The Efficacy of a Didactic and Case-Based Pharmacogenomics Education Program on Improving the Knowledge and Confidence of Alberta Pharmacists.

Background: Pharmacogenomics (PGx) is the study of how genetic variations for functional proteins, such as metabolizing enzymes and drug receptors, impact drug pharmacokinetics and pharmacodynamics. In theory, pharmacists are well suited to utilize PGx in tailoring medications to patient genetics when providing medication therapy management services. However, PGx education needs to reach pharmacists prior to implementation. The aim of this study is to develop and evaluate a PGx course for pharmacists. Methods: A PGx education program was created and offered synchronously (virtual) and asynchronously (self-study) to pharmacists in Alberta, Canada. Lectures were delivered by experts live (virtual) with a question-and-answer period for synchronous sessions. These sessions were recorded for asynchronous delivery. Six case studies were discussed in large and small groups ("breakout rooms") in synchronous sessions, and provided for self-study in the asynchronous subgroup. Topics included genetic and PGx concepts; therapeutic applications; ethical, legal, and social considerations; and practical implementation. Pre- and post-course surveys measured self-rated knowledge using a 5-point Likert Scale and tested objective knowledge with a graded quiz. Results: Thirty-six pharmacists completed the course and both surveys. Participants reported backgrounds in community (88.9%) and hospital (38.9%) practice. Prior education in PGx was reported by 44.4% from degree programs and 27.8% from continuing education. Overall responses to statements about confidence in PGx moved from a median of "Disagree" at baseline to "Agree" after receiving PGx education (2-point difference [1,2] on 5-point Likert Scale; p < 0.001), indicating an increase in self-assessed competency in PGx. Likewise, mean participant grades on the knowledge quiz improved (20.8±21.9% pre-course vs 70.2±19.1% post-course, p < 0.001). There was no difference in these results between synchronous and asynchronous groups. Conclusion: A didactic and case-based PGx education program was effective at increasing pharmacist knowledge and confidence in PGx in both synchronous and asynchronous environments. Knowledge gained can be utilized in delivery of patient-centered, personalized medication therapy management in the pharmacy setting.

Applications for pharmacogenomics in pharmacy practice: A scoping review.

BACKGROUND: Pharmacogenomics (PGx) can provide valuable pharmacokinetic and pharmacodynamic information for the pharmacist's assessment of drug therapy, especially within medication therapy management (MTM) services. However, no review has comprehensively mapped the pharmacists' use of PGx in practice-based research. Doing so would allow future researchers, practitioners, and policy-makers to identify the ideal populations and settings for PGx implementation within the pharmacy. OBJECTIVE: The purpose of this review is to identify the evidence to date of PGx use in pharmacy practice. METHODS: A scoping review was conducted to find all studied non-oncologic pharmacy practices incorporating PGx testing. Search terms were applied to 5 databases and relevant journals. Characteristics of patients, pharmacy settings, genetic tests, and outcomes were summarized to determine models most likely to benefit patients. RESULTS: The search identified 43 studies on the use of PGx by pharmacists published between 2007 and 2020. CYP2C19 testing with antiplatelets was the most studied model, found in both community and institutional settings. It also was the most actionable test: approximately 30% of patients have polymorphisms indicating a need for alternative antiplatelets, and identifying these patients can reduce morbidity and mortality by more than 50%. As technology shifts, broader studies using multi-gene panel tests within MTM demonstrate an approximate 50% decrease in emergency visits and hospitalizations in elderly polypharmacy patients. Clinical benefit or drug-gene interactions are also found in other cardiovascular, psychiatric, analgesic, and gastrointestinal indications. No evaluations of actual costs or of pharmacist prescribing within pharmacy-based PGx have been performed. Facilitators towards successful PGx implementation included pharmacist education, collaboration with other healthcare providers, and the use of clinical decision software. CONCLUSIONS: Pharmacogenomic testing has demonstrated feasibility and improved medication outcomes in pharmacy practice, including in the community pharmacy. Further PGx research should be directed towards pharmacist prescribing, pharmacist education, and pharmacoeconomics.

Bayesian estimation of pharmacokinetic parameters: an important component to include in the teaching of clinical pharmacokinetics and therapeutic drug monitoring.

