >1500 μg/L along with poor tolerance) and individual dose adjustments were proposed. 8 patients underwent a 2nd TDM cycle. Trough levels of 1st and 2nd TDM were compared, the sample drawn 1.5 h after last dose (during distribution phase) was excluded from the analysis. Results: Individual dose adjustments were applied in 6 patients. Observed concentrations extrapolated to trough ranged from 360 to 1832 μg/L (median 725; mean 810, CV 52%) on 1st TDM and from 720 to 1187 μg/L (median 950; mean 940, CV 18%) on 2nd TDM cycle. Conclusions: These preliminary results suggest that TDM of imatinib using a Bayesian interpretation is able to target the recommended trough level of 1000 μg/L and to reduce the considerable differences in trough level exposure between patients (with CV decreasing from 52% to 18%). While this may simplify blood collection in daily practice, as samples do not have to be drawn exactly at trough, the largest possible interval to last drug intake yet remains preferable to avoid sampling during distribution phase leading to biased extrapolation. This encourages the evaluation of the clinical benefit of a routine TDM intervention in CML patients, which the randomized Swiss I-COME trial aims to.

Canakinumab for the treatment of acute flares in difficult-to-treat gouty arthritis: Results of a multicenter, phase II, dose-ranging study.

OBJECTIVE: To assess the efficacy and tolerability of canakinumab, a fully human anti-interleukin-1β monoclonal antibody, for the treatment of acute gouty arthritis. METHODS: In this 8-week, single-blind, double-dummy, dose-ranging study, patients with acute gouty arthritis whose disease was refractory to or who had contraindications to nonsteroidal antiinflammatory drugs and/or colchicine were randomized to receive a single subcutaneous dose of canakinumab (10, 25, 50, 90, or 150 mg; n = 143) or an intramuscular dose of triamcinolone acetonide (40 mg; n = 57). Patients assessed pain using a 100-mm visual analog scale. RESULTS: Seventy-two hours after treatment, a statistically significant dose response was observed for canakinumab. All canakinumab doses were associated with numerically less pain than triamcinolone acetonide; thus, a dose with equivalent efficacy to triamcinolone acetonide 72 hours after treatment could not be determined. The reduction from baseline in pain intensity with canakinumab 150 mg was greater than with triamcinolone acetonide 24, 48, and 72 hours after treatment (differences of -11.5 mm [P = 0.04], -18.2 mm [P = 0.002], and -19.2 mm [P < 0.001], respectively), and 4, 5, and 7 days after treatment (all P < 0.05). Canakinumab significantly reduced the risk of recurrent flares versus triamcinolone acetonide (P ≤ 0.01 for all doses) (relative risk reduction 94% for canakinumab 150 mg versus triamcinolone acetonide). The overall incidence of adverse events was similar for canakinumab (41%) and triamcinolone acetonide (42%); most were mild or moderate in severity. CONCLUSION: Our findings indicate that canakinumab 150 mg provides rapid and sustained pain relief in patients with acute gouty arthritis, and significantly reduces the risk of recurrent flares compared with triamcinolone acetonide.

A low-dose stimulation protocol using highly purified follicle-stimulating hormone can lead to high pregnancy rates in in vitro fertilization patients with polycystic ovaries who are at risk of a high ovarian response to gonadotropins.

OBJECTIVE: To study the benefits of a low-dose stimulation (LDS) protocol with purified urinary follicle-stimulating hormone in patients with polycystic ovaries who have presented previously with a very high ovarian response to a standard hMG stimulation. DESIGN: Cohort study. SETTING: Fertility center in a university hospital. PATIENT(S): Sixty-one patients involved in an IVF/ICSI program from January 1995 to December 1996. INTERVENTION(S): The patients were first stimulated with a standard protocol using hMG and presented with a very high ovarian response. These patients were then stimulated a second time using a low-dose protocol. Cryopreserved embryos were transferred in later artificial or natural cycles until to December 1999. MAIN OUTCOME MEASURE(S): Number of gonadotropin ampules; estradiol level on the day of ovulation induction; follicles, oocytes, and cryopreserved zygotes; fertilization, implantation, and pregnancy rates; and number of ovarian hyperstimulation syndromes (OHSS). RESULT(S): The number of ampules used, the estradiol level reached, and the number of oocytes obtained were significantly lower under the LDS than the standard protocol. High implantation (21.8%) and clinical pregnancy (38.4%) rates were obtained after LDS. The cumulated deliveries per cycle started and per patient were, respectively, 41.6% and 52.5%. Five patients suffered OHSS with the standard protocol, and none with the LDS. CONCLUSION(S): The LDS protocol offers a safe and efficient treatment for patients who present with echographic polycystic ovaries and are at risk of an excessive ovarian response to standard IVF stimulation protocols.

