Quality Control of Busulfan Plasma Quantitation, Modeling, and Dosing: An Interlaboratory Proficiency Testing Program.

BACKGROUND: Personalizing busulfan doses to target a narrow plasma exposure has improved the efficacy and lowered the toxicity of busulfan-based conditioning regimens used in hematopoietic cell transplant. Regional regulations guide interlaboratory proficiency testing for busulfan concentration quantification and monitoring. To date, there have been no comparisons of the busulfan pharmacokinetic modeling and dose recommendation protocols used in these laboratories. Here, in collaboration with the Dutch Association for Quality Assessment in Therapeutic Drug Monitoring and Clinical Toxicology, a novel interlaboratory proficiency program for the quantitation in plasma, pharmacokinetic modeling, and dosing of busulfan was designed. The methods and results of the first 2 rounds of this proficiency testing are described herein. METHODS: A novel method was developed to stabilize busulfan in N,N-dimethylacetamide, which allowed shipping of the proficiency samples without dry ice. In each round, participating laboratories reported their results for 2 proficiency samples (one low and one high busulfan concentrations) and a theoretical case assessing their pharmacokinetic modeling and dose recommendations. All participants were blinded to the answers; descriptive statistics were used to evaluate their overall performance. The guidelines suggested that answers within ±15% for busulfan concentrations and ±10% for busulfan plasma exposure and dose recommendation were to be considered accurate. RESULTS: Of the 4 proficiency samples evaluated, between 67% and 85% of the busulfan quantitation results were accurate (ie, within 85%-115% of the reference value). The majority (88% round #1; 71% round #2) of the dose recommendation answers were correct. CONCLUSIONS: A proficiency testing program by which laboratories are alerted to inaccuracies in their quantitation, pharmacokinetic modeling, and dose recommendations for busulfan in hematopoietic cell transplant recipients was developed. These rounds of proficiency testing suggests that additional educational efforts and proficiency rounds are needed to ensure appropriate busulfan dosing.

Harmonization of Busulfan Plasma Exposure Unit (BPEU): A Community-Initiated Consensus Statement.

Busulfan therapeutic drug monitoring (TDM) is often used to achieve target plasma exposures. Variability in busulfan plasma exposure units (BPEU) is a potential source for misinterpretation of publications and protocols and is a barrier to data capture by hematopoietic cell transplantation (HCT) registry databases. We sought to harmonize to a single BPEU for international use. Using Delphi consensus methodology, iterative surveys were sent to an increasing number of relevant clinical stakeholders. In survey 1, 14 stakeholders were asked to identify ideal properties of a BPEU. In survey 2, 52 stakeholders were asked (1) to evaluate BPEU candidates according to ideal BPEU properties established by survey 1 and local position statements for TDM and (2) to identify potential facilitators and barriers to adoption of the harmonized BPEU. The most frequently used BPEU identified, in descending order, were area under the curve (AUC) in µM × min, AUC in mg × h/L, concentration at steady state (Css) in ng/mL, AUC in µM × h, and AUC in µg × h/L. All respondents conceptually agreed on the ideal properties of a BPEU and to adopt a harmonized BPEU. Respondents were equally divided between selecting AUC in µM × min versus mg × h/L for harmonization. AUC in mg × h/L was finally selected as the harmonized BPEU, because it satisfied most of the survey-determined ideal properties for the harmonized BPEU and is read easily understood in the clinical practice environment. Furthermore, 10 major professional societies have endorsed AUC in mg × h/L as the harmonized unit for reporting to HCT registry databases and for use in future protocols and publications.

Efficacy of Pharmacokinetics-Directed Busulfan, Cyclophosphamide, and Etoposide Conditioning and Autologous Stem Cell Transplantation for Lymphoma: Comparison of a Multicenter Phase II Study and CIBMTR Outcomes.

