Time course of CYP3A activity during and after metamizole (dipyrone) in healthy volunteers.

AIMS: In patients of all ages, metamizole is a frequently used analgesic. Recently, metamizole has been identified as an inducer of, among others, cytochrome P450 (CYP) 3A activity, but the time course of this interaction has not been evaluated. METHODS: Using repeated oral microdoses (30 µg) of the CYP3A index substrate midazolam, we assessed changes in midazolam pharmacokinetics (area under the concentration-time curve from 2-4 h: AUC2-4 and estimated partial metabolic clearance: eClmet ) before, at steady-state, and after discontinuation of 3 × 1000 mg metamizole/day orally for 8 days. RESULTS: Significant changes in pharmacokinetic parameters were detected already 3 days after start of metamizole treatment. At the steady-state of enzyme induction, the geometric mean ratio of midazolam AUC2-4 was substantially reduced to 0.18 (90% confidence interval: 0.14-0.24) with a corresponding 5.43-fold (4.15-7.10) increase of eClmet . After discontinuation of metamizole, the changes slowly recovered, but were still significant at the end of the observation period on the fifth day after discontinuation of metamizole therapy (AUC2-4 reduced to 0.50 [0.41-0.63] and eClmet 1.99-fold increased [1.60-2.47, P < 0.05]). CONCLUSION: Metamizole acts as a strong inducer of CYP3A already few days after start of metamizole administration and, thus, should be avoided in patients using drugs with narrow therapeutic index and major clearance via CYP3A. If their administration is essential, close monitoring and dose adjustment of comedication should be performed as early as the first week after the initiation and after discontinuation of metamizole therapy.

Effect of Clarithromycin, a Strong CYP3A and P-glycoprotein Inhibitor, on the Pharmacokinetics of Edoxaban in Healthy Volunteers and the Evaluation of the Drug Interaction with Other Oral Factor Xa Inhibitors by a Microdose Cocktail Approach.

PURPOSE: We assessed the differential effect of clarithromycin, a strong inhibitor of cytochrome P450 (CYP) 3A4 and P-glycoprotein, on the pharmacokinetics of a regular dose of edoxaban and on a microdose cocktail of factor Xa inhibitors (FXaI). Concurrently, CYP3A activity was determined with a midazolam microdose. METHODS: In an open-label fixed-sequence trial in 12 healthy volunteers, the pharmacokinetics of a microdosed FXaI cocktail (µ-FXaI; 25 µg apixaban, 50 µg edoxaban, and 25 µg rivaroxaban) and of 60 mg edoxaban before and during clarithromycin (2 x 500 mg/d) dosed to steady-state was evaluated. Plasma concentrations of study drugs were quantified using validated ultra-performance liquid chromatography-tandem mass spectrometry methods. RESULTS: Therapeutic clarithromycin doses increased the exposure of a therapeutic 60 mg dose of edoxaban with a geometric mean ratio (GMR) of the area under the plasma concentration-time curve (AUC) of 1.53 (90 % CI: 1.37-1.70; p < 0.0001). Clarithromycin also increased the GMR (90% CI) of the exposure of microdosed FXaI apixaban to 1.38 (1.26-1.51), edoxaban to 2.03 (1.84-2.24), and rivaroxaban to 1.44 (1.27-1.63). AUC changes observed for the therapeutic edoxaban dose were significantly smaller than those observed with the microdose (p < 0.001). CONCLUSION: Clarithromycin increases FXaI exposure. However, the magnitude of this drug interaction is not expected to be clinically relevant. The edoxaban microdose overestimates the extent of the drug interaction with the therapeutic dose, whereas AUC ratios for apixaban and rivaroxaban were comparable to the interaction with therapeutic doses as reported in the literature. TRIAL REGISTRATION: EudraCT Number: 2018-002490-22.

Oral bioavailability of microdoses and therapeutic doses of midazolam as a 2-dimensionally printed orodispersible film in healthy volunteers.