Saturable metabolism of continuous high-dose ifosfamide with mesna and GM-CSF: a pharmacokinetic study in advanced sarcoma patients. Swiss Group for Clinical Cancer Research (SAKK).

BACKGROUND: The aim of this study was to assess the pharmacology, toxicity and activity of high-dose ifosfamide mesna +/- GM-CSF administered by a five-day continuous infusion at a total ifosfamide dose of 12-18 g/m2 in adult patients with advanced sarcomas. PATIENTS AND METHODS: Between January 1991 and October 1992 32 patients with advanced or metastatic sarcoma were entered the study. Twenty-seven patients were pretreated including twenty-three with prior ifosfamide at less than 8 g/m2 total dose/cycle. In 25 patients (27 cycles) extensive pharmacokinetic analyses were performed. RESULTS: The area under the plasma concentration-time curve (AUC) for ifosfamide increased linearly with dose while the AUC's of the metabolites measured in plasma by thin-layer chromatography did not increase with dose, particularly that of the active metabolite isophosphoramide mustard. Furthermore the AUC of the inactive carboxymetabolite did not increase with dose. Interpatient variability of pharmacokinetic parameters was high. Dose-limiting toxicity was myelosuppression at 18 g/m2 total dose with grade 4 neutropenia in five of six patients and grade 4 thrombocytopenia in four of six patients. Therefore the maximum tolerated dose was considered to be 18 g/m2 total dose. There was one CR and eleven PR in twenty-nine evaluable patients (overall response rate 41%). CONCLUSION: Both the activation and inactivation pathways of ifosfamide are non-linear and saturable at high-doses although the pharmacokinetics of the parent drug itself are dose linear. Ifosfamide doses greater than 14-16 g/m2 per cycle appear to result in a relative decrease of the active metabolite isophosphoramide mustard. These data suggest a dose-dependent saturation or even inhibition of ifosfamide metabolism by increasing high dose ifosfamide and suggest the need for further metabolic studies.

Integrated Analysis of High-Resolution Gene Expression and Copy Number Profiling Identified Biallelic Deletion of CDKN2A/2B Tumor Suppressor Locus As the Most Frequent and Unique Genomic Abnormality in Diffuse Large B-Cell Lymphoma (DLBCL) with Strong Prognostic Value in Both GCB and ABC Subtypes and Not Overcome by a Dose-Intensive Immunochemotherapy Regimen Plus Rituximab. Results of a Prospective GELA Clinical Trial Program