Busulfan, cyclophosphamide, and etoposide (BuCyE) is a commonly used conditioning regimen for autologous stem cell transplantation (ASCT). This multicenter, phase II study examined the safety and efficacy of BuCyE with individually adjusted busulfan based on preconditioning pharmacokinetics. The study initially enrolled Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) patients ages 18 to 80 years but was amended due to high early treatment-related mortality (TRM) in patients > 65 years. BuCyE outcomes were compared with contemporaneous recipients of carmustine, etoposide, cytarabine, and melphalan (BEAM) from the Center for International Blood and Marrow Transplant Research. Two hundred seven subjects with HL (n = 66) or NHL (n = 141) were enrolled from 32 centers in North America, and 203 underwent ASCT. Day 100 TRM for all subjects (n = 203), patients > 65 years (n = 17), and patients ≤ 65 years (n = 186) were 4.5%, 23.5%, and 2.7%, respectively. The estimated rates of 2-year progression-free survival (PFS) were 33% for HL and 58%, 77%, and 43% for diffuse large B cell lymphoma (DLBCL; n = 63), mantle cell lymphoma (MCL; n = 29), and follicular lymphoma (FL; n = 23), respectively. The estimated rates of 2-year overall survival (OS) were 76% for HL and 65%, 89%, and 89% for DLBCL, MCL, and FL, respectively. In the matched analysis rates of 2-year TRM were 3.3% for BuCyE and 3.9% for BEAM, and there were no differences in outcomes for NHL. Patients with HL had lower rates of 2-year PFS with BuCyE, 33% (95% CI, 21% to 46%), than with BEAM, 59% (95% CI, 52% to 66%), with no differences in TRM or OS. BuCyE provided adequate disease control and safety in B cell NHL patients ≤ 65 years but produced worse PFS in HL patients when compared with BEAM.

Safety and efficacy of targeted-dose busulfan and bortezomib as a conditioning regimen for patients with relapsed multiple myeloma undergoing a second autologous blood progenitor cell transplantation.

Patients with multiple myeloma (MM) who relapse after autologous transplantation have limited therapeutic options. We conducted a prospective, multicenter, phase IIa study to investigate the safety and efficacy of i.v. busulfan (Bu) in combination with bortezomib as a conditioning regimen for a second autotransplantation. Because a safe Bu exposure was unknown in patients receiving this combination, Bu was initially targeted to a total area under the concentration-time curve (AUC) of 20,000 µM × minute. As no concentration-limiting toxicity was observed in 6 patients, this Bu exposure was utilized in the following treatment cohort (n = 24). Individualized Bu dose, based on test dose .8 mg/kg pharmacokinetics (PK), was administered daily for 4 consecutive days starting 5 days before transplantation, followed by a single dose of bortezomib (1.3 mg/m(2)) 1 day before transplantation. The total mean dose of i.v. Bu (including the test dose and 4-day administration) was 14.2 mg/kg (standard deviation = 2.48; range, 8.7 to 19.2). Confirmatory PK demonstrated that only 2 of 30 patients who underwent transplantation were dosed outside the Bu AUC target and dose adjustments were made for the last 2 doses of i.v. Bu. The median age was 59 years (range, 48 to 73). Median time from first to second transplantation was 28.0 months (range, 12 to 119). Of 26 evaluable patients, 10 patients attained a partial response (PR) or better at 3 months after transplantation, with 2 patients attaining a complete response. At 6 months after transplantation, 5 of 12 evaluable patients had maintained or improved their disease status. Median progression-free survival was 191 days, whereas median overall survival was not reached during the study period. The most common grade 3 and 4 toxicities were febrile neutropenia (50.0%) and stomatitis (43.3%). One transplantation-related death was observed. A combination of dose-targeted i.v. Bu and bortezomib induced PR or better in one third of patients with MM who underwent a second autotransplantation, with acceptable toxicity.

Accurate targeting of daily intravenous busulfan with 8-hour blood sampling in hospitalized adult hematopoietic cell transplant recipients.