PURPOSE: The use of two-dimensional (2D) printing technologies of drugs on orodispersible films (ODF) can promote dose individualization and facilitate drug delivery in vulnerable patients, including children. We investigated midazolam pharmacokinetics after the administration of 2D-printed ODF. METHODS: Midazolam doses of 0.03 and 3 mg were printed on an ODF using a 2D drug printer. We investigated the bioavailability of the two midazolam doses with ODF swallowed immediately (ODF-IS) or delayed after 2 min (ODF-DS) by comparing their pharmacokinetics with intravenous and oral midazolam solution in 12 healthy volunteers. RESULTS: The relative bioavailability of ODF-IS 0.03 mg was 102% (90% confidence interval: 89.4-116) compared to oral solution and for 3 mg 101% (86.8-116). Cmax of ODF-IS 0.03 mg was 95.5% (83.2-110) compared to oral solution and 94.3% (78.2-114) after 3 mg. Absolute bioavailability of ODF-IS 0.03 mg was 24.9% (21.2-29.2) and for 3 mg 28.1% (23.4-33.8) (oral solution: 0.03 mg: 24.4% (22.0-27.1); 3 mg: 28.0% (25.0-31.2)). Absolute bioavailability of ODF-DS was significantly larger than for ODF-IS (0.03 mg: 61.4%; 3 mg: 44.1%; both p < 0.0001). CONCLUSION: This trial demonstrates the tolerability and unchanged bioavailability of midazolam printed on ODF over a 100-fold dose range, proving the suitability of ODF for dose individualization. Midazolam ODF-IS AUC0-∞ in both doses was bioequivalent to the administration of an oral solution. However, Cmax of the therapeutic dose of ODF-IS missed bioequivalence by a clinically not relevant extent. Prolonged mucosal exposure increased bioavailability. (Trial Registration EudraCT: 2020-003984-24, August 10, 2020).

Minor contribution of cytochrome P450 3A activity on fentanyl exposure in palliative care cancer patients.

Transdermal fentanyl is widely used to control pain in cancer patients. The high pharmacokinetic variability of fentanyl is assumed to be due to cytochrome P450 3A-mediated (CYP3A) N-dealkylation to norfentanyl in humans. However, recently published clinical studies question the importance of the described metabolic pathway. In this small study in palliative cancer patients under real-life clinical conditions, the influence of CYP3A on fentanyl variability was investigated. In addition to the determination of midazolam plasma concentration to reveal CYP3A activity, plasma concentrations of fentanyl and its metabolite, norfentanyl, were measured in identical blood samples of 20 patients who participated in an ongoing trial and had been on transdermal fentanyl. Fentanyl, norfentanyl, midazolam, and 1'-OH-midazolam were quantified by liquid chromatography/tandem mass spectrometry. Plasma concentrations of fentanyl and norfentanyl exhibited a large variability. Mean estimated total clearance of fentanyl and mean metabolic clearance of midazolam (as a marker of CYP3A activity) were 75.5 and 36.3 L/h. Both clearances showed a weak correlation and hence a minimal influence of CYP3A on fentanyl elimination.

Alteration of drug-metabolizing enzyme activity in palliative care patients: Microdosed assessment of cytochrome P450 3A.