Background and aim of the study: Genomic gains and losses play a crucial role in the development and progression of DLBCL and are closely related to gene expression profiles (GEP), including the germinal center B-cell like (GCB) and activated B-cell like (ABC) cell of origin (COO) molecular signatures. To identify new oncogenes or tumor suppressor genes (TSG) involved in DLBCL pathogenesis and to determine their prognostic values, an integrated analysis of high-resolution gene expression and copy number profiling was performed. Patients and methods: Two hundred and eight adult patients with de novo CD20+ DLBCL enrolled in the prospective multicentric randomized LNH-03 GELA trials (LNH03-1B, -2B, -3B, 39B, -5B, -6B, -7B) with available frozen tumour samples, centralized reviewing and adequate DNA/RNA quality were selected. 116 patients were treated by Rituximab(R)-CHOP/R-miniCHOP and 92 patients were treated by the high dose (R)-ACVBP regimen dedicated to patients younger than 60 years (y) in frontline. Tumour samples were simultaneously analysed by high resolution comparative genomic hybridization (CGH, Agilent, 144K) and gene expression arrays (Affymetrix, U133+2). Minimal common regions (MCR), as defined by segments that affect the same chromosomal region in different cases, were delineated. Gene expression and MCR data sets were merged using Gene expression and dosage integrator algorithm (GEDI, Lenz et al. PNAS 2008) to identify new potential driver genes. Results: A total of 1363 recurrent (defined by a penetrance > 5%) MCRs within the DLBCL data set, ranging in size from 386 bp, affecting a single gene, to more than 24 Mb were identified by CGH. Of these MCRs, 756 (55%) showed a significant association with gene expression: 396 (59%) gains, 354 (52%) single-copy deletions, and 6 (67%) homozygous deletions. By this integrated approach, in addition to previously reported genes (CDKN2A/2B, PTEN, DLEU2, TNFAIP3, B2M, CD58, TNFRSF14, FOXP1, REL...), several genes targeted by gene copy abnormalities with a dosage effect and potential physiopathological impact were identified, including genes with TSG activity involved in cell cycle (HACE1, CDKN2C) immune response (CD68, CD177, CD70, TNFSF9, IRAK2), DNA integrity (XRCC2, BRCA1, NCOR1, NF1, FHIT) or oncogenic functions (CD79b, PTPRT, MALT1, AUTS2, MCL1, PTTG1...) with distinct distribution according to COO signature. The CDKN2A/2B tumor suppressor locus (9p21) was deleted homozygously in 27% of cases and hemizygously in 9% of cases. Biallelic loss was observed in 49% of ABC DLBCL and in 10% of GCB DLBCL. This deletion was strongly correlated to age and associated to a limited number of additional genetic abnormalities including trisomy 3, 18 and short gains/losses of Chr. 1, 2, 19 regions (FDR < 0.01), allowing to identify genes that may have synergistic effects with CDKN2A/2B inactivation. With a median follow-up of 42.9 months, only CDKN2A/2B biallelic deletion strongly correlates (FDR p.value < 0.01) to a poor outcome in the entire cohort (4y PFS = 44% [32-61] respectively vs. 74% [66-82] for patients in germline configuration; 4y OS = 53% [39-72] vs 83% [76-90]). In a Cox proportional hazard prediction of the PFS, CDKN2A/2B deletion remains predictive (HR = 1.9 [1.1-3.2], p = 0.02) when combined with IPI (HR = 2.4 [1.4-4.1], p = 0.001) and GCB status (HR = 1.3 [0.8-2.3], p = 0.31). This difference remains predictive in the subgroup of patients treated by R-CHOP (4y PFS = 43% [29-63] vs. 66% [55-78], p=0.02), in patients treated by R-ACVBP (4y PFS = 49% [28-84] vs. 83% [74-92], p=0.003), and in GCB (4y PFS = 50% [27-93] vs. 81% [73-90], p=0.02), or ABC/unclassified (5y PFS = 42% [28-61] vs. 67% [55-82] p = 0.009) molecular subtypes (Figure 1). Conclusion: We report for the first time an integrated genetic analysis of a large cohort of DLBCL patients included in a prospective multicentric clinical trial program allowing identifying new potential driver genes with pathogenic impact. However CDKN2A/2B deletion constitutes the strongest and unique prognostic factor of chemoresistance to R-CHOP, regardless the COO signature, which is not overcome by a more intensified immunochemotherapy. Patients displaying this frequent genomic abnormality warrant new and dedicated therapeutic approaches.

Is Less Chemotherapy Detrimental in Adults with Philadelphia Chromosome (Ph)-Positive Acute Lymphoblastic Leukemia (ALL) Treated with High-Dose Imatinib? Results of the Prospective Randomized Graaph-2005 Study