Bayesian estimation of pharmacokinetic parameters (PKP), as discussed in this review, provides a powerful approach towards the individualization of dosing regimens. The method was first described by Lewis Sheiner and colleagues and it is well suited in clinical environs where few blood fluid measures of drugs are available in the clinic. This makes it a valuable tool in the effective implementation of therapeutic drug monitoring. The principle behind the method is Bayes theorem, which incorporates elements of variability in a priori-known population estimates and variability in the pharmacokinetic parameters, and known errors intrinsic to the assay method used to estimate the blood fluid drug concentrations. This manuscript reviews the Bayesian method. The literature was scanned using Pubmed to provide background into the Bayesian method. An Add-in for Excel program was used to show the ability of the method to estimate PKP using sparse blood fluid concentration vs time data. Using a computer program, the method was able to find reasonable estimates of individual pharmacokinetic parameters, assessed by comparing the estimated data to the true PKP. Education of students in clinical pharmacokinetics is incomplete without some mention and instruction of the Bayesian forecasting method. For a complete understanding, a computer program is needed to demonstrate its utility.

Pharmacokinetic interaction between linagliptin and tadalafil in healthy Egyptian males using a novel LC-MS method.

Aim: Assessment of pharmacokinetic interaction between linagliptin (LNG) and tadalafil (TDL) in healthy males. Methods: First, a novel LC-MS method was developed; second, a Phase IV, open-label, cross-over study was performed. Volunteers took single 20-mg TDL dose on day 1 followed by wash out period of 2 weeks then multiple oral dosing of 5-mg/day LNG for 13 days. On day 13, volunteers were co-administered 20-mg TDL. Results: LNG and TDL single doses did not affect QTc interval. Smoking did not alter pharmacokinetics/pharmacodynamics of LNG and TDL. Co-administration of LNG with TDL resulted in TDL longer time to reach maximum plasma concentration (Tmax), decreased oral clearance (Cl/F) and oral volume of distribution (Vd/F), increased its maximum plasma concentration (Cmax), area under concentration-time curve (AUC), muscle pain and QTc prolongation. Conclusion: LNG and TDL co-administration warrants monitoring and/or TDL dose adjustment.

Novel cremochylomicrons for improved oral bioavailability of the antineoplastic phytomedicine berberine chloride: Optimization and pharmacokinetics.

Berberine chloride (BER) is an antineoplastic phytomedicine that combat non-Hodgkin lymphoma. BER suffers from low oral bioavailability due to p-glycoprotein efflux and first-pass metabolism. Lymphatic drug targeting recently gained a profound attention due to circumventing hepatic first-pass metabolism and targeting lymph diseases. Therefore, novel BER-loaded cremochylomicrons were elaborated to mitigate BER drawbacks and enhance its lymphatic targeting and bioavailability. Optimized cremochylomicron was prepared with 2.5%w/v Cremophor El and 12.5% w/w berberine content. Promising in vitro characteristics (particle size = 175.6 nm and entrapment efficiency = 95.5%) were obtained. Lyophilized system showed high colloidal stability over 6 months. In addition in vivo pharmacokinetics study demonstrated significant enhancement (>2fold) in the rate and extent of absorption in cremochylomicron over free BER. Moreover, cremochylomicrons demonstrated in significant increase in mean residence time and volume of distribution with decreased intestinal drug clearance as a result of efflux inhibition. In another avenue, a significant reduction in BER absorption (43%) in presence of cycloheximide inhibitor was obtained confirming the lymphatic targeting ability of cremochylomicrons. In conclusion, berberine-loaded cremochylomicron could be considered as a promising nanoplatform for targeting lymphatic system and improving BER oral bioavailability with lower dose and side effects.

Hyperlipidemia Alters the Pharmacokinetics of Posaconazole and Vincristine Upon Co-Administration in Rats.