Daily intravenous (i.v.) busulfan is increasingly being used in hematopoietic cell transplantation (HCT) conditioning regimens. Intravenous busulfan doses administered at the traditional frequency of every 6 hours can be targeted ((T)Bu) to a patient-specific concentration at steady state (C(ss)) using therapeutic drug monitoring (TDM). In this report, we describe our experiences with TDM of daily i.v. busulfan in an adult population, with the specific aims of (1) evaluating covariates associated with busulfan clearance, and (2) assessing the feasibility of TDM for outpatient administration of daily (T)Bu with pharmacokinetic sampling over 6 hours. A retrospective pharmacokinetic analysis was conducted in 87 adults receiving daily (T)Bu as part of cyclophosphamide followed by (T)BU (CY/(T)BU), fludarabine monophosphate (fludarabine) followed by (T)BU, or (T)BU concurrent with fludarabine conditioning. The desired C(ss) was achieved in 85% of patients receiving daily i.v. busulfan. Busulfan clearance was not associated with sex or age, but was associated with the day of dosing and conditioning regimen (P = .0016). In patients receiving CY/(T)BU, no differences in clearance were found between dosing days (P > .36); however, clearance decreased significantly in patients receiving fludarabine-based regimens (P = .0016). Busulfan clearance and C(ss) estimates from pharmacokinetic sampling over 8, 11, or 24 hours were comparable (P > .4). However, pharmacokinetic modeling of individual patient concentration-time data over 6 hours could not reliably estimate busulfan clearance or C(ss).

Graft-versus-host Disease Prophylaxis With Abatacept Reduces Severe Acute Graft-versus-host Disease in Allogeneic Hematopoietic Stem Cell Transplant for Beta-thalassemia Major With Busulfan, Fludarabine, and Thiotepa.

BACKGROUND: We hypothesized that the addition of 4 doses of abatacept to our standard acute graft-versus-host disease (GVHD) prophylaxis would reduce the incidence of day +100 severe acute GVHD in children with transfusion-dependent beta-thalassemia major undergoing a myeloablative allogeneic hematopoietic stem cell transplant (HSCT), without impacting engraftment. METHODS: Twenty-four children with beta-thalassemia major received abatacept at a dose of 10 mg/kg intravenously on days -1, +5, +14, and +28 after HSCT in addition to calcineurin inhibitors and methylprednisolone. Outcomes were compared to 8 beta-thalassemia patients who received standard acute GVHD prophylaxis. RESULTS: There was no difference in engraftment between the 2 groups. No patient had grades III-IV acute GVHD by day +100 in the abatacept cohort compared with 50% in the standard acute GVHD prophylaxis group (P = 0.001). Viral reactivation occurred in 5 children in the standard acute GVHD cohort and in 20 children in the abatacept cohort (P = 0.2). Thalassemia-free survival after HSCT was 100% in the abatacept cohort compared to 62.5% in the standard cohort at last follow-up (P = 0.007). CONCLUSIONS: Adding abatacept to our routine GVHD prophylaxis reduced the incidence of day +100 severe acute GVHD without impacting engraftment or survival.

Lopinavir/ritonavir dosage form affects quality of life during monotherapy in HIV-positive adults.

This was a single-center, open-label study of lopinavir/ritonavir (LPV/r) single-agent therapy in antiretroviral-naive, HIV-infected participants initiating therapy with twice-daily soft-gelatin capsules (SGC) and switched to tablets after ≥4 weeks. The objective was to evaluate quality of life and tolerability of the 2 formulations. Participants quality of life, depression, and tolerability were measured using the Medical Outcomes Study-HIV (MOS-HIV), Modified Global Condition Improvement (GCI), and Center for Epidemiologic Studies-Depression (CES-D), prior to and 4 weeks following switch. MOS-HIV showed significant improvements in general health perception (+6 (16), mean (SD); P = .047) and role functioning (+8 (19), mean (SD); P = .023) post-switch. GCI showed significant improvement in ease of taking medications with tablets (56.7% vs 83.3%; P = .021). No change was observed in CES-D. Tolerability improved in 47%. Reported diarrhea (grade 2) was higher during SGC (33.3% vs3.3%; P = .004). Quality-of-life measures, tolerability, and diarrhea improved with the LPV/r tablet formulation compared to SGC in HIV-positive patients not receiving other antiretroviral therapy (ART).

Genital tract, cord blood, and amniotic fluid exposures of seven antiretroviral drugs during and after pregnancy in human immunodeficiency virus type 1-infected women.