Aim: To compare a less intensive regimen based on high-dose imatinib (IM) to an intensive IM/HyperCVAD regimen in adults with Ph+ ALL, in terms of early response and outcome after stem cell transplantation (SCT). Methods: Patients aged 18-60 years with previously untreated Ph+ ALL not evolving from chronic myeloid leukemia were eligible if no contra-indication to chemotherapy and SCT (ClinicalTrials.gov ID, NCT00327678). After a steroid prephase allowing Ph and/or BCR-ABL diagnosis, cycle 1 differed between randomization arms. In arm A (IM-based), IM was given at 800 mg on day 1-28, combined with vincristine (2 mg, day 1, 8, 15, 22) and dexamethasone (40 mg, day 1-2, 8-9, 15-16, and 22-23) only. In arm B (IM/HyperCVAD), IM was given at 800 mg on day 1-14, combined with adriamycin (50 mg/m2, day 4), cyclophosphamide (300 mg/m2/12h, day 1, 2, 3), vincristine (2 mg, day 4 and 11), and dexamethasone (40 mg, day 1-4 and 11-14). All patients received a cycle 2 combining high-dose methotrexate (1 g/m2, day 1) and AraC (3 g/m2/12h, day 2 and 3) with IM at 800 mg on day 1-14, whatever their response. Four intrathecal infusions were given during this induction/consolidation period. Minimal residual disease (MRD) was centrally evaluated by quantitative RQ-PCR after cycle 1 (MRD1) and cycle 2 (MRD2). Major MRD response was defined as BCR-ABL/ABL ratio <0.1%. Then, all patients were to receive allogeneic SCT using related or unrelated matched donor stem cells or autologous SCT if no donor and a major MRD2 response. IM/chemotherapy maintenance was planned after autologous SCT. In the absence of SCT, patients received alternating cycles 1 (as in arm B) and cycles 2 followed by maintenance, like in the published IM/HyperCVAD regimen. The primary objective was non-inferiority of arm A in term of major MRD2 response. Secondary objectives were CR rate, SCT rate, treatment- and transplant-related mortality, relapse-free (RFS), event-free (EFS) and overall (OS) survival. Results: Among the 270 patients randomized between May 2006 and August 2011, 265 patients were evaluable for this analysis (133 arm A, 132 arm B; median age, 47 years; median follow-up, 40 months). Main patient characteristics were well-balanced between both arms. Due to higher induction mortality in arm B (9 versus 1 deaths; P=0.01), CR rate was higher in the less intensive arm A (98% versus 89% after cycle 1 and 98% versus 91% after cycle 2; P= 0.003 and 0.006, respectively). A total of 213 and 205 patients were evaluated for bone marrow MRD1 and MRD2. The rates of patients reaching major MRD response and undetectable MRD were 45% (44% arm A, 46% arm B; P=0.79) and 10% (in both arms) at MRD1 and 66% (68% arm A, 63.5% arm B; P=0.56) and 25% (28% arm A, 22% arm B; P=0.33) at MRD2, respectively. The non-inferiority primary endpoint was thus demonstrated (P= 0.002). Overall, EFS was estimated at 42% (95% CI, 35-49) and OS at 51% (95% CI, 44-57) at 3 years, with no difference between arm A and B (46% versus 38% and 53% versus 49%; P=0.25 and 0.61, respectively). Of the 251 CR patients, 157 (80 arm A, 77 arm B) and 34 (17 in both arms) received allogeneic and autologous SCT in first CR, respectively. Allogeneic transplant-related mortality was similar in both arms (31.5% versus 22% at 3 years; P=0.51). Of the 157 allografted patients, 133 had MRD2 evaluation and 89 had MRD2 <0.1%. In these patients, MRD2 did not significantly influence post-transplant RFS and OS, either when tested with the 0.1% cutoff or as a continuous log covariate. Of the 34 autografted patients, 31 had MRD2 evaluation and, according to the protocol, 28 had MRD2 <0.1%. When restricting the comparison to patients achieving major MRD2 response and with the current follow-up, a trend for better results was observed after autologous as compared to allogeneic SCT (RFS, 63% versus 49.5% and OS, 69% versus 58% at 3 years; P=0.35 and P=0.08, respectively). Conclusions: In adults, the use of TK inhibitors (TKI) has markedly improved the results of Ph+ ALL therapy, now close to those observed in Ph-negative ALL. We demonstrated here that chemotherapy intensity may be safely reduced when associated with high-dose IM. We will further explore this TKI-based strategy using nilotinib prior to SCT in our next GRAAPH-2013 trial. The trend towards a better outcome after autologous compared to allogeneic SCT observed in MRD responders validates MRD as an important early surrogate endpoint for treatment stratification and new drug investigation in this disease.

A Dose-Response Strategy Reveals Differences between Normal-Weight and Obese Men in Their Metabolic and Inflammatory Responses to a High-Fat Meal.

A dose-response strategy may not only allow investigation of the impact of foods and nutrients on human health but may also reveal differences in the response of individuals to food ingestion based on their metabolic health status. In a randomized crossover study, we challenged 19 normal-weight (BMI: 20-25 kg/m(2)) and 18 obese (BMI: >30 kg/m(2)) men with 500, 1000, and 1500 kcal of a high-fat (HF) meal (60.5% energy from fat). Blood was taken at baseline and up to 6 h postprandially and analyzed for a range of metabolic, inflammatory, and hormonal variables, including plasma glucose, lipids, and C-reactive protein and serum insulin, glucagon-like peptide-1, interleukin-6 (IL-6), and endotoxin. Insulin was the only variable that could differentiate the postprandial response of normal-weight and obese participants at each of the 3 caloric doses. A significant response of the inflammatory marker IL-6 was only observed in the obese group after ingestion of the HF meal containing 1500 kcal [net incremental AUC (iAUC) = 22.9 ± 6.8 pg/mL × 6 h, P = 0.002]. Furthermore, the net iAUC for triglycerides significantly increased from the 1000 to the 1500 kcal meal in the obese group (5.0 ± 0.5 mmol/L × 6 h vs. 6.0 ± 0.5 mmol/L × 6 h; P = 0.015) but not in the normal-weight group (4.3 ± 0.5 mmol/L × 6 h vs. 4.8 ± 0.5 mmol/L × 6 h; P = 0.31). We propose that caloric dose-response studies may contribute to a better understanding of the metabolic impact of food on the human organism. This study was registered at clinicaltrials.gov as NCT01446068.

