Thalidomide does not interact with P-glycoprotein

Background: There is growing clinical interest in thalidomide for the treatment of various disorders due to its anti-inflammatory, immunomodulatory, and anti-angiogenic properties. In numerous clinical trials thalidomide is used as an adjunct to standard therapy. Therefore, clinicians should be aware of all possible drug-drug interactions that might occur with this drug. P-glycoprotein (P-gp), a drug efflux transporter that is expressed in many tissues, is the cause of several drug-drug interactions. P-gp induction or inhibition can lead to ineffective therapy or side-effects. In this study, we investigated thalidomide's potential to cause drug-drug interactions on the level of P-gp. Methods: LS180 cells were incubated with thalidomide for 72h in order to determine P-gp induction using real-time RT-PCR. A human leukaemia cell line over-expressing MDR1 (CCRF-CEM/MDR1) was used to measure uptake of rhodamine 123, a P-gp substrate, in the presence of thalidomide. Dose-dependent and bi-directional transport of thalidomide through Caco-2 cell monolayers was performed to assess site-directed permeability. Transport rates were determined using HPLC including chiral separation of the thalidomide enantiomers. Results: Thalidomide did not induce P-gp expression in LS180 cells. The uptake of rhodamine 123 in CCRF cells over-expressing MDR1 was not influenced by co-incubation with thalidomide. The transport through Caco-2 monolayers was linear and the permeability was similar for both directions. No differences between the thalidomide enantiomers were observed. Conclusions: Our study indicates that thalidomide is neither a substrate, nor an inhibitor or an inducer of P-gp. Therefore, P-gp-related drug-drug interactions with thalidomide are not likel

Decreased expression of breast cancer resistance protein in the duodenum in patients with obstructive cholestasis

Background/Aims: The expression of transporters involved in bile acid homeostasis is differentially regulated during obstructive cholestasis. Since the drug efflux transporter breast cancer resistance protein (BCRP) is known to transport bile acids, we investigated whether duodenal BCRP expression could be altered during cholestasis. Methods: Using real-time RT-PCR analysis we determined mRNA expression levels in duodenal tissue of 19 cholestatic patients. Expression levels were compared to 14 healthy subjects. BCRP protein staining was determined in biopsies of 6 cholestatic and 6 healthy subjects by immunohistochemistry. Results: We found that in patients with obstructive cholestasis mean duodenal BCRP mRNA levels were significantly reduced to 53% and mean protein staining was reduced to 57%. Conclusions: BCRP, a transporter for bile acids and numerous drugs, appears to be down-regulated in the human duodenum during cholestasis. The clinical impact of these results has to be investigated in further studies. Copyright (c) 2006 S. Karger AG, Basel

Role of fat hydrolysis in regulating glucagon-like Peptide-1 secretion

Context: Glucagon-like peptide-1 (GLP-1) is produced by specialized cells in the gut and secreted in response to carbohydrates and lipids. The mechanisms regulating fat-stimulated GLP-1 release have, however, not been clarified in detail. Aim: We aimed to investigate the effect of intraduodenal (ID) fat hydrolysis on GLP-1 release and test whether the signal is mediated through cholecystokinin (CCK)-1 receptors. Design and Setting: Thirty-four healthy, male ambulatory volunteers were studied in three consecutive, randomized, double blind, crossover studies. Intervention: There were three interventions: 1) 12 subjects received an ID fat infusion with or without orlistat, an irreversible inhibitor of gastrointestinal lipases, in comparison with vehicle; 2) 12 subjects received ID sodium oleate (C18:1), ID sodium caprylate (C8:0), or ID vehicle; and 3) 10 subjects received ID sodium oleate with and without the CCK-1 receptor antagonist dexloxiglumide or ID vehicle plus iv saline (placebo). The effect of these treatments on GLP-1 concentrations and CCK release was quantified. Results: The following results were reached: 1) ID fat induced significant increase in GLP-1 concentrations (P > 0.004), and inhibition of fat hydrolysis by orlistat abolished this effect; 2) sodium oleate significantly stimulated GLP-1 release (P > 0.008), whereas sodium caprylate was ineffective compared with controls; and 3) dexloxiglumide administration abolished the effect of sodium oleate on GLP-1. ID fat or sodium oleate significantly stimulated plasma CCK (P > 0.006 and P > 0.004) compared with saline, whereas sodium caprylate did not. Conclusion: Generation of long-chain fatty acids through hydrolysis of fat is a critical step for fat-induced stimulation of GLP-1 in humans; the signal is mediated via CCK release and CCK-1 receptors