BACKGROUND: Cytochrome P450 3A is the most relevant drug-metabolizing enzyme in humans as it is involved in the elimination of 50% of marketed drugs. Nothing is known about the activity of cytochrome P450 3A in palliative care patients who have complicated symptoms often associated with a terminal illness. AIM: In order to improve drug dosing in end-of-life care and to avoid drug interactions, cytochrome P450 3A activity was determined in patients of a palliative care unit under real-life clinical conditions. DESIGN: As midazolam is an established marker substance for cytochrome P450 3A activity, this single-arm prospective trial was designed to obtain a 4-h pharmacokinetic profile of midazolam after oral administration of a 10-µg dose from each enrolled patient. Plasma concentrations of midazolam and its primary metabolite 1'-hydroxy-midazolam were quantified by mass spectrometry techniques. Cytochrome P450 3A activity was calculated as partial metabolic clearance from a limited sampling area under the curve. All other drugs taken by the participating patients were considered, as well as recent blood test results and patients' diagnoses. The trial was registered at German Clinical Trials Register ( www.drks.de ): DRKS00011753. SETTING/PARTICIPANTS: The trial was carried out at a university palliative care unit under real-life clinical conditions. Every patient admitted to the ward was screened for possible participation, independent of the individual performance status. RESULTS: Partial metabolic clearance of midazolam in palliative care patients was 31.7 ± 32.1 L/h. This was a highly significant 40% reduction (p < 0.0001) in comparison with the cytochrome P450 3A activity of healthy subjects. CONCLUSION: Dosing of cytochrome P450 3A substrate drugs (e.g. macrolide antibiotics, benzodiazepines, calcium channel blockers) needs to be adjusted in palliative care patients; otherwise, escalation of debilitating symptoms due to drug interactions might occur.

Decreased Cytochrome P450 3A activity in palliative patients with haematological diseases: Potential impact on supportive drug therapies.

Cytochrome P450 3A (CYP3A) is the most relevant drug-metabolizing enzyme in human beings involved in the elimination of about 50% of the marketed drugs. Comprehensive in vivo data of CYP3A activity in palliative patients with haematological diseases are missing. Therefore, CYP3A activity was determined under real-life clinical conditions in patients to gain knowledge about dose adjustments for supportive therapies and symptom management in haematology. The single-arm, prospective trial obtained a 4-hours pharmacokinetic profile of midazolam after oral administration of a microdose as marker substance from each enrolled patient. Plasma concentrations of midazolam and its primary metabolite 1'-hydroxy-midazolam were quantified by mass spectrometry techniques. CYP3A activity was calculated as partial metabolic clearance from an established limited sampling area under the curve. All other drugs taken by the participating patients were considered as well as recent laboratory test results and the patients' diagnoses. Partial metabolic clearance of midazolam in patients with haematological diseases was highly variable (36.9 ± 52.7 L/h). In comparison with the CYP3A activity of healthy individuals, this was a highly significant 30% reduction of activity (P < 0.0001). Dosing of major CYP3A substrate drugs needs to be reduced in palliative patients with haematological diseases, otherwise escalation of debilitating symptoms due to drug interactions might occur.

Neuropsychiatric manifestations among HIV-1 infected African patients receiving efavirenz-based cART with or without tuberculosis treatment containing rifampicin.

PURPOSE: Efavirenz-based combination antiretroviral therapy (cART) is associated with neuropsychiatric adverse events. We investigated the time to onset, duration, clinical implications, impact of pharmacogenetic variations, and anti-tuberculosis co-treatment on efavirenz-associated neuropsychiatric manifestations. METHODS: Prospective cohort study of cART naïve HIV patients with or without tuberculosis (HIV-TB) co-infection treated with efavirenz-based cART. Rifampicin-based anti-tuberculosis therapy was initiated 4 weeks prior to efavirenz-based cART in HIV-TB patients. Data on demographic, clinical, laboratory, and a 29-item questionnaire on neuropsychiatric manifestations were collected for 16 weeks after cART initiation. Genotyping for CYP2B6, CYP3A5, SLCO1B1, and ABCB1 and quantification of efavirenz plasma concentration were done on the 4th and 16th week. RESULTS: Data from 458 patients (243 HIV-only and 215 HIV-TB) were analyzed. Overall incidence of neuropsychiatric manifestations was 57.6% being higher in HIV-only (66.7%) compared to HIV-TB patients (47.4%) (p < 0.01). HIV-only patients were more symptomatic, with proportionately higher grades of manifestations compared to HIV-TB patients. Median time to manifestations was 1 week after cART initiation in HIV-only and 6 weeks after anti-TB (i.e., 2 weeks after cART initiation) in HIV-TB patients. HIV-only patients had significantly higher efavirenz plasma concentrations at 4 weeks after cART compared to HIV-TB patients. No association of sex or genotype was seen in relation to neuropsychiatric manifestations. Risk for neuropsychiatric manifestations was three times more in HIV-only patients compared to HIV-TB (p < 0.01). CONCLUSIONS: Incidence of neuropsychiatric manifestations during early initiation of efavirenz-based cART is high in Tanzanian HIV patients. Risk of neuropsychiatric manifestations is lower in HIV patients co-treated with rifampicin containing anti-TB compared to those treated with efavirenz-based cART only.