When "enough" is not enough: new perspectives on optimal methadone maintenance dose.

Some methadone maintenance treatment (MMT) programs prescribe inadequate daily methadone doses. Patients complain of withdrawal symptoms and continue illicit opioid use, yet practitioners are reluctant to increase doses above certain arbitrary thresholds. Serum methadone levels (SMLs) may guide practitioners dosing decisions, especially for those patients who have low SMLs despite higher methadone doses. Such variation is due in part to the complexities of methadone metabolism. The medication itself is a racemic (50:50) mixture of 2 enantiomers: an active "R" form and an essentially inactive "S" form. Methadone is metabolized primarily in the liver, by up to five cytochrome P450 isoforms, and individual differences in enzyme activity help explain wide ranges of active R-enantiomer concentrations in patients given identical doses of racemic methadone. Most clinical research studies have used methadone doses of less than 100 mg/day [d] and have not reported corresponding SMLs. New research suggests that doses ranging from 120 mg/d to more than 700 mg/d, with correspondingly higher SMLs, may be optimal for many patients. Each patient presents a unique clinical challenge, and there is no way of prescribing a single best methadone dose to achieve a specific blood level as a "gold standard" for all patients. Clinical signs and patient-reported symptoms of abstinence syndrome, and continuing illicit opioid use, are effective indicators of dose inadequacy. There does not appear to be a maximum daily dose limit when determining what is adequately "enough" methadone in MMT.

Comparative socio-economic evaluation of IBD patients with and without infliximab maintenance therapy

Background: The anti-TNFα agent Infliximab (IFX) is used for the treatment of moderate to severe inflammatory bowel disease (IBD) with insufficient response to conventional immunomodulator therapy. IFX maintenance therapy is expensive and it is unknown if indirect costs (eg. by loss of work productivity) can be reduced by this therapy. Goal: to evaluate the direct and indirect costs of an IBD patient cohort under maintenance IFX compared to a cohort under "conventional" immunomodulator therapy. Methods: Direct and indirect costs of an IBD cohort under IFX and a reference cohort (similar disease activity and location) under conventional immunomodulator therapy (Azathioprine, or 6-MP, or MTX) were retrospectively evaluated over 12 months (January to December 2008). Results: 54 IFX-patients (24f/30m, 37 CD, 10 UC, 7 IC) and 71 non-IFX-patients (38f/33m, 56 CD, 12 UC, 3 IC) were included. IFX patients were younger than non-IFX patients (36 vs. 47 years, P = 0.0003). The mean duration of inpatient stay in hospital (23 in IFX vs. 21 days for non-IFX, P = 0.909) and the hospitalization costs (7,692 in IFX vs. 4,179 SFr for non-IFX, P = 0.4540) did not differ. IFX-patients had significantly more frequently specialist outpatient consultations (8 vs. 4, P < 0.001) and outpatient-related costs (3,633 vs. 2,186 SFr, P <0.001). Total costs for all diagnostic procedures (blood work, endoscopies, radiology) were higher in the IFXcohort (2,265 vs. 1,164 SFr, P < 0.001). Sixty-five percent of IFX-patients had a 100% job employment compared to 80% in the non-IFX cohort (P = 0.001). Conclusions: The direct and indirect costs of maintenance IFX-treated IBD patients are higher compared to IBD patients under conventional immunomodulators. Care should be taken not only to judge the costs as the IFX treated population may represent a cohort with more aggressive disease phenotype, furthermore, quality of life aspects were not assessed.

Oral administration of a low dose of midazolam (75 microg) as an in vivo probe for CYP3A activity.