OBJECTIVES: Co-administration of posaconazole (PSZ) and vincristine (VCR) in the treatment of patients with acute lymphoblastic leukemia increases the neurotoxicity of VCR. Our aim is to study the effect of increased lipoprotein levels on the pharmacokinetics of PSZ and VCR upon co-administration in rats. METHODS: Rats were assigned to three groups, normolipidemic (NL), intermediate hyperlipidemic (IHL), and extreme hyperlipidemic (HL) groups. All rats were administered PSZ orally followed by VCR intravenously 4 h later. For the pharmacokinetic study, serial plasma samples were collected over 96 h and for tissue distribution study; plasma, lung, and liver tissues were collected over 48 h post oral dosing. RESULTS: Posaconazole showed higher plasma concentrations than VCR at all time points. Co-administration of VCR with PSZ reduced PSZ weight normalized oral clearance, increased PSZ area under the plasma concentration-time curve (AUC) from time zero to infinity, showed higher PSZ liver concentrations, and increased VCR volume of distribution of the central compartment. Upon increasing the lipoprotein levels, PSZ showed higher plasma availability and delayed tissue distribution, whereas VCR had shown a significant decrease in PSZ AUC0-24h, AUC0-tlast, and AUCo-inf (NL = IHL > HL) and a significant increase in the volume of distribution (NL = IHL < HL). Vincristine has shown higher tissue uptake and concentrations. CONCLUSION: Monitoring cholesterol and triglyceride levels in patients with acute lymphoblastic leukemia is advisable to decrease VCR neurological side effect incidences and delay the activity of both PSZ and VCR.

Studying the knowledge, attitude and practice of antibiotic misuse among Alexandria population.

AIM: To assess knowledge, attitude and practice (KAP) of antimicrobial self-medication among a convenience sample of population in Alexandria, Egypt. METHODOLOGY: A descriptive cross-sectional study using a self-administrated semi-constructed questionnaire. A convenience sample of 359 participants was studied using appropriate consent. The questionnaire had four sections: demographics, KAP, professional medical knowledge and attitude of children caregivers toward antimicrobial self-medication. The questionnaire was initially constructed in English and then translated into its final Arabic version. The Arabic version was pilot-tested and face-validated. Descriptive and quantitative analysis were performed using SPSS (V.20.0). RESULTS: Approximately 64% (231) of the studied population used antibiotics without prescription in the past 12 months. This was significantly correlated with female gender and lack of knowledge. The main reason for self-medication was due to saving time and effort (109, 47%) followed by not preferring doctor visits (89, 39%). More than 60% of cases used amoxicillin-clavulanic acid. The main sources of antibiotics were leftovers from previously prescribed pharmaceuticals and those purchased from community pharmacies. 85 participants were young children caregivers of which 18 (21%) reported administering antibiotics to their children without consulting a physician. Out of 115 who claimed attaining medical background, only 30 (26%) managed to answer section 3 correctly with 23 of them reporting antibiotic self-medication. CONCLUSION: This study showed an increased tendency towards antibiotic self-medication among Alexandrian adults and children that was not significantly decreased in population with medical background. The reasons discussed within the study should be further addressed to decrease such practice.

The effect of increased lipoproteins levels on the disposition of vincristine in rat.

BACKGROUND: Vincristine (VCR), an antineoplastic agent, is a key component in the treatment of acute lymphoblastic leukemia, lymphomas, rhabdomyosarcoma, neuroblastoma, and Wilms' tumor diseases. Recently, high incidence of hyperlipidemia was reported to be associated with allogenic hematopoietic stem cell transplantation and VCR/L-asparaginase therapy. The aim of this study is to test the effects of incremental increase in lipoproteins levels on vincristine disposition in rat. METHOD: To study VCR pharmacokinetics and protein binding, rats (n = 25) were assigned to three groups, normal lipidemic (NL), intermediate (IHL) and extreme hyperlipidemic (HL). Hyperlipidemia was induced by ip injection of (1 g/Kg) poloxamer 407 in rats. Serial blood samples were collected using the pre-inserted jugular vein cannula for 72 h post VCR (0.15 mg/Kg) i.v. dose. VCR unbound fractions in NL, IHL and HL plasma were determined using ultrafiltration kits. RESULTS: VCR demonstrated a rapid distribution phase (6-8 h) followed by a slower elimination phase with a mean elimination t½ of ~ 14 h. VCR exhibited moderate binding to plasma proteins ~ 83 %. It showed a relatively small Vc (~0.17 L/Kg) and a larger Vß (1.53 L/Kg) indicating good tissue distribution. As the lipoproteins levels were increased, no significant changes were noted in VCR unbound fraction, plasma concentration, or volume of distribution indicating low affinity to lipoprotein binding. Induced HL also did not affect VCR elimination where similar VCR AUC0-∞, Cl and elimination phase t½ were reported along the different lipemic groups. CONCLUSION: Incremental increase in lipoprotein levels resulted in no significant effect on VCR disposition as such ALL malignant lymphoma and allogenic hematopoietic stem cell transplantation patients need not to worry about HL-VCR interaction. Whether, HL can potentiate another drug-drug or drug-disease interaction involving VCR warrants further studying and monitoring to ensure therapeutic safety and efficiency.

