Bertrand Diquet

Comparison of pharmacokinetics and metabolism of desloratadine, fexofenadine, levocetirizine and mizolastine in humans

Absorption, distribution, metabolism and excretion of desloratadine, fexofenadine, levocetirizine, and mizolastine in humans have been compared. The time required to reach peak plasma levels (tmax) is shortest for levocetirizine (0.9 h) and longest for desloratadine (≥3 h). Steady‐state plasma levels are attained after about 6 days for desloratadine, 3 days for fexofenadine, 2–3 days for mizolastine and by the second day for levocetirizine. The apparent volume of distribution is limited for levocetirizine (0.4 L/kg) and mizolastine (1–1.2 L/kg), larger for fexofenadine (5.4–5.8 L/kg) and particularly large for desloratadine (≈ 49 l/kg). Fexofenadine and levocetirizine appear to be very poorly metabolized (≈ 5 and 14% of the total oral dose, respectively). Desloratadine and mizolastine are extensively metabolized. After administration of 14C‐levocetirizine to healthy volunteers, 85 and 13% of the radioactivity are recovered in urine and faeces, respectively. In contrast, faeces are the preferential route of excretion for 14C‐fexofenadine (80% vs. 11% of the radioactive dose in urine). The corresponding values are 41% (urine) and 47% (faeces) for 14C‐desloratadine, 84–95% (faeces) and 8–15% (urine) for 14C‐mizolastine. The absolute bioavailability is 50–65% for mizolastine; it is high for levocetirizine as the percentage of the drug eliminated unchanged in the 48 h urine is 77% of the oral dose; the estimation for fexofenadine is at least 33%; no estimation was found for desloratadine. Fexofenadine is a P‐glycoprotein (P‐gp) substrate and P‐gp is certainly involved both in the poor brain penetration by the compound and, at least partially, in a number of observed drug interactions. An interaction of desloratadine with P‐gp has been suggested in mice, whereas the information on mizolastine is very poor. The fact that levocetirizine is a substrate of P‐gp, although weak in an in vitro model, could contribute to prevent drug penetration into the brain, whereas it is unlikely to be of any clinical relevance for P‐gp‐mediated drug interactions.

Selection of Drug-Resistant Variants in the Female Genital Tract of Human Immunodeficiency Virus Type 1-Infected Women Receiving Antiretroviral Therapy

We investigated human immunodeficiency virus (HIV) type 1 RNA, proviral DNA, and antiretroviral drug-resistant variants in cervicovaginal secretions of HIV-1-infected women receiving antiretroviral therapy. The prevalence of detectable HIV-1 RNA in genital secretions was inversely related to the number of antiretroviral drugs taken by the patients. Proviral DNA was detected in approximately half of all samples of cervicovaginal secretions from HIV-1-infected women, regardless of the presence or absence of HIV-1 RNA in cervicovaginal secretions and of the antiretroviral regimen. In cervicovaginal secretions of most women with persisting genital viral replication, HIV variants exhibiting mutations associated with drug resistance against protease and reverse-transcriptase pol genes were found. Our observations indicate that antiretroviral therapy is not effective in purging the female genital tract of cell-associated provirus and that antiretroviral drugs that penetrate the female genital tract at suboptimal concentrations exert a potent selective pressure on genital HIV variants when local replication of free HIV-1 RNA persists.

Potentiation of Vitamin K Antagonists by High-Dose Intravenous Methylprednisolone