Ефекти екстракту Циміцифуги гроновидної Ze 450 (сімідона) в лікуванні клімактеричної симптоматики – обсерваційне дослідження

Background: Root extracts of Cimicifuga racemosa (L.) Nutt. have been successfully used in the treatment of climacteric complaints.Method: In this observational study, Cimicifuga racemosa (CR) extract Ze 450 was studied in 442 unselected ambulatory female outpatients with menopausal complaints under daily practice conditions. Physicians were suggested to treat patients for the first 3 months with 13 mg/d CR (high dose) and to continue over additional 6 months either with this treatment or to switch to 6.5 mg/d CR (low dose). The choice of treatment and its dose, however, was fully at the discretion of the physician.Results: After 3-months treatment with high dose, symptom severity (Kupperman Menopause Index, KMI) decreased significantly (p < 0.001) from baseline values. Continuation of treatment with high dose or low dose decreased total KMI and its sub-item scores further (high dose, low dose: p < 0.001). However, more patients (84.9%) responded to high dose than to low dose (78.4%) and showed an improvement of symptoms (p = 0.011).Conclusion: This observational study demonstrated that treatment with CR in unselected patients with climacteric complaints under the conditions of daily practice resulted in a significant improvement of menopausal symptoms assessed by the total KMI score and its sub-item scores with an effect size similar to that in a previous randomized, controlled clinical trial. Treatment with both doses Ze 450 (low and high dose) is well tolerated by patients and has an additional positive effect in extending the treatment for more than 3 months, with a further decrease in the total KMI. However, prolonged treatment with a high dose is more efficient, since it, in contrast to the low dose therapy, can significantly reduce each of menopausal symptoms.В представленном в статье обсервационном исследовании был изучен экстракт Цимицифуги кистевидной (Cimicifuga racemosa, СR) Ze 450, экстракты корневищ которой успешно использовались в качестве лечения климактерической симптоматики.В исследовании, которое проводилось в условиях повседневной практики, приняли участие 442 неотобранные амбулаторные пациентки с климактерическими жалобами. Врачам было предложено начать лечение с дозировки CR 13 мг/день (высокая доза) в течение первых трех месяцев и продолжить лечение еще в течение 6 месяцев либо дозировкой 13 мг/день (высокая доза), либо переключиться на дозировку 6,5 мг/день (низкая доза). В то же время выбор метода лечения и дозы полностью контролировал врач.После 3 месяцев лечения высокой дозой Ze 450 тяжесть климактерических симптомов, определяемых по менопаузальному индексу Куппермана (МИК), значительно снизилась (p < 0,001) по отношению к исходным значениям. Как видно из результатов исследования, продолжение лечения высокой или низкой дозой дополнительно уменьшает общий МИК и тяжесть отдельных симптомов (p < 0,001). Однако доля отклика на лечение была выше в группе высокой дозы (84,9%), чем в группе низкой (78,4%).Данное обсервационное исследование, проведенное в условиях ежедневной практики, продемонстрировало, что лечение экстрактом Ze 450 у неотобранных пациенток с климактерической симптоматикой приводит к значительному улучшению менопаузальных симптомов, оцениваемых с помощью общего МИК. Это совпадает с данными, полученными в предыдущем рандомизированном контролируемом клиническом испытании, проведенном авторами статьи. Лечение обеими дозировками Ze 450 (низкая и высокая доза) хорошо переносится пациентками и имеет дополнительный положительный эффект при продлении терапии на период более 3 месяцев с дальнейшим снижением общего МИК. Тем не менее, длительное лечение высокой дозой более эффективно, поскольку оно, в отличие от терапии низкой дозой, способно значительно снизить проявления каждого из менопаузальных симптомов.У представленому в статті обсерваційному дослідженні був вивчений екстракт Циміцифуги гроновидної (Cimicifuga racemosa, СR) Ze 450, екстракти кореневищ якої успішно використовувалися як лікування клімактеричної симптоматики.В дослідженні, яке проводилося в умовах повсякденної практики, взяли участь 442 невідібрані амбулаторні пацієнтки з клімактеричними скаргами. Лікарям було запропоновано розпочати лікування з дозування CR 13 мг на день (висока доза) протягом перших трьох місяців і продовжити лікування ще протягом 6 місяців або дозуванням 13 мг/день (висока доза), або обрати дозування 6,5 мг/день (низька доза). У той же час вибір методу лікування і дози повністю контролював лікар.Після 3 місяців лікування високою дозою Ze 450 тяжкість клімактеричних симптомів, які визначали за менопаузальним індексом Куппермана (МІК), значно знизилася (p < 0,001) по відношенню до початкових значень. Як видно з результатів дослідження, продовження лікування високою або низькою дозою додатково зменшує загальний МІК і тяжкість окремих симптомів (p < 0,001). Однак частка відгуку на лікування була вищою в групі високої дози (84,9%), ніж у групі низької (78,4%).Дане обсерваційне дослідження, проведене в умовах щоденної практики, продемонструвало, що лікування екстрактом Ze 450 у невідібраних пацієнток з клімактеричною симптоматикою призводить до значного поліпшення менопаузальних симптомів, які оцінюються за допомогою загального МІК. Це збігається з даними, отриманими в попередньому рандомізованому контрольованому клінічному дослідженні, проведеному авторами статті. Лікування обома дозуваннями Ze 450 (низька і висока доза) добре переноситься пацієнтками і має додатковий позитивний ефект при продовженні терапії на період більше ніж 3 місяці з подальшим зниженням загального МІК. Проте тривале лікування високою дозою є більш ефективним, оскільки воно, на відміну від терапії низькою дозою, здатне значно знизити прояви кожного з менопаузальних симптомів