Stability-Indicating HPLC-DAD Method for the Determination of Linagliptin in Tablet Dosage Form: Application to Degradation Kinetics.

This work aims to develop HPLC-DAD method for linagliptin (LNG) quantitation in the presence of its degradation products in tablets and to study its degradation kinetics. LNG samples were extracted from tablets and diluted. Various ICH degradation conditions were applied to study LNG degradation kinetics. LNG was assayed by a C18 column using a simple isocratic mobile phase (methanol:water containing 0.3% TEA, 40:60, pH 4.5) pumped at 1 mL/min. The drug was detected at 225 nm. The method showed high linearity (r2 > 0.999) with CV% and % error of the mean <2% over the range of 1-50 µg/mL. Limits of detection and quantitation were 0.3 and 1.0 µg/mL, respectively. LNG retention time was 11 min with a total run time of 17 min. In all degradation conditions applied, LNG was well separated from its degradation products. The method was successfully used to quantitate LNG content in its tablets and study its degradation kinetics in acidic, alkaline and oxidative forced degradation experiments. In conclusion, simple, precise and reliable method for the separation and determination of LNG in the presence of its degradation products under different stress conditions was developed and validated according to the latest ICH guidelines.

The effect of hyperlipidemia on the pharmacokinetics, hepatic and pulmonary uptake of posaconazole in rat.

OBJECTIVES: Posaconazole (PSZ), lipophilic antifungal drug, is used for prophylactic purposes in immunocompromised patients. Our aim is to study its pharmacokinetics and tissue distribution in different elevated lipoprotein levels in rat. METHODS: To study PSZ pharmacokinetics and protein binding, rats (n=30) were assigned to three groups, normal lipidemic (NL), intermediate (IHL) and extreme hyperlipidemic (HL). Hyperlipidemia was induced by i.p. injection of (1g/kg) poloxamer 407 in rats. Serial blood samples were collected for 72h p.o. PSZ (40mg/kg). PSZ unbound fractions in NL, IHL and HL plasma were determined using ultrafiltration kits. To study tissue distribution, rats (n=64) were allocated into NL and HL groups. After p.o. administration of PSZ 40mg/kg, blood samples were collected, lungs and liver tissues were extracted over 72h. RESULTS: Orally dosed rats showed two distinct Cmax peaks reflecting PSZ enterohepatic circulation. The incremental increase in lipoprotein levels have resulted in significant decrease in PSZ unbound fraction, a significant increase in Cmax1 and the AUC0-24h (NL=IHL

HPLC Methods for Quantitation of Exemestane-Luteolin and Exemestane-Resveratrol Mixtures in Nanoformulations.

Two HPLC-DAD assays for the simultaneous quantitation of exemestane (EXE) and resveratrol (RES)-Mix 1-and EXE and luteolin (LUT)-Mix 2-in novel breast cancer therapy nanoformulations were developed. Calibration curves 15-30 µg/mL and samples were injected through an Inertsil ODS-3 (250 × 4.6 mm, 5 µm) column. The gradient elution for Mix 1 was methanol : 0.05% (v/v) acetic acid in water (60 : 40 to 80 : 20, linear over 2 min), and for Mix 2, it was methanol : water (60 : 40 for 4 min, then ramped linearly to 90 : 10, over 12 min) pumped at 1.5 mL/min for 4 min, then 1 mL/min till the end of run. EXE, RES, LUT and flutamide (internal standard (IS)) were measured at 246, 307, 350 and 300 nm, respectively. For Mix 1, RES, EXE and IS eluted at 3.5, 6.8 and 7.4 min, respectively, while for Mix 2, LUT, EXE and IS eluted at 7.5, 11.4 and 12.7 min, respectively. The mean r(2) for the standard curves was ≥0.99, and percentage coefficient of variation and % error of the mean were <2. Both assays successfully quantitated Mix 1 and Mix 2 in their nanoformulations. The two developed assays were sensitive and selective for the analysis of EXE-LUT and EXE-RES mixtures in nanoformulations according to International Conference on Harmonization guidelines.