The objective of the study was to measure antiretroviral exposures in four physiological compartments during pregnancy, delivery, and postpartum. This prospective, open-label, longitudinal study collected paired blood plasma (BP) and genital tract (GT) aspirates antepartum, at delivery, and up to 12 weeks postpartum. Antiretroviral cord BP and amniotic fluid concentrations were also measured. Drug concentrations were analyzed by validated high-performance liquid chromatography/UV and liquid chromatography/tandem mass spectrometry methods, with secondary compartment concentrations presented as the percentage of BP. Fourteen women taking lamivudine plus zidovudine and either lopinavir-ritonavir (n = 7), nelfinavir (n = 6), or nevirapine (n = 1) were enrolled; four also received tenofovir. GT penetration relative to BP was highest for the nucleoside reverse transcriptase inhibitors compared to the protease inhibitors and nevirapine. Only antepartum nelfinavir GT penetration was significantly higher than in the second trimester (geometric mean ratio [GMR], 179.3) or third trimester (GMR, 41.9). Compared to nonpregnant historical controls, antepartum GT penetration was significantly lower (P < 0.05) for zidovudine (GMR, 0.25) and lopinavir (GMR, 0.03); postpartum lopinavir GT penetration continued to be significantly lower (GMR, 0.27). Cord BP exposures were highest for lamivudine and tenofovir (> or = 100%), with cord BP levels of the remaining drugs ranging from 49 to 86% of that of the respective BP level. Amniotic exposures for lamivudine, zidovudine, tenofovir, and nelfinavir were > or = 100%, nevirapine exposure was 53%, and lopinavir and ritonavir exposures were < or = 6% that of BP. We conclude that GT, cord BP, and amniotic fluid exposures vary within and between antiretroviral drug classes and biologic sites. Measurement of antiretroviral exposure in maternal genital secretions, cord BP, and amniotic fluid may be needed to identify signals of subtherapeutic or supratherapeutic drug exposure.

Use/misuse of over-the-counter medications and associated adverse drug events among HIV-infected patients.

BACKGROUND: Self-medication practices and polypharmacy are common among human immunodeficiency virus (HIV)-infected patients. Inappropriate use of over-the-counter (OTC) medications potentiates the risk for drug misuse and adverse drug events (ADEs). OBJECTIVES: To investigate use and misuse of OTC medications in HIV-infected patients and determine related ADEs. METHODS: A nonexperimental cross-sectional field study design was used. Study subjects were HIV-infected patients from a local HIV clinic in Houston, TX. Information on subject demographics, OTC medication use, and ADEs experienced were obtained using combined self-administered questionnaire and personal interview techniques. Misuse was divided into 3 categories: strength/frequency misuse, length misuse, and condition misuse. Data were analyzed using descriptive and Chi-square analyses. RESULTS: A total of 215 completed surveys were obtained, with a net response rate of 63.6%. The mean (+/-SD) age of the respondents was 45 (+/-8.32) years and 69% were males. Analgesics/antipyretics (64.2%) were the most commonly used OTC medications of which nonsteroidal agents accounted for the greatest proportion (38.4%). Of the respondents, 80 (37.2%) misused OTC medications. The highest incidence occurred in length misuse (46.3%), followed by strength/frequency misuse (45.6%), and condition misuse (8.1%). Categories of misuse overlapped in 30 cases (20.1%). Thirty-six (16.7%) participants experienced at least one or more ADEs related to OTC medication use/misuse. Occurrence of ADEs was significantly higher in patients who misused OTC medications compared with those who did not (P < .05). CONCLUSIONS: Analgesics/antipyretics were the most commonly used OTC medications by HIV-infected patients. The incidence of misuse and ADEs associated with OTC medications were documented with the sample. Keeping in mind the limitations of study design, our findings suggest that misuse of OTC medications in HIV-infected patients may increase the incidence of ADEs experienced.

Antiretroviral drug exposure in the female genital tract: implications for oral pre- and post-exposure prophylaxis.