Prolyl Hydroxylase Inhibition Enhances Liver Regeneration Without Induction of Tumor Growth.

OBJECTIVE: We sought to assess whether pharmacological inhibition of hypoxia-inducible transcription factor (HIF)-prolyl hydroxylase enzymes (PHD1, PHD2, and PHD3) is a suitable strategy to stimulate liver regeneration after partial hepatectomy for colorectal liver metastases (CRLM). BACKGROUND: Liver regeneration occurs in a hypoxic environment. PHD1 to PHD3 are molecular oxygen sensors and increasingly considered as putative therapeutic targets. However, little is known about the effect of pharmacological PHD inhibition on tumor expansion, and on liver regeneration after surgical resection. METHODS: Various mouse models of liver regeneration after extended partial hepatectomy and portal vein ligation for multiple bilobar CRLM were applied to assess the effect of the small molecule pan-PHD inhibitor ethyl-3,4-dihydroxybenzoate (EDHB) on liver regeneration and metastatic tumor growth. Metabolism and biodistribution of EDHB were analyzed using liquid chromatography coupled to tandem mass spectrometry. RESULTS: EDHB selectively augmented liver regeneration after partial hepatectomy and portal vein ligation, and increased the expression of cell cycle-promoting cyclin proteins, without enhancing metastatic tumor growth. Systemically administered EDHB and its active metabolite 3,4-dihydroxybenzoic acid accumulated in the liver to selectively induce hepatoprotective effects in the liver, but not in tumor tissue, without humoral adverse effects. CONCLUSIONS: Pharmacological inhibition of PHDs using EDHB might represent a novel and safe strategy in the treatment of multiple bilobar CRLM.

Systemic exposure of topical erythromycin in comparison to oral administration and the effect on cytochrome P450 3A4 activity.

AIMS: Erythromycin is a macrolide antibiotic, which is frequently used as a topical formulation for the treatment of acne. It is also known as an inhibitor of the cytochrome P450 (CYP) isoenzyme 3A4. In this study, the systemic availability of topical erythromycin, hence the influence on the activity of CYP3A, is evaluated in comparison to orally administered erythromycin. METHODS: Sixteen healthy volunteers received consecutively topical (two applications of 800 mg) and oral erythromycin (two dose groups, 250 and 1000 mg, with n = 8) to assess erythromycin pharmacokinetics. A microdose of midazolam (3 µg orally) was used to determine the effect on CYP3A activity. RESULTS: After topical administration, erythromycin was detected in the plasma of every participant without causing a statistically significant alteration of CYP3A activity. After oral administration, the dose-normalized erythromycin exposure (AUC∞ ) was 1335 h ng ml(-1) after 250 mg and 3-fold higher after the 1000 mg dose (4051 h ng ml(-1); P < 0.01), suggesting nonlinear pharmacokinetics of erythromycin. Both oral doses inhibited CYP3A activity; midazolam clearance was decreased to 61% (250 mg) and 21% (1000 mg). The relationship between erythromycin exposure and CYP3A activity (Hill equation) revealed a 50% reduction of CYP3A activity by an erythromycin AUC∞ of 2106 h ng ml(-1). CONCLUSIONS: Topical erythromycin did not cause clinically relevant CYP3A alterations, although low systemic availability of erythromycin was observed. This supports the assumption that treatment with topical erythromycin is not critical in terms of CYP3A inhibition. Furthermore, substantial nonlinearity of erythromycin pharmacokinetics after two different oral doses was observed, possibly due to autoinhibition.

