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R Farinotti

Publications and source records attributed to R Farinotti.

At least 19 recordsLinked to original sources
PubMed2001

Determination of N-acetylation phenotype using caffeine as a metabolic probe and high-performance liquid chromatography with either ultraviolet detection or electrospray mass spectrometry.

A rapid, sensitive method using liquid chromatography-electrospray mass spectrometry (LC-ES-MS) was developed and evaluated for the simultaneous quantitative determination of caffeine metabolites 1U, 1X and AAMU in human urine. This method involved a simple dilution of urine samples. The chromatographic separation was achieved on a C18 reversed-phase column using a gradient of acetonitrile in 2 mM, pH 3.0 ammonium formate as mobile phase. After ionisation in an electrospray source, mass spectrometric detection was performed in the negative ion, selected ion monitoring mode. This method yielded acceptable accuracy and precision within the range 0.25-50 microg/ml. This analytical method was applied to investigate the N-acetylator phenotype of HIV-infected patients and compared with high-performance liquid chromatography with UV detection. Its specificity was better, which appeared to be absolutely necessary to prevent errors in metabolic ratios and phenotype interpretation.

Acetylation↗
PubMed2001

Intestinal absorption and metabolism of chlorpheniramine enantiomers in rat.

Chlorpheniramine (CPAM) is a chiral antihistaminic drug commercialized as a racemic mixture. The intestinal absorption and metabolism of CPAM have been investigated in rat using in vivo (oral and IV administration), in situ (intestinal loop model), and in vitro (everted sac model) experiments. Oral and IV administrations of 20 mg/kg of the racemic mixture show that the pharmacokinetics of CPAM are stereoselective, with higher AUCs for the (+)-S-enantiomer compared to its antipode. The monodesmethyl metabolite (DCPM) was quantifiable in blood and its pharmacokinetics are stereoselective after oral but not after IV administration. Experiments using intestinal loops and everted sacs showed that the absorption is not stereoselective and that in vivo stereoselective formation of DCPM is presumably due to stereoselective hepatic metabolism. Moreover, the in vitro and in situ absorption of CPAM are not modified by modulators of P-glycoprotein and cytochromes P450 (cyclosporin A, ketoconazole).

Animals↗
PubMed2001

Maternal-fetal transfer and amniotic fluid accumulation of lamivudine in human immunodeficiency virus-infected pregnant women.

OBJECTIVE: The purpose of this study was to investigate placental transfer and amniotic fluid concentrations of lamivudine in human immunodeficiency virus-infected women who received the agent during pregnancy. STUDY DESIGN: Mothers in the study were receiving antiretroviral therapy that included lamivudine in a clinical setting. Maternal blood, cord blood, and amniotic fluid samples were obtained simultaneously at the time of delivery from 57 mother-infant pairs. RESULTS: At a median of 8.5 hours after the last maternal oral 150-mg dose of lamivudine, median maternal and fetal plasma concentrations were 302 and 240 ng/mL, respectively. Individual maternal and fetal concentrations were strongly correlated (r2 = 0.36; P < 10(-4)), and their median ratio was about 1. The median concentration in the amniotic fluid was 5 times higher than that in maternal plasma (upper range of ratio, 133). CONCLUSION: Lamivudine appeared to cross the placenta by simple diffusion and is concentrated in the amniotic fluid. High amniotic fluid levels of lamivudine may carry both benefits and risks for the child.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Maternal-fetal transfer of saquinavir studied in the ex vivo placental perfusion model.

OBJECTIVE: This study was undertaken to determine the placental transfer of the human immunodeficiency virus protease inhibitor saquinavir. STUDY DESIGN: An ex vivo perfused human placental cotyledon model was used. Ten placental perfusion studies were performed, with concentrations of saquinavir in the maternal compartment ranging from 322 to 2197 ng/mL (within reference therapeutic ranges). Drug concentrations were determined by high-performance liquid chromatography. RESULTS: The mean (+/- SD) fetal transfer rate of saquinavir was 1.8% +/- 1.6%, and the mean (+/- SD) clearance index was 0.05 +/- 0.05. A mean (+/- SD) of 1.6% +/- 3.1% of the perfused saquinavir was retained by the cotyledon. The small amount of saquinavir that crossed the placenta corresponded to the fraction not bound to human serum albumin. CONCLUSION: The low rate of placental transfer of saquinavir suggests that use of this antiretroviral drug by pregnant women may not lead to significant exposure of the fetus.