Pharmacokinetic evaluation of idebenone

IMPORTANCE OF THE FIELD: Idebenone is a synthetic short chain benzoquinone that acts as an electron carrier in the mitochondrial electron transport chain, thereby, facilitating the production of ATP. In addition, idebenone is an antioxidant and can inhibit lipid peroxidation and may protect cell membranes and mitochondria from oxidative damage. High dose idebenone (Catena(®)) is approved in Canada for the symptomatic treatment of Friedreich's ataxia and is currently under clinical investigation for use in a number of mitochondrial and neuromuscular diseases. AREAS COVERED IN THIS REVIEW: This review summarizes the pharmacology, pharmacokinetic and clinical efficacy/safety data of idebenone and its metabolites and provides an update of the clinical trials completed and in progress. WHAT THE READER WILL GAIN: Following oral administration, idebenone is rapidly metabolized via oxidative shortening by a number CYP isoenzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4) to yield QS10, QS8, QS6 and QS4. Idebenone and these metabolites concomitantly undergo conjugation via glucuronidation and sulfatation to yield conjugated moieties represented as idebenone-C, QS10-C, QS8-C, QS6-C and QS4-C. Previous reports in the literature were only able to quantify plasma concentrations of idebenone measured together with its conjugates. More recently, highly sensitive and specific liquid chromatography method with tandem mass spectrometric methods have been developed, allowing the quantification of the parent molecule idebenone and its main metabolite QS10, separately. TAKE HOME MESSAGE: After absorption, idebenone is rapidly metabolized by first pass metabolism and shows dose-proportional pharmacokinetics in healthy subjects in daily doses up to 2250 mg. The recent development of advanced analytical techniques allows the detection of idebenone and unconjugated metabolites in plasma and consequently opens the possibility for evaluation of pharmacokinetic/pharmacodynamic relationships which will be helpful to further understand the metabolism and therapeutic potential of idebenone. In clinical studies, idebenone was safe and well tolerated at doses up to 2250 mg/day