OBJECTIVES: To describe first dose and steady state antiretroviral drug exposure in the female genital tract. DESIGN: Non-blinded, single center, open-label pharmacokinetic study in HIV-infected women. METHOD: Twenty-seven women initiating combination antiretroviral therapy underwent comprehensive blood plasma and cervicovaginal fluid sampling for drug concentrations during the first dose of antiretroviral therapy and at steady-state. Drug concentrations were measured by validated HPLC/UV or HPLC-MS/MS methods. Pharmacokinetic parameters were estimated for 11 drugs by non-compartmental analysis. Descriptive statistics and 95% confidence intervals were generated using Intercooled STATA Release 8.0 (Stata Corporation, College Station, Texas, USA). RESULTS: For all antiretroviral drugs, genital tract concentrations were detected rapidly after the first dose. Drugs were stratified according to the genital tract concentrations achieved relative to blood plasma. Median rank order of highest to lowest genital tract concentrations relative to blood plasma at steady state were: lamivudine (concentrations achieved were 411% greater than blood plasma), emtricitabine (395%), zidovudine (235%) tenofovir (75%), ritonavir (26%), didanosine (21%), atazanavir (18%), lopinavir (8%), abacavir (8%), stavudine (5%), and efavirenz (0.4%). CONCLUSIONS: This is the first study to comprehensively evaluate antiretroviral drug exposure in the female genital tract. These findings support the use of lamivudine, zidovudine, tenofovir and emtricitabine as excellent pre-exposure/post-exposure prophylaxis (PrEP/PEP) candidates. Atazanavir and lopinavir might be useful agents for these applications due to favorable therapeutic indices, despite lower genital tract concentrations. Agents such as stavudine, abacavir, and efavirenz that achieve genital tract exposures less than 10% of blood plasma are less attractive PrEP/PEP candidates.

Phase I Study of Veliparib (ABT-888) Combined with Cisplatin and Vinorelbine in Advanced Triple-Negative Breast Cancer and/or BRCA Mutation-Associated Breast Cancer.

PURPOSE: Cisplatin is synergistic with vinorelbine and the PARP inhibitor veliparib, and has antineoplastic activity in triple-negative breast cancer (TNBC) and BRCA mutation-associated breast cancer. This phase I study assessed veliparib with cisplatin and vinorelbine. EXPERIMENTAL DESIGN: A 3+3 dose-escalation design evaluated veliparib administered twice daily for 14 days with cisplatin (75 mg/m(2) day 1) and vinorelbine (25 mg/m(2) days 1, 8) every 21 days, for 6 to 10 cycles, followed by veliparib monotherapy. Pharmacokinetics, measurement of poly(ADP-ribose) in peripheral blood mononuclear cells, and preliminary efficacy were assessed. IHC and gene-expression profiling were evaluated as potential predictors of response. RESULTS: Forty-five patients enrolled in nine dose cohorts plus five in an expansion cohort at the highest dose level and recommended phase II dose, 300 mg twice daily. The MTD of veliparib was not reached. Neutropenia (36%), anemia (30%), and thrombocytopenia (12%) were the most common grade 3/4 adverse events. Best overall response for 48 patients was radiologic response with 9-week confirmation for 17 (35%; 2 complete, 15 partial), and stable disease for 21 (44%). Germline BRCA mutation presence versus absence was associated with 6-month progression-free survival [PFS; 10 of 14 (71%) vs. 8 of 27 (30%), mid-P = 0.01]. Median PFS for all 50 patients was 5.5 months (95% confidence interval, 4.1-6.7). CONCLUSIONS: Veliparib at 300 mg twice daily combined with cisplatin and vinorelbine is well tolerated with encouraging response rates. A phase II randomized trial is planned to assess veliparib's contribution to cisplatin chemotherapy in metastatic TNBC and BRCA mutation-associated breast cancer. Clin Cancer Res; 22(12); 2855-64. ©2016 AACR.

Symposium on roles of and cooperation between academic- and practice-based pharmacy clinicians.