Ketoconazole Stereoisomers Differentially Induce Cytochrome P450 1A1 Between Human Hepatoma HepG2 and Mouse Hepatoma Hepa1c1c7 Cells.

Ketoconazole (KTZ) has 2 chiral centers with the therapeutically active form being a racemic mixture of 2 cis-enantiomers, namely, (2R,4S)-(+)-KTZ and (2S,4R)-(-)-KTZ. The aims of the present study were to examine the effects of (+)-KTZ, (-)-KTZ, and (±)-KTZ on aryl hydrocarbon receptor activation and subsequently CYP1A1 induction in both human HepG2 and murine Hepa1c1c7 hepatoma cells, and to further test their inhibitory effect using recombinant human and mouse CYP1A1 enzymes. Our results demonstrated that (+)-KTZ induced human CYP1A1 more than (-)-KTZ, whereas on the other hand (-)-KTZ induced murine Cyp1a1 more than (+)-KTZ at the mRNA, and activity levels. Human CYP1A1 showed higher affinity to 7ER compared with murine Cyp1a1 (Km values 13.29 nM for human vs. 168.1 nM for murine). The intrinsic clearance values for human and murine CYP1A1 were 194.1 and 87.6 µL/pmol P450/min, respectively, whereas, Vmax values were 2.58 and 14.73 pmol/pmol P450/min, respectively. (+)-KTZ and (-)-KTZ directly inhibited CYP1A1 activity by noncompetitive mechanism. The affinity of (-)-KTZ to interact with human CYP1A1 and murine Cyp1a1 was significantly different from (+)-KTZ, as the Ki values for human CYP1A1 and murine Cyp1a1 were 199.4 and 413.7 nM, respectively, for (+)-KTZ, and 269.3 and 230.8 nM, respectively, for (-)-KTZ.

HPTLC Determination of Three Gliptins in Binary Mixtures with Metformin.

A single, simple, selective and validated high performance thin layer chromatographic (HPTLC) method was developed for the determination of either linagliptin (LGP), saxagliptin (SGP) or vildagliptin (VGP) in their binary mixtures with metformin (MET) in pharmaceutical preparations using environmentally preferable green mobile phase system. Separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 using methanol-0.5% w/v aqueous ammonium sulfate (8 : 2, v/v) as mobile phase. Densitometric measurement of the spots was performed at 225 nm for LGP/MET mixture and at 208 nm for both SGP/MET and VGP/MET mixtures. The linear regression analysis data were used for the regression line in the range of 0.05-0.5 µg/band for LGP and SGP and 0.2-2 and 5-40 µg/band for VGP and MET, respectively. The method was validated and showed good performances in terms of linearity, limits of detection and quantitation, precision, accuracy, selectivity and specificity. The calculated percentage relative error values and percentage relative standard deviation for intra- and interday precision studies did not exceed 2%. The developed method was satisfactorily applied for the analysis of pharmaceutical preparations and proved to be specific and accurate for the quality control of the cited drugs in their dosage forms.

High Performance Liquid Chromatographic Assay for the Simultaneous Determination of Posaconazole and Vincristine in Rat Plasma.

Purpose. Developing a validated HPLC-DAD method for simultaneous determination of posaconazole (PSZ) and vincristine (VCR) in rat plasma. Methods. PSZ, VCR, and itraconazole (ITZ) were extracted from 200 µL plasma using diethyl ether in the presence of 0.1 M sodium hydroxide solution. The organic layer was evaporated in vacuo and dried residue was reconstituted and injected through HC-C18 (4.6 × 250 mm, 5 µm) column. In the mobile phase, acetonitrile and 0.015 M potassium dihydrogen orthophosphate (30 : 70 to 80 : 20, linear gradient over 7 minutes) pumped at 1.5 mL/min. VCR and PSZ were measured at 220 and 262 nm, respectively. Two Sprague Dawley rats were orally dosed PSZ followed by iv dosing of VCR and serial blood sampling was performed. Results. VCR, PSZ, and ITZ were successfully separated within 11 min. Calibration curves were linear over the range of 50-5000 ng/mL for both drugs. The CV% and % error of the mean were ≤18% and limit of quantitation was 50 ng/mL for both drugs. Rat plasma concentrations of PSZ and VCR were simultaneously measured up to 72 h and their calculated pharmacokinetics parameters were comparable to the literature. Conclusion. The assay was validated as per ICH guidelines and is appropriate for pharmacokinetics drug-drug interaction studies.