Clarithromycin substantially increases steady-state bosentan exposure in healthy volunteers.

AIMS: The aim of this study was to assess the effect of the cytochrome P450 (CYP) 3A4 and organic anion-transporting polypeptide (OATP) 1B1 inhibitor clarithromycin on the pharmacokinetics of bosentan. We also aimed to evaluate the impact of CYP2C9 and SLCO1B1 (encoding for OATP1B1) genotypes and their combination. METHODS: We assessed the effect of the OATP and CYP3A inhibitor clarithromycin on bosentan pharmacokinetics at steady state and concurrently quantified changes of CYP3A activity using midazolam as a probe drug. Sixteen healthy volunteers received therapeutic doses of bosentan (125 mg twice daily) for 14 days and clarithromycin (500 mg twice daily) concomitantly for the last 4 days, and bosentan pharmacokinetics was assessed on days 1, 10 and 14. RESULTS: Clarithromycin significantly increased bosentan area under the plasma concentration-time curve of the dosing interval 3.7-fold and peak concentration 3.8-fold in all participants irrespective of the genotype. Clarithromycin also reduced CYP3A activity (midazolam clearance) in all participants; however, these changes were not correlated to the changes of bosentan clearance. CONCLUSIONS: Clarithromycin substantially increases the exposure to bosentan, suggesting that dose reductions may be necessary.

Importance of ethnicity, CYP2B6 and ABCB1 genotype for efavirenz pharmacokinetics and treatment outcomes: a parallel-group prospective cohort study in two sub-Saharan Africa populations.

OBJECTIVES: We evaluated the importance of ethnicity and pharmacogenetic variations in determining efavirenz pharmacokinetics, auto-induction and immunological outcomes in two African populations. METHODS: ART naïve HIV patients from Ethiopia (n = 285) and Tanzania (n = 209) were prospectively enrolled in parallel to start efavirenz based HAART. CD4+ cell counts were determined at baseline, 12, 24 and 48 weeks. Plasma and intracellular efavirenz and 8-hydroxyefvairenz concentrations were determined at week 4 and 16. Genotyping for common functional CYP2B6, CYP3A5, ABCB1, UGT2B7 and SLCO1B1 variant alleles were done. RESULT: Patient country, CYP2B6*6 and ABCB1 c.4036A>G (rs3842A>G) genotype were significant predictors of plasma and intracellular efavirenz concentration. CYP2B6*6 and ABCB1 c.4036A>G (rs3842) genotype were significantly associated with higher plasma efavirenz concentration and their allele frequencies were significantly higher in Tanzanians than Ethiopians. Tanzanians displayed significantly higher efavirenz plasma concentration at week 4 (p<0.0002) and week 16 (p = 0.006) compared to Ethiopians. Efavirenz plasma concentrations remained significantly higher in Tanzanians even after controlling for the effect of CYP2B6*6 and ABCB1 c.4036A>G genotype. Within country analyses indicated a significant decrease in the mean plasma efavirenz concentration by week 16 compared to week 4 in Tanzanians (p = 0.006), whereas no significant differences in plasma concentration over time was observed in Ethiopians (p = 0.84). Intracellular efavirenz concentration and patient country were significant predictors of CD4 gain during HAART. CONCLUSION: We report substantial differences in efavirenz pharmacokinetics, extent of auto-induction and immunologic recovery between Ethiopian and Tanzanian HIV patients, partly but not solely, due to pharmacogenetic variations. The observed inter-ethnic variations in efavirenz plasma exposure may possibly result in varying clinical treatment outcome or adverse event profiles between populations.