PURPOSE: The findings of an academic symposium as they relate to the history and role of the academic pharmacy clinician, the strengths and limitations of the academic pharmacy clinician model, and the framework for future synergistic work relations among clinical pharmacy practitioners are summarized. SUMMARY: On April 23, 2008, a symposium was convened to bring key thought leaders together to discuss the relationship of the academic-based pharmacy clinician and the practice-based pharmacy clinician. Participants included clinical faculty and administrators from two colleges of pharmacy, practice-based clinical pharmacists and pharmacy managers from seven health care institutions, and representatives from the American Association of Colleges of Pharmacy, the American College of Clinical Pharmacy, and the American Society of Health-System Pharmacists. Symposium participants discussed the roles and expectations of clinical pharmacists based on primary affiliation within the contemporary practice model for academic- and practice-based pharmacy clinicians and identified sources of conflict for academic- and practice-based pharmacy clinicians. Symposium participants agreed that in order to succeed, the academic-based and the practice-based pharmacy clinicians must function in a true partnership as each individual has strengths, resources, and benefits to bring to the relationship. Furthermore, knowledge, consideration, and an understanding of the potentially different goals and objectives of each institution are critical. CONCLUSION: A symposium attended by clinical faculty members and administrators from two colleges of pharmacy, practice-based clinical pharmacists and pharmacy managers from seven health care institutions, and representatives from three national pharmacy organizations was conducted to discuss the roles of and cooperation between academic- and practice-based pharmacy clinicians.

Significant publications on infectious diseases pharmacotherapy in 2009.

PURPOSE: Significant publications on infectious diseases (ID) pharmacotherapy in 2009 are summarized. SUMMARY: On December 31, 2009, the Houston Infectious Diseases Network amassed a list of articles identified as having a significant impact on ID pharmacotherapy. Articles selected were published between January 1, 2009, and December 31, 2009, in prominent, peer-reviewed journals. Articles were selected based on their perceived potential impact on pharmacy practice in ID, human immunodeficiency virus (HIV), or acquired immune deficiency syndrome (AIDS). A list of 45 articles not related to HIV infection and 17 articles related to HIV infection was distributed to members of the Society of Infectious Diseases Pharmacists (SIDP) via an Internet survey. Members were asked to select the 10 publications (from the list of 45 non-HIV-related articles) that they felt contributed most to ID pharmacotherapy and to select the single most significant publication from the list of 17 articles related to HIV or AIDS. Of the 531 SIDP members surveyed, 100 responded (18.8%). The top 10 articles (9 non-HIV-related and 1 HIV-related) identified from this survey are summarized in this article. Three of the top 10 articles selected from the non-HIV category included new or updated ID guidelines. Summaries of the top articles selected (9 non-HIV-related and 1 HIV-related) from this survey are included. CONCLUSION: Due to the growing number of articles published each year, it is difficult to maintain a current knowledge of significant publications in ID. This review of significant publications in ID pharmacotherapy can be helpful by lessening this burden.

49th ICAAC annual meeting: optimization of anti-infective use in the clinical setting.

The meeting of the American Society of Microbiology was recently held in San Francisco, CA, USA - a gathering of experts in the fields of infectious diseases, microbiology and the pharmaceutical industry, among others. Owing to this large attendance and extensive coverage of many infectious disease topics, we focus on the optimization of anti-infective use in the clinical setting. We will cover antimicrobial stewardship, drugs with Gram-positive activity, and antifungal and antiretroviral agents.

Significant publications on infectious diseases pharmacotherapy in 2007.

PURPOSE: Significant publications on infectious diseases (ID) pharmacotherapy in 2007 were compiled and summarized. SUMMARY: On January 2, 2008, the 21 members of the Houston Infectious Disease Network (HIDN) were asked to select an article that was published in a peer-reviewed journal between January 1 and December 31, 2007, and write a summary highlighting why the article was significant to the diagnosis or treatment of ID. Articles were selected based on prior "top 10" presentations at major ID and pharmacy meetings or were listed as major articles in prominent ID journals. Priority was given to peer-reviewed publications and nationally recognized clinical treatment guidelines. Nineteen articles and summaries were submitted by HIDN members. The publication listing was distributed to Society of Infectious Diseases Pharmacists members via an Internet survey in early February 2008. Members were asked to select the 10 most significant articles relating to ID pharmacotherapy from the list of 19 and were allowed to add an additional article that was not already listed. A total of 102 individuals participated in the survey. A listing of the top 10 articles published in 2007 and one honorable mention was compiled, and the significance of each article was summarized. CONCLUSION: The increased number of articles in the peer-reviewed medical literature related to the diagnosis and treatment of ID has made it challenging to maintain a contemporary knowledge base of key publications. This summary of significant ID articles published in 2007 can help to alleviate the burden of knowledge management.