A Comparative Study of Newly Developed HPLC-DAD and UHPLC-UV Assays for the Determination of Posaconazole in Bulk Powder and Suspension Dosage Form.

Objective. To develop and compare HPLC-DAD and UHPLC-UV assays for the quantitation of posaconazole in bulk powder and suspension dosage form. Methods. Posaconazole linearity range was 5-50 µg/mL for both assays. For HPLC-DAD assay, samples were injected through Zorbax SB-C18 (4.6 × 250 mm, 5 µm) column. The gradient elution composed of the mobile phase acetonitrile: 15 mM potassium dihydrogen orthophosphate (30 : 70 to 80 : 20, linear over 7 minutes) pumped at 1.5 mL/min. For UHPLC-UV assay, samples were injected through Kinetex-C18 (2.1 × 50 mm, 1.3 µm) column. The mobile phase composed of acetonitrile: 15 mM potassium dihydrogen orthophosphate (45 : 55) pumped isocratically at 0.4 mL/min. Detection wavelength was 262 nm in both methods. Results. The run time was 11 and 3 minutes for HPLC-DAD and UHPLC-UV assays, respectively. Both assays were linear (r (2) > 0.999) with CV% and % error of the mean <3%. Limits of detection and quantitation were 0.82 and 2.73 µg/mL for HPLC-DAD and 1.04 and 3.16 µg/mL for UHPLC-UV, respectively. The methods quantitated PSZ in suspension dosage form with no observable interferences. Conclusions. Both assays were proven sensitive and selective according to ICH guidelines. UHPLC-UV assay exhibited some economic and chromatographic separation superiority.

Effect of rat serum lipoproteins on mRNA levels and amiodarone metabolism by cultured primary rat hepatocytes.

Hyperlipidemia can significantly increase amiodarone (AM) in vivo liver uptake and decrease its velocity of microsomal metabolism. Here, hepatocytes isolated from normolipidemic (NL) and hyperlipidemic rats were incubated with AM in the presence or absence of diluted NL or hyperlipidemic serum. The serum was added either as preincubation before drug, or concurrently with drug; incubations without rat serum were used as controls. The hepatocyte levels of mRNA for several proteins and enzymes were also measured. Disappearance of AM was seen up to 72 h. There was little difference between hepatocytes from NL or hyperlipidemic animals in intrinsic clearance (CL(int) ) of AM. The effect of hyperlipidemic rat serum, either before or with AM, was profound, causing a significant reduction in the CL(int) . Reductions were seen in mRNA for cytochrome P450 1A1, 3A2, and 2D1, some transporters, and low-density lipoprotein receptors after exposure of hepatocytes to lipoprotein-rich sera. In conclusion, exposure of isolated hepatocytes to hyperlipidemic serum caused decreases in AM CL(int) and lower mRNA levels for some proteins involved in the uptake and metabolism of AM. When coincubated with serum, an additional effect of increased binding to lipoproteins seemed to further contribute to a reduced CL of AM.

Posaconazole-vincristine coadministration triggers seizure in a young female adult: a case report.

Coadministration of azoles and vincristine has been shown to increase vincristine neurotoxic effects due to the inhibition of cytochrome P450 (CYP) isoform 3A4, for which vincristine is a substrate. Despite the absence of any casual relationship between seizure and coadministration of azoles, few case reports of vincristine-induced seizure have been documented after coadministration of fluconazole or posaconazole in children. In this paper we are reporting the first young female adult who experienced generalized seizure after coadministration of posaconazole and vincristine. The 19-year-old female was diagnosed with acute lymphoblastic leukemia. She started induction phase of Berlin Frankfurt Muenster protocol along with posaconazole 200 mg three times daily as prophylactic antifungal therapy. Five days after the third vincristine dose, she developed generalized seizure accompanied by high blood pressure and SIADH. Her neurological exam/CT scan did not show any abnormality. In conclusion, this study reports a novel finding in the sense that all previous case reports pertaining to posaconazole-vincristine-induced seizure in literature involved children. Physicians should be made aware of this rare possible outcome to closely monitor their patients and take appropriate measures to prevent such possible adverse effect.