Liver enzyme abnormalities and associated risk factors in HIV patients on efavirenz-based HAART with or without tuberculosis co-infection in Tanzania.

OBJECTIVES: To investigate the timing, incidence, clinical presentation, pharmacokinetics and pharmacogenetic predictors for antiretroviral and anti-tuberculosis drug induced liver injury (DILI) in HIV patients with or without TB co-infection. METHODS AND FINDINGS: A total of 473 treatment naïve HIV patients (253 HIV only and 220 with HIV-TB co-infection) were enrolled prospectively. Plasma efavirenz concentration and CYP2B6*6, CYP3A5*3, *6 and *7, ABCB1 3435C/T and SLCO1B1 genotypes were determined. Demographic, clinical and laboratory data were collected at baseline and up to 48 weeks of antiretroviral therapy. DILI case definition was according to Council for International Organizations of Medical Sciences (CIOMS). Incidence of DILI and identification of predictors was evaluated using Cox Proportional Hazards Model. The overall incidence of DILI was 7.8% (8.3 per 1000 person-week), being non-significantly higher among patients receiving concomitant anti-TB and HAART (10.0%, 10.7 per 1000 person-week) than those receiving HAART alone (5.9%, 6.3 per 1000 person-week). Frequency of CYP2B6*6 allele (p = 0.03) and CYP2B6*6/*6 genotype (p = 0.06) was significantly higher in patients with DILI than those without. Multivariate cox regression model indicated that CYP2B6*6/*6 genotype and anti-HCV IgG antibody positive as significant predictors of DILI. Median time to DILI was 2 weeks after HAART initiation and no DILI onset was observed after 12 weeks. No severe DILI was seen and the gain in CD4 was similar in patients with or without DILI. CONCLUSIONS: Antiretroviral and anti-tuberculosis DILI does occur in our setting, presenting early following HAART initiation. DILI seen is mild, transient and may not require treatment interruption. There is good tolerance to HAART and anti-TB with similar immunological outcomes. Genetic make-up mainly CYP2B6 genotype influences the development of efavirenz based HAART liver injury in Tanzanians.

Sildenafil preserves lung endothelial function and prevents pulmonary vascular remodeling in a rat model of diastolic heart failure.

BACKGROUND: Pulmonary hypertension as a frequent complication of left heart disease (PH-LHD) is characterized by lung endothelial dysfunction and vascular remodeling. Although PH-LHD contributes to morbidity and mortality in heart failure, established therapies for PH-LHD are lacking. We tested the effect of chronic sildenafil treatment in an experimental model of PH-LHD. METHODS AND RESULTS: In Sprague-Dawley rats, PH-LHD was induced by supracoronary aortic banding. Oral sildenafil treatment (60 mg/kg daily) was initiated after 7 days, and lung endothelial function (n=5), vascular remodeling, and right ventricular function (n=11 each) were analyzed 9 weeks after banding. As compared with sham-operated controls, aortic banding induced pulmonary hypertension and lung endothelial dysfunction evident as lack of endothelial nitric oxide production and endothelium-dependent vasodilation. These changes were associated with an increased pulmonary vascular resistance, medial thickening, and biventricular cardiac hypertrophy. Sildenafil treatment largely attenuated these pathological changes and was not associated with detectable adverse effects pertinent to lung vascular barrier function, edema formation, or systemic hemodynamics. CONCLUSIONS: Our data identify sildenafil as a promising therapy for PH-LHD. In light of its documented protective effects at the myocardial level in heart failure, sildenafil presents a particularly attractive strategy in that it simultaneously targets cardiac remodeling and secondary PH-LHD.

The NK1 receptor antagonist aprepitant does not alter the pharmacokinetics of high-dose melphalan chemotherapy in patients with multiple myeloma.