Pulse high-dose intravenous methylprednisolone is widely used for the treatment of flares in inflammatory and autoimmune diseases (1). Most of these diseases carry a risk for venous and arterial occlusion (2-4). In addition, patients may have individual indications for oral anticoagulation that are independent of inflammatory disease, such as atrial fibrillation and mechanical prosthetic heart valves. Therefore, oral anticoagulants and methylprednisolone are often administered concomitantly in clinical practice. In early studies, oral anticoagulants had both enhanced (5) and diminished effects (6, 7) when given concurrently with oral corticosteroids. Corticosteroids are not thought to potentiate oral anticoagulants (8). In a patient receiving oral anticoagulation, we observed a sharp increase in the international normalized ratio (INR) after concomitant administration of methylprednisolone. This observation, and the lack of relevant published data, prompted us to conduct a prospective study of the potential interaction of methylprednisolone with oral anticoagulants. Methods Patients We studied 10 consecutive patients who were referred to the internal medicine department of Piti-Salptrire Hospital in Paris, France. The 4 women and 6 men (mean age, 51 years [range, 20 to 79 years]) were taking oral anticoagulants and received methylprednisolone for giant-cell arteritis (n=2), autoimmune thrombocytopenic purpura (n=2), vasculitis (n=3), multiple myeloma (n=1), lupus flare (n=1), or mediastinal fibrosis (n=1). Methylprednisolone was given in the form of 1 g or 500 mg of hemisuccinate methylprednisolone (Solu-Medrol, Pharmacia & Upjohn, Saint-Quentin en Yvelines, France) reconstituted in 5% dextrose in water (total volume, 250 mL) and was infused intravenously over 1 hour. All 10 patients were taking vitamin K antagonists (fluindione [n=8] and acenocoumarol [n=2]) for atrial fibrillation (n=3), the antiphospholipid syndrome (n=3), thromboembolic events (n=2), distal limb ischemia (n=1), or the superior vena cava syndrome (n=1). Daily doses were 4 mg of acenocoumarol (n=2) and 5 mg (n=1), 10 mg (n=2), 20 mg (n=3), 25 mg (n=1), or 40 mg (n=1) of fluindione; these doses had not been increased in the 10 days before administration of the first methylprednisolone pulse. Except for the first patient, informed consent was obtained in each case before study enrollment. The control group consisted of five consecutive patients (mean age, 50 years [range, 21 to 80 years]) who were receiving methylprednisolone for giant-cell arteritis (n=2), lupus flare (n=1), idiopathic retroperitoneal fibrosis (n=1), or Crohn disease (n=1). Controls did not receive oral anticoagulants before or during methylprednisolone administration. All of the cases were reported to the Paris-Piti-Salptrire regional pharmacovigilance center. Concomitant Medications Concomitant medications were screened for drugs known to potentiate oral anticoagulants (8, 9). Two patients were receiving concomitant amiodarone therapy, but the doses had not been modified during the 6 months before the study began and were not modified during the study. Three patients were receiving acetaminophen, but the weekly dose was less than 4550 mg (the minimum dose that has been found to increase the INR) during the week before methylprednisolone administration and throughout the study (10). Clotting Tests The prothrombin time, interpreted as the INR, was measured by using the Simplastin Excel S reagent with an international sensitivity index of 1.31 (Organon Teknika Corp., Durham, North Carolina). Factors II, VII, IX, and X were routinely measured by using an STA IX analyzer (Diagnostica Stago, Asnires-sur-Seine, France), as described elsewhere (11). Levels of protein C and free protein S were assayed by using an amidolytic method (Berichrom Protein C, Dade Behring, Liederbach, Germany) and a procoagulant method (Protein S Reagent, Dade Behring), respectively, on a Behring Coagulation Timer (Dade Behring). Total (free and protein-bound) fluindione levels were assayed by using high-performance liquid chromatography, as described elsewhere (12). Results International Normalized Ratio after Administration of High-Dose Intravenous Methylprednisolone For all patients, the target INR was 2.0 to 4.0. The INR was checked during the 12 hours before methylprednisolone infusion. At baseline, the mean INR was 2.75 (range, 2.02 to 3.81). In all patients, the INR increased to a mean of 8.04 (range, 5.32 to 20.0) after methylprednisolone administration (Figure 1). The maximum increase in the INR occurred after a mean of 92.7 hours (range, 29 to 156 hours). Because the INR reached life-threatening levels in five patients (patients 1, 2, 4, 6, and 8), we administered vitamin K, which decreased the INR in 4 to 12 hours (Figure 1). In four other patients (patients 3, 5, 7, and 9), oral anticoagulation was discontinued and the INR returned to baseline in 36 to 48 hours (Figure 1). Figure 1. Potentiation