Impact of sample size on the performance of multiple-model pharmacokinetic simulations.

Monte Carlo simulations are increasingly used to predict pharmacokinetic variability of antimicrobials in a population. We investigated the sample size necessary to provide robust pharmacokinetic predictions. To obtain reasonably robust predictions, a nonparametric model derived from a sample population size of >/=50 appears to be necessary as the input information.

Full validation of an analytical method for the HIV-protease inhibitor atazanavir in combination with 8 other antiretroviral agents and its applicability to therapeutic drug monitoring.

Because HIV medications are used in combination, it is important to develop multiplex assays to streamline the therapeutic drug monitoring process and provide rapid turnaround. This article reports full validation of an analytical method that combines atazanavir with 6 HIV-protease inhibitors (indinavir, amprenavir, saquinavir, nelfinavir, ritonavir, and lopinavir) and 2 nonnucleoside reverse transcriptase inhibitors (nevirapine and efavirenz). Using 200 microL of plasma and a simple liquid-liquid extraction method, this analytical method achieved a clean baseline and high extraction efficiencies (90.0% to 99.5%). A Zorbax C-18 (150 x 4.6 mm, 3.5 microm) analytical column was used along with a 27-minute linear gradient elution of the mobile phase to provide sharp peaks at 210 nm. This method was validated over a range of 25 to 10,000 ng/mL and is accurate (90.4% to 110.5%) and precise (precision within a day and between days ranged from 2.3% to 8.3%). Because this method is simple and inexpensive, it may have applicability in countries with low resources.

Lopinavir/ritonavir induces the hepatic activity of cytochrome P450 enzymes CYP2C9, CYP2C19, and CYP1A2 but inhibits the hepatic and intestinal activity of CYP3A as measured by a phenotyping drug cocktail in healthy volunteers.

OBJECTIVE: The effect of lopinavir/ritonavir (LPV/r) administration on cytochrome P450 (CYP) enzyme activity was quantified using a phenotyping biomarker cocktail. Changes in CYP2C9, CYP2C19, CYP3A, CYP1A2, N-acetyltransferase-2 (NAT-2), and xanthine oxidase (XO) activities were evaluated using warfarin (WARF) + vitamin K, omeprazole (OMP), intravenous (IV) and oral (PO) midazolam (MDZ), and caffeine (CAF). DESIGN: : Open-label, multiple-dose, pharmacokinetic study in healthy volunteers. METHODS: Subjects (n = 14) simultaneously received PO WARF 10 mg, vitamin K 10 mg, OMP 40 mg, CAF 2 mg/kg, and IV MDZ 0.025 mg/kg on days (D) 1 and 14, and PO MDZ 5 mg on D2 and D15. LPV/r (400/100 mg twice daily) was administered on D4-17. CYP2C9 and CYP2C19 activities were quantified by S-WARF AUC0-inf and OMP/5-hydroxy OMP ratio, respectively. CYP1A2, NAT-2, and XO activities were quantified by urinary CAF metabolite ratios. Hepatic and intestinal + hepatic CYP3A activities were quantified by IV (CL) and PO (CL/F) MDZ clearance, respectively. RESULTS: After LPV/r therapy, CYP2C9, CYP2C19, and CYP1A2 activity increased by 29%, 100%, and 43% (P = 0.001, 0.046, and 0.001), respectively. No changes were seen in NAT-2 or XO activity. Hepatic and intestinal + hepatic CYP3A activity decreased by 77% (P < 0.001) and 92% (P = 0.001), respectively. CONCLUSION: LPV/r therapy results in modest induction of CYP1A2 and CYP2C9 and potent induction of CYP2C19 activity. Increasing doses of concomitant medications metabolized by these enzymes may be necessary. LPV/r inhibited intestinal CYP3A to a greater extent than hepatic CYP3A activity. Doses of concomitant CYP3A substrates should be reduced when combined with LPV/r, although intravenously administered compounds may require less of a relative dose reduction than orally administered compounds.