AIMS: The objective of this investigation was to assess the effect of aprepitant on the pharmacokinetics of high-dose melphalan used as conditioning therapy before blood stem cell transplantation in multiple myeloma. METHODS: Aprepitant (125 mg) or placebo was administered 1 h before melphalan therapy (1 h infusion of 100 mg m⁻²). Eleven plasma samples were obtained over 8 h and melphalan was quantified using an LC/MS/MS method. Standard pharmacokinetic parameters were calculated and nonparametric testing was applied to assess the differences between aprepitant and placebo treatment. RESULTS: Twenty patients received placebo and 10 patients aprepitant treatment. There were no differences observed for C(max) at the end of melphalan infusion (placebo 3431 ± 608 ng ml⁻¹ vs. aprepitant 3269 ± 660 ng ml⁻¹). In addition, AUC and terminal elimination half-life were not changed by aprepitant. Total clearance of melphalan was 304 ± 58 ml min⁻¹ m⁻² (placebo) which was not influenced by aprepitant (288 ± 78 ml min⁻¹ m⁻²). CONCLUSIONS: The administration of the NK1 receptor antagonist aprepitant 1 h before a high-dose chemotherapy does not influence the exposure and the elimination of melphalan. Therefore, oral administration of 125 mg aprepitant 1 h before melphalan infusion does not alter the disposition of intravenously administered melphalan.

High absolute bioavailability of methylene blue given as an aqueous oral formulation.

PURPOSE: Methylene blue (MB) has recently been reevaluated for malaria treatment. With the aim of excluding treatment failures due to low bioavailability, we have investigated the absolute bioavailability of MB given as an aqueous oral formulation and its interaction with chloroquine (CQ). METHODS: A phase I study in 16 healthy individuals was performed as a monocenter prospective open randomized intra-individual cross-over comparison of MB single doses [50 mg intravenous (i.v.), 500 mg orally, separated by a 1-week wash-out]. After a second week, the group was split for a randomized parallel group comparison of CQ 750 mg administered orally alone or combined with 500 mg MB orally. RESULTS: Mean MB plasma area under the substrate concentration-time curve (AUC 0-infinity) was 7,639 +/- 3,384 ng/mL*h and 51,171 +/- 17,147 ng/mL*h after i.v. and oral administration, respectively (dosage 1:10), and 76,897 +/- 46,037 ng/mL*h after MB combined with CQ. The absolute bioavailability was 72.3 +/- 23.9%. Co-administration with CQ significantly increased MB plasma concentrations (p

Marked differences in the prevalence of chloroquine resistance between urban and rural communities in Burkina Faso.

BACKGROUND: Chloroquine (CQ) resistance has reached high levels in Africa in recent years. Little is known about variations of resistance between urban and rural areas. OBJECTIVES: To compare the rates of in vivo resistance to CQ and the prevalences of the main molecular marker for CQ resistance among young children from urban and rural areas in Burkina Faso. METHODS: The current analysis used the frame of a randomized controlled trial (ISRCTN27290841) on the combination CQ-methylene blue (MB) (n=177) compared to CQ alone (n=45) in young children with uncomplicated malaria. We examined clinical and parasitological failure rates as well as the prevalence of the Plasmodium falciparum chloroquine resistance transporter gene (pfcrt) T76 mutation. RESULTS: Clinical and parasitological failure rates of CQ-MB differed significantly between urban (70%) and rural areas (29%, p<0.0001). Likewise, CQ failure rates were higher in the urban setting. Matching this pattern, pfcrt T76 was more frequently seen among parasite strains from urban areas (81%) when compared to rural ones (64%, p=0.01). In the presence of parasites exhibiting pfcrt T76, the odds of overall clinical failure were increased to 2.6-fold ([1.33, 5.16], p(LR)=0.005). CQ was detected at baseline in 21% and 2% of children from the urban and the rural study area, respectively (p(Chi)=0.002). CONCLUSION: Even within circumscribed geographical areas, CQ efficacy can vary dramatically. The differences in the prevalence of pfcrt T76 and in CQ failure rates are probably explained by a higher drug pressure in the urban area compared to the rural study area. This finding has important implications for national malaria policies.