of vitamin K antagonists by intravenous high-dose methylprednisolone in patients 1 through 10. INR Levels of protein C; free protein S; and vitamin K-dependent factors II, VII, IX, and X decreased as the INR increased. However, levels of factor V remained normal in every case (data not shown). International Normalized Ratio after Methylprednisolone Alone To determine whether INR elevation was caused by the action of methylprednisolone on clotting factors, we assessed the prothrombin time in five consecutive controls who received methylprednisolone (1 g/d for 3 days) without concomitant oral anticoagulation. The prothrombin time was checked every day and remained stable for 7 days after the first dose of methylprednisolone was administered (Figure 2). Figure 2. Lack of effect of intravenous high-dose methylprednisolone alone on prothrombin time in five controls. Elevation of the International Normalized Ratio after Concomitant Administration of Methylprednisolone and Oral Anticoagulation To rule out in vitro interference between methylprednisolone and INR reagents, we collected plasma from nine patients who were being treated with fluindione and added methylprednisolone at concentrations of 0 mg/L, 5 mg/L, and 20 mg/L (based on the peak concentration of methylprednisolone in vivo in patients treated with methylprednisolone [13]). The resulting INRs were not influenced by the baseline INR or by the dose of methylprednisolone added (data not shown). Total plasma fluindione concentrations were serially assayed in three patients (patients 6, 8, and 10). Fluindione concentrations and the INR always increased after methylprednisolone administration (Figure 1). Discussion To determine whether methylprednisolone potentiated oral anticoagulation, we studied variations of the INR in 10 consecutive patients who were taking oral anticoagulants and received methylprednisolone concomitantly. The INR increased sharply, exceeding 6.0 in almost all patients. In contrast, methylprednisolone alone did not interfere with clotting factors (prothrombin time). These results suggest that INR elevation was due to potentiation of oral anticoagulation by methylprednisolone. Although no bleeding complications occurred in this small series, the INR elevation was severe enough to warrant vitamin K supplementation or withdrawal of the vitamin K antagonist, and we were therefore unable to observe the maximum potential increase in the INR. Our data are in keeping with those of Kaufman (14), who described two patients with multiple sclerosis who were receiving warfarin: one for a prosthetic valve and one for pulmonary embolism. In these patients, the INR reached 10.0 and 12.0, respectively, after methylprednisolone administration. Of note, two patients in our study received acenocoumarol, a coumarin congener that chemically differs from warfarin only by its nitro group at the para position in the phenyl ring. Although our study included a small number of patients, it is unlikely that the INR increased because of spontaneous fluctuations in each patients response to oral anticoagulants. The INR reached 6 in almost all of our consecutive patients; however, in a recent study of 29 000 INRs observed during a 6-month period (15), only 85 exceeded 6.0. Furthermore, our patients did not have any of the conditions reported to increase the INR, such as alcoholism, liver disease, frequent modification of oral anticoagulant dose, and recent withdrawal or initiation of medications known to interact with oral anticoagulants. In a study of 55 625 INRs in which 131 patients had INRs that exceeded 8.0, one of two hemorrhage-related deaths involved a patient taking warfarin who was receiving high-dose steroids for vasculitis (16) . Although the precise mechanism of the interaction between methylprednisolone and oral anticoagulants is unclear, several lines of evidence strongly suggest that it is due to inhibition of oral anticoagulant catabolism by high-dose methylprednisolone. First, the increase in the INR observed after methylprednisolone administration occurred through a vitamin K-dependent pathway. The INR increased regardless of the anticoagulant used (acenocoumarol, warfarin, or fluindione, a noncoumarin indanedione anticoagulant that is common in Europe). In addition, this increase was rapidly reversed by administration of vitamin K (14). Second, because oral anticoagulants are almost completely absorbed from the gastrointestinal tract (9), it is unlikely that elevated fluindione concentrations were due to increased absorption. Third, because we measured total fluindione, it is unlikely that the elevated concentrations resulted from a change in the ratio between free and protein-bound fluindione. Fourth, methylprednisolone inhibits the cytochrome P450 enzyme system (17), which is involved in the metabolism of oral anticoagulants (18). It is therefore possible that high-dose methylprednisolone potentiates vitamin K antagonists by inhibiting thei