A New Intestinal Cell Culture Model To Discriminate the Relative Contribution of P-gp and BCRP on Transport of Substrates Such as Imatinib

P-glycoprotein (P-gp/MDR1/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) play an important role in transport of a wide variety of endogenous compounds, drugs and toxins. Transport of some drugs, for example the tyrosine kinase inhibitor imatinib, is influenced by both P-gp and BCRP. Establishing an intestinal Caco-2 cell culture model with specific knock-downs of P-gp and BCRP and double knock-down of both proteins, we aimed to elucidate the impact of each transporter on transport of imatinib. Stable single and double knock-downs of P-gp and BCRP were obtained by RNA interference (RNAi). Transporter expression was measured on RNA and protein level using real-time RT-PCR and Western blot, respectively. Functional activity was quantified by transport of specific substrates across Caco-2 cells. MDR1 and BCRP mRNA expression was reduced to 75% and 90% compared to wild-type control in single MDR1- and BCRP-knock-down clones, respectively. In double knock-down clones, MDR1 expression decreased to 95% and BCRP expression to 80%. Functional activity of P-gp and BCRP was diminished as transport of the P-gp-specific substrate (3)H-digoxin and the BCRP-specific substrate (14)C-PhIP was augmented in the opposite direction, when the respective transporter was knocked down. Similar effects were observed by chemical inhibition of the respective transporter. Bidirectional transport studies with (14)C-imatinib revealed an abrogation of asymmetric transport when P-gp was knocked down, either in single or double knock-down clones compared to wild-type cells. This was not observed in single BCRP-knock-down clones. In conclusion, this newly established cell system with single and concomitant knock-down of P-gp and BCRP can be used to quantify the specific partial impact of the transporters on transport of substrates that are transported by both proteins. For imatinib transport, the contribution of P-gp seems to be more important compared to BCRP in this Caco-2 cell sys

Induction of Cytochrome P450 3A4 and P-Glycoprotein by the Isoxazolyl-Penicillin Antibiotic Flucloxacillin

Clinical findings indicate that co-administration of the isoxazolyl-penicillin flucloxacillin with cyclosporine may reduce the plasma concentrations of cyclosporine. We have explored in the present study if induction of cytochrome P450 3A4 or P-glycoprotein may offer a mechanistic explanation of the observed effects. Flucloxacillin is neither an inhibitor nor a substrate of drug metabolizing cytochrome P450 isoenzymes (CYP3A4, 1A2, 2C9, 2C19 and 2D6) or P-glycoprotein as shown by an in vitro assay for CYP inhibition, a fluorescent indicator assay for P-glycoprotein inhibition and a functional P-glycoprotein ATPase assay. However, incubation of human LS 180 colorectal adenocarcinoma cells with flucloxacillin led to a dose-dependent induction of MDR1 as well as of CYP3A4 mRNA, which was also confirmed in primary human hepatocytes. At high concentrations, flucloxacillin activated the human Pregnane-X-Receptor, PXR, a ligand-dependent transcription factor that is the target of many drugs that induce CYP3A4, with consequences for the metabolism of other drugs. Liver microsomes from control rats or rats, which received for 3 consecutive days 100 mg/kg of oral flucloxacillin, were used to study the metabolism and metabolite pattern of midazolam, a model substrate of CYP 3A4. There was a trend towards a higher intrinsic microsomal clearance of midazolam using microsomes from flucloxacillin treated rats. In addition, there was a significant increase in the formation of the principal midazolam metabolites 1-hydroxy midazolam, 4-hydroxy midazolam and 1,4-dihydroxy midazolam as compared to controls. These findings indicate that flucloxacillin has the potential to induce expression of both CYP3A4 as well as P-glycoprotein, most likely through activation of the nuclear hormone receptor PXR. This would offer an explanation for the observed clinical drug-drug interactions between the antibiotic and cyclosporine