Effect of serum lipoproteins on stereoselective halofantrine metabolism by rat hepatocytes.

Experimental hyperlipidemia has shown to decrease cytochrome P450 3A4 and 2C11 expression and to increase liver concentrations and the plasma protein binding of halofantrine (HF) enantiomers. The present study examined the effect of hyperlipidemic (HL) serum on the metabolism of HF enantiomers by primary rat hepatocytes. Hepatocytes from normolipidemic (NL) and HL (poloxamer 407 treated) rats were incubated with rac-HF in cell media with or without additional rat serum (5%). In those incubations with rat serum, the hepatocytes were preincubated or coincubated with serum from NL or HL rats. Rat serum-free hepatocyte incubations served as controls. Stereospecific assays were used to measure HF and desbutylhalofantrine (its major metabolite) enantiomer concentrations in whole well contents (cells + media). Concentrations of desbutylhalofantrine were not measurable. The disappearance (apparent metabolism) of (-)-HF exceeded that of antipode, but HF metabolism did not differ between hepatocytes from NL and HL rats. Coincubation of HL rat serum with NL hepatocytes caused a significant decrease in the disappearance of (-)-HF, whereas in HL hepatocytes, a substantially decreased apparent metabolism was noted for both enantiomers. Compared with NL serum, (-)-HF disappearance was significantly lowered upon preincubation of NL hepatocytes with HL serum. A combination of factors including diminished drug metabolizing or lipoprotein receptor expression, and increased plasma protein binding in the wells, may have contributed to a decrease in apparent metabolism of the HF enantiomers in the presence of lipoproteins from HL rat serum.

Effect of hyperlipidemia on ketoconazole-midazolam drug-drug interaction in rat.

Hyperlipidemia (HL) was previously shown to lower liver uptake of the more potent (-) enantiomer of ketoconazole (KTZ) in rat. The current study examined the possible modifying influence of experimental HL on a KTZ pharmacokinetic interaction with midazolam (MDZ). Normolipidemic and hyperlipidemic rats were administered a single intravenous dose of MDZ (5 mg/kg) with or without a single oral dose of racemic KTZ (40 mg/kg). Serial blood samples were collected over 8 h following MDZ injections via jugular vein cannulas. Plasma was jointly assayed for MDZ and KTZ concentrations using a validated assay. MDZ mean clearance (CL) was unchanged by KTZ coadministration. HL caused a significantly 61% lower MDZ-unbound fraction and decreases in volume of distribution (VD) but by itself had no effect on MDZ CL. This suggested that MDZ could bind to lipoproteins. With KTZ coadministered to hyperlipidemic rats, there were significant decreases in MDZ CL and VD. HL caused a decrease in unbound plasma fraction of oral KTZ but no significant difference in its pharmacokinetics. HL caused a more pronounced KTZ-associated inhibition of MDZ CL. This may be related to the decrease of MDZ's unbound fraction and perhaps to attenuation of CYP3A by HL in the rat.

The effect of increased lipoprotein levels on the pharmacokinetics of ketoconazole enantiomers in the rat.

(±)-Ketoconazole (KTZ) is a chiral antifungal drug that inhibits cytochrome P450 (CYP)-mediated metabolism of other drugs. Because of its lipophilicity, KTZ pharmacokinetics might change in elevated plasma lipoprotein concentrations. To explore that, the stereoselective pharmacokinetics of KTZ were assessed in a rodent model of hyperlipidaemia (HL). Rats were given KTZ intravenously (i.v.) or orally. Serial blood samples were collected over 24 h for the iv dosed groups. After oral doses, plasma and liver specimens were obtained up to 6 h after dosing. All specimens were assayed using stereospecific assay. Orally and iv dosed rats showed no significant differences between normolipidemic and hyperlipidaemic area under the plasma concentrations vs. time curves or clearance (CL), of both KTZ enantiomers. In iv dosed rats, however, the volume of distribution (V(ss)) was significantly higher in HL for both enantiomers. The (+):(-) KTZ ratios of CL and V(ss) were also higher in hyperlipidaemic rats. After oral doses, the liver to plasma concentration ratios of (-)-KTZ (but not antipode) were significantly lower in HL. In conclusion, HL caused an increase in V(ss), and possibly decreased liver uptake of the more potent CYP-inhibiting (-) enantiomer.