High-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) method for the simultaneous determination of diazepam, atropine and pralidoxime in human plasma

A high-performance liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS) procedure for the simultaneous determination of diazepam from avizafone, atropine and pralidoxime in human plasma is described. Sample pretreatment consisted of protein precipitation from 100microl of plasma using acetonitrile containing the internal standard (diazepam D5). Chromatographic separation was performed on a X-Terra MS C8 column (100mmx2.1mm, i.d. 3.5microm), with a quick stepwise gradient using a formate buffer (pH 3, 2mM) and acetonitrile at a flow rate of 0.2ml/min. The triple quadrupole mass spectrometer was operated in positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges of 1-500ng/ml for diazepam, 0.25-50ng/ml for atropine and 5-1000ng/ml for pralidoxime. The coefficients of variation were always <15% for both intra-day and inter-day precision for each analyte. Mean accuracies were also within +/-15%. This method has been successfully applied to a pharmacokinetic study of the three compounds after intramuscular injection of an avizafone-atropine-pralidoxime combination, in healthy subjects.

Phase II placebo-controlled trial of fozivudine tidoxil for HIV infection: pharmacokinetics, tolerability, and efficacy.

Fozivudine tidoxil (FZD) is a thioether lipid-zidovudine (ZDV) conjugate with anti-HIV activity demonstrated in vitro and in pilot phase I studies. To assess its safety, efficacy and pharmacokinetics, we conducted a multicenter, randomized, double-blind, placebo-controlled trial of FZD monotherapy in 72 HIV-infected patients who had not previously received antiretroviral therapy. In each dosage group (200 mg daily, 400 mg daily, 200 mg twice daily, 800 mg daily, 400 mg twice daily, and 600 mg twice daily), 12 patients were randomized to receive in a 10:2 ratio either FZD or a placebo for 4 weeks. Overall, FZD was well tolerated in all dosage groups; only 1 patient discontinued the drug, because of a moderate rise in aminotransaminase activity. HIV viral load fell in all the patients who were receiving FZD, except in the 200 mg daily group. The largest decrease (-0.67 log10) was observed in the 600 mg twice daily group. The plasma half-life was significantly longer (approximately 3.8 hours) than that of the parent drug ZDV. Exposure to ZDV, as reflected by the area under the time-concentration curve, was much lower after FZD than after ZDV administration. FZD thus appears to be as effective as and potentially better tolerated than ZDV during short-term administration and has the advantage of once daily intake.

Atenolol administration via a nasogastric tube after abdominal surgery: an unreliable route.

&bgr;-Adrenoceptor antagonists, especially atenolol, reduce perioperative cardiac morbidity. Because there are no data on the bioavailability of atenolol given by nasogastric tube in the postoperative period, we assessed the efficacy of this route of administration in 18 patients scheduled for abdominal surgery. We found a 36% reduction in the area under the atenolol concentration curve and a 46% reduction in the peak concentration of atenolol in the postoperative period compared with preoperative values. In addition, patients had more rapid mean heart rates on the second postoperative day compared with the day before surgery. We conclude that the administration of atenolol via nasogastric tube in the postoperative period does not result in adequate plasma concentrations.

Liposomal Encapsulation of Ganciclovir Enhances the Efficacy of Herpes Simplex Virus Type 1 Thymidine Kinase Suicide Gene Therapy against Hepatic Tumors in Rats

Suicide gene therapy based on ganciclovir (GCV) metabolism by transgene herpes simplex thymidine kinase (HSV-1 TK) has been used to selectively kill proliferating cells in clinical settings such as cancer, vascular restenosis, and immunological disorders. We investigated whether encapsulation of ganciclovir (GCV) into liposomes would improve its efficacy, especially against hepatic tumors. Large unilamellar liposomes containing GCV were prepared by reversed-phase evaporation. Pharmacokinetic studies in rats showed that, compared with free GCV, the intravenous injection of liposome-encapsulated GCV (lip-GCV) led to a faster decrease in GCV plasma concentrations, but higher liver-blood ratios. After treatment of syngeneic HSV-1 TK+ liver metastases in rats, histologically active tumors were found in 95% of the transplanted lesions when physiological saline had been given and in 50% when free GCV had been given at 90.2 microM/kg twice daily. This dose is known to be insufficient for the eradication of HSV-1 TK+ tumors. In contrast, only 5% viable tumors were found in rats receiving lip-GCV at this same concentration. Average tumor volumes were 19 +/- 15, 7 +/- 9, and <1 mm3 for the control, free GCV, and lip-GCV groups, respectively. GCV-related toxicity was no longer observed. The results demonstrate that liposomal encapsulation of GCV is feasible and significantly enhances its efficacy against HSV-1 TK+ hepatic tumors.

A Pharmacokinetic-Pharmacodynamic Model for Predicting the Impact of CYP2C9 and VKORC1 Polymorphisms on Fluindione and Acenocoumarol During Induction Therapy