OBJECTIVE: We investigated whether the oral administration of a low dose (75 micro g) of midazolam, a CYP3A probe, can be used to measure the in vivo CYP3A activity. METHODS: Plasma concentrations of midazolam, 1'OH-midazolam and 4'OH-midazolam were measured after the oral administration of 7.5 mg and 75 micro g midazolam in 13 healthy subjects without medication, in four subjects pretreated for 2 days with ketoconazole (200 mg b.i.d.), a CYP3A inhibitor, and in four subjects pretreated for 4 days with rifampicin (450 mg q.d.), a CYP3A inducer. RESULTS: After oral administration of 75 micro g midazolam, the 30-min total (unconjugated + conjugated) 1'OH-midazolam/midazolam ratios measured in the groups without co-medication, with ketoconazole and with rifampicin were (mean+/-SD): 6.23+/-2.61, 0.79+/-0.39 and 56.1+/-12.4, respectively. No side effects were reported by the subjects taking this low dose of midazolam. Good correlations were observed between the 30-min total 1'OH-midazolam/midazolam ratio and midazolam clearance in the group without co-medication (r(2)=0.64, P<0.001) and in the three groups taken together (r(2)=0.91, P<0.0001). Good correlations were also observed between midazolam plasma levels and midazolam clearance, measured between 1.5 h and 4 h. CONCLUSION: A low oral dose of midazolam can be used to phenotype CYP3A, either by the determination of total 1'OH-midazolam/midazolam ratios at 30 min or by the determination of midazolam plasma levels between 1.5 h and 4 h after its administration.

Influence of the timing of low-dose aspirin on tolerability of prolonged-release nicotinic acid in patients at elevated cardiovascular risk

OBJECTIVES: To investigate the effect of low-dose aspirin administered in the morning or evening on the rate of discontinuation of prolonged-release nicotinic acid (Niaspan) due to flushing in patients at elevated cardiovascular risk. RESEARCH DESIGN AND METHODS: This was an observational, non-interventional study in patients at elevated cardiovascular risk due to cardiovascular disease or type 2 diabetes. Patients received prolonged-release nicotinic acid and aspirin under the usual care of their physician for 15 weeks. MAIN OUTCOME MEASURES: The main outcome measure was the rate of treatment discontinuation for flushing. Other adverse drug reactions (ADRs) were also recorded. Lipid parameters were also measured. RESULTS: The patient population included 539 subjects (70% male); 36% had type 2 diabetes, 80% had prior cardiovascular disease, and 37% had a family history of cardiovascular disease. The rate of treatment discontinuation due to flushing did not differ (p = 0.3375) between the morning aspirin group (10.6%) and the evening aspirin group (13.8%). The overall incidence of flushing was 57%. Most flushes were of mild or moderate severity and decreases occurred over time in both frequency and intensity. ADRs unrelated to flushing occurred in 6.6% of the morning aspirin group and 7.4% of the evening aspirin group. HDL-cholesterol increased by +21.3% in the overall population, together with moderate improvements in other lipid parameters. CONCLUSIONS: Flushing was the most common ADR with prolonged-release nicotinic acid treatment, as expected. The timing of aspirin administration did not influence the rate of treatment discontinuations for flushing. Marked increases in HDL-cholesterol were observed.

Safe and effective variability-a criterion for dose individualization.

BACKGROUND: : A primary goal of clinical pharmacology is to understand the factors that determine the dose-effect relationship and to use this knowledge to individualize drug dose. METHODS: : A principle-based criterion is proposed for deciding among alternative individualization methods. RESULTS: : Safe and effective variability defines the maximum acceptable population variability in drug concentration around the population average. CONCLUSIONS: : A decision on whether patient covariates alone are sufficient, or whether therapeutic drug monitoring in combination with target concentration intervention is needed, can be made by comparing the remaining population variability after a particular dosing method with the safe and effective variability.

Pharmacokinetic and pharmacodynamic analysis of efavirenz dose reduction using an in vitro-in vivo extrapolation model.

The pharmacokinetics (PK) of efavirenz (EFV) is characterized by marked interpatient variability that correlates with its pharmacodynamics (PD). In vitro-in vivo extrapolation (IVIVE) is a "bottom-up" approach that combines drug data with system information to predict PK and PD. The aim of this study was to simulate EFV PK and PD after dose reductions. At the standard dose, the simulated probability was 80% for viral suppression and 28% for central nervous system (CNS) toxicity. After a dose reduction to 400 mg, the probabilities of viral suppression were reduced to 69, 75, and 82%, and those of CNS toxicity were 21, 24, and 29% for the 516 GG, 516 GT, and 516 TT genotypes, respectively. With reduction of the dose to 200 mg, the probabilities of viral suppression decreased to 54, 62, and 72% and those of CNS toxicity decreased to 13, 18, and 20% for the 516 GG, 516 GT, and 516 TT genotypes, respectively. These findings indicate how dose reductions might be applied in patients with favorable genetic characteristics.