Comparative bioavailability of the microemulsion formulation of cyclosporine (Neoral) with a generic dispersion formulation (Cicloral) in young healthy male volunteers.

The aim of this study was to compare the bioavailability of cyclosporine (CyA) from the generic dispersion formulation Cicloral (CIC) with the microemulsion formulation Neoral (NEO) and the original Sandimmune (SIM) capsules after single doses of 100, 300, or 600 mg of drug, respectively. The study was performed according to an open 3-period cross-over design with 12 young healthy male volunteers for each dosage. The concentrations of CyA and its main metabolites were determined by high performance liquid chromatography in whole blood and urine up to 48 hours postdosing. Peak concentrations and area under the time-concentration curve were greater for the NEO and CIC formulations compared with SIM, and the mean bioavailability of CIC was significantly (P<0.05) lower compared with NEO. The bioavailability of SIM compared with NEO was 54% to 71%, in agreement with previous results. Bioequivalence was not demonstrated between CIC (test) and NEO (reference) as the 90% confidence intervals were outside the 80% to 125% guidelines based on log-transformed AUCs, and were 75.2% to 87.7% at 100 mg, 79.2% to 91.8% at 300 mg, and 76.6% to 94.5% at 600 mg doses. The respective values for Cmax were 78.9% to 94.6%, 80.7% to 95.0%, and 71.4% to 84.1%. A good correlation was demonstrated between the urinary recovery of CyA and the AUC4. Therefore, the urinary recovery of CyA may be helpful as a surrogate parameter for the systemic exposure of patients to CyA. Whereas the relative amount of hydroxylated metabolites (AM1, AM9, AM1c) was similar for all formulations and doses, the urinary recovery of the N-demethylated metabolite AM4N decreased with increasing dose indicating saturable metabolism. No relationship could be demonstrated between CYP3A activity using dextromethorphan as a probe for the metabolic clearance of CyA.

Influence of lipid lowering fibrates on P-glycoprotein activity in vitro.

Statin/fibrate combinations are frequently used to treat mixed dyslipidemia. However, these combinations may cause life-threatening drug interactions (e.g. rhabdomyolysis) possibly induced by modifications of cytochrome P450 isozyme activities. Some statins are also transported by P-glycoprotein (Pgp) and may act as inhibitors of this drug efflux pump. So far, nothing is known about possible Pgp modulating effects of fibrates. We tested whether gemfibrozil, fenofibrate, fenofibric acid, and bezafibrate inhibit Pgp in vitro using a calcein acetoxymethylester (calcein-AM) uptake assay and confocal laser scanning microscopy with bodipy-verapamil as substrate in L-MDR1 cells, which overexpress human Pgp. In uptake assays in cells with (L-MDR1) and without (LLC-PK1) human Pgp we also investigated whether these compounds are transported by Pgp. Intracellular concentrations were measured by liquid chromatography tandem mass spectrometry. Of the tested fibrates, only fenofibrate increased calcein-AM uptake into cells indicating an inhibition of Pgp mediated transport by this compound. The potency of fenofibrate (mean+/-SD: 7.1+/-3.2 microM), evaluated by calculating the concentration needed to double baseline fluorescence (f2), was similar to that of simvastatin (5.8+/-1.5 microM), lovastatin (10.1+/-1.0), and verapamil (4.7+/-0.8 microM). For simvastatin and fenofibrate Pgp inhibition was confirmed with confocal laser scanning microscopy. Fenofibrate, fenofibric acid, gemfibrozil, and bezafibrate showed no difference in the cellular uptake between LLC-PK1 and L-MDR1, indicating that the tested fibrates are not Pgp substrates. In conclusion, this study demonstrates that fenofibrate inhibits Pgp in vitro with a potency similar to simvastatin.