Background and ObjectiveVitamin K epoxide reductase complex, subunit 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) polymorphisms are taken into account when predicting a safe oral dose of coumarin anticoagulant therapy, but little is known about the effects of genetic predictors on the response to fluindione and acenocoumarol. The aims of this study were to characterize the relationship between fluindione and acenocoumarol concentrations and the international normalized ratio (INR) response, and to identify genetic predictors that are important for dose individualization.MethodsFluindione concentrations, S- and R-acenocoumarol concentrations, the INR and genotype data from healthy subjects were used to develop a population pharmacokinetic-pharmacodynamic model in Monolix software. Twenty-four White healthy subjects were enrolled in the pharmacogenetic study. The study was an open-label, randomized, two-period cross-over study. The subjects received two doses of an oral anticoagulant: 20 mg of fluindione (period A) or 4 mg of acenocoumarol (period B). The pharmacokinetics and pharmacodynamics were studied from day 2 to day 3.ResultsA two-compartment model with a first-order input model was selected as the base model for the two drugs. The pharmacodynamic response was best described by an indirect action model with S-acenocoumarol concentrations and fluindione concentrations as the only exposure predictors of the INR response. Three covariates (CYP2C9 genotype, VKORC1 genotype and body weight) were identified as important predictors for the pharmacokinetic-pharmacodynamic model of S-acenocoumarol, and four covariates (CYP2C9 genotype, VKORC1 genotype, CYP1A2 phenotype and body weight) were identified as predictors for the pharmacokinetic-pharmacodynamic model of fluindione. Because some previous studies have shown a dose-response relationship between smoking exposure and the CYP1A2 phenotype, it was also noted that smokers have greater CYP1A2 activity.ConclusionDuring initiation of therapy, CYP2C9 and VKORC1 genetic polymorphisms are important predictors of fluindione and acenocoumarol pharmacokinetic-pharmacodynamic responses. Our result suggests that it is important to take the CYP1A2 phenotype into account to improve individualization of fluindione therapy, in addition to genetic factors.

High variability of indinavir and nelfinavir pharmacokinetics in HIV-infected patients with a sustained virological response on highly active antiretroviral therapy.

ObjectivesTo describe plasma concentrations of indinavir alone or combined with ritonavir, and of nelfinavir and its active metabolite M8, and to measure their variabilities in HIV-infected patients treated with a stable antiretroviral regimen and experiencing a sustained virological response for at least 12 months.Patients and methodsIn this prospective trial, blood samples were drawn during a 6-hour time interval between two doses at enrolment to assess protease inhibitor (PI) pharmacokinetic parameters, and 4 months later to assess plasma trough and peak concentrations. Safety and adherence assessments and laboratory data were collected during an 8-month period. PI pharmacokinetic characteristics were analysed using a non-compartmental approach. Inter- and intrapatient variabilities were estimated using a linear mixed-effect model. The impact of different covariates on plasma trough concentrations was investigated. Eighty-eight patients were analysed: 42 treated with indinavir and 46 with nelfinavir.ResultsThe interquartile range (IQR) of the plasma trough concentration corrected for the sampling time (Ccalc) was 116–374 μg/L for indinavir alone and 163–508 μg/L for indinavir/ritonavir. Ritonavir significantly increased indinavir elimination half-life and plasma exposure. For nelfinavir, the IQR of Ccalc was 896–2059 μg/L for three-times-daily administration and 998–2124 μg/L for twice-daily administration. Variabilities were high for both PIs. Intrapatient variability for indinavir alone (and indinavir + ritonavir) was 76% (107%) and interpatient variability was 58% (10%) in adherent patients. Intrapatient variability for nelfinavir three times daily (and twice daily) was 41% (74%) and interpatient variability was 62% (50%). Intrapatient variability was lowered in patients with a high adherence level.ConclusionAlthough performed in a homogeneous population, this study documented a high interpatient but also intrapatient variability of indinavir and nelfinavir pharmacokinetics, which should be taken into account when interpreting therapeutic drug monitoring. Once patients have reached a sustained virological response, plasma PI monitoring may have a limited impact.

Modeling INR data to predict maintenance fluindione dosage

This study was designed to construct a pharmacokinetic/pharmacodynamic model describing the evolution of International Normalized Ratio (INR) under oral anticoagulation treatment by fluindione in patients and to develop a method for individualization of fluindione dosage. Three indirect response models describing the concentration-INR relationship were tested using a nonparametric estimation method. INR was modelled as a quantity being produced and eliminated. According to a log-likelihood ratio test, the evolution of INR was best modelled as an inhibition of its elimination by fluindione. The selected model was evaluated in 24 additional patients with INR measurements (after 2, 3, 4, 6, and 10 doses). Using a Bayesian method with data until day 4, INR was correctly predicted for days 6 and 10. The population characteristics of fluindione were estimated, pooling the two groups of patients. A Bayesian method for individualization of dosage regimen was developed, based on a risk function for INR at steady state. Prescription rules for fluindione were derived using this method retrospectively on the 73 patients in this study.