Female↗
PubMed2001

Effect of chronic renal failure on the expression and function of rat intestinal P-glycoprotein in drug excretion.

BACKGROUND: In chronic renal failure, the renal excretion of certain drugs is dramatically reduced. To determine whether other routes of drug elimination, such as secretion through the intestinal barrier by intestinal P-glycoprotein can be altered, we compared P-glycoprotein activity, P-glycoprotein protein content, and P-glycoprotein mRNA levels in intestine of control and chronic renal failure rats. METHODS: Chronic renal failure was surgically induced in rats by partial (7/8) nephrectomy. After 5 weeks, intestinal transport of rhodamine 123, a P-glycoprotein substrate, was carried out using an in vitro model of everted gut sacs. P-glycoprotein protein content was quantified by enzyme-linked immunosorbent assay and P-glycoprotein mRNA expression was evaluated by semi-quantitative reverse transcriptase polymerase chain reaction. RESULTS: A decrease of intestinal rhodamine 123 transport was observed in chronic renal failure rats, pointing to an inhibition of P-glycoprotein activity. Transport was inhibited in both sham-operated rats and rats with chronic renal failure by verapamil and cyclosporin A, but relative inhibition vs baseline was less marked in chronic renal failure than in sham-operated rats. In contrast, no significant differences in levels of P-glycoprotein protein or mRNA were observed between the two groups. CONCLUSIONS: Intestinal secretion of rhodamine 123 is mainly mediated by P-glycoprotein. It was reduced in rats with chronic renal failure, reflecting reduced intestinal drug elimination via a decrease in P-glycoprotein transport activity rather than via protein underexpression.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

Interactions of racemic mefloquine and its enantiomers with P-glycoprotein in an immortalised rat brain capillary endothelial cell line, GPNT.

The brain distribution of the enantiomers of the antimalarial drug mefloquine is stereoselective according to the species. This stereoselectivity may be related to species-specific differences in the properties of some membrane-bound transport proteins, such as P-glycoprotein (P-gp). The interactions of racemic mefloquine and its individual enantiomers with the P-glycoprotein efflux transport system have been analysed in immortalised rat brain capillary endothelial GPNT cells. Parallel studies were carried out for comparison in human colon carcinoma Caco-2 cells. The cellular accumulation of the P-glycoprotein substrate, [(3)H]vinblastine, was significantly increased both in GPNT cells and in Caco-2 cells when treated with racemic mefloquine and the individual enantiomers. In GPNT cells, the (+)-stereoisomer of mefloquine was up to 8-fold more effective than its antipode in increasing cellular accumulation of [(3)H]vinblastine, while in Caco-2 cells, both enantiomers were equally effective. These results suggest that racemic mefloquine and its enantiomers are effective inhibitors of P-gp. Furthermore, a stereoselective P-glycoprotein inhibition is observed in rat cells but not in human cells. The efflux of [(14)C]mefloquine from GPNT cells was decreased when the cells were incubated with the P-gp modulators, verapamil, cyclosporin A or chlorpromazine, suggesting that MQ could be a P-gp substrate.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Stereospecific versus nonstereospecific assessments for the bioequivalence of two formulations of racemic chlorpheniramine.

Chlorpheniramine (chlorphenamine, CPAM) is a racemic antihistaminic H1 drug containing two enantiomers. The aim of this study was to assess the bioequivalence of two formulations (reference and Vietnamese-tested formulation) of racemic chlorpheniramine combined with phenylpropanolamine in an open-labeled, randomized, crossover two-period study, after administration of 8 mg of racemic chlorpheniramine in 12 healthy Vietnamese subjects. First, dissolution of both formulations was tested in vitro according to USP requirements. Then the 12 subjects received both formulations after an overnight fast and a 7-day wash-out period. Plasma samples were collected up to 168 h. Plasma concentrations of total chlorpheniramine and its individual enantiomers were determined with a validated chiral HPLC method and pharmacokinetic parameters were estimated using model-independent analysis. For the reference formulation, Cmax and AUC values were higher for (+)S-chlorpheniramine ((+)S-CPAM) compared to (-)R-chlorpheniramine ((-)R-CPAM) (13.3 vs. 6.8 ng/ml and 409 vs. 222 ng/ml/h, respectively) while Clt/F and Vd/F were lower (9.8 vs. 17.6 l/h and 321 vs. 627 l, respectively). No difference was observed for Tmax, t(1/2), and MRT. Pharmacokinetic parameters were similar for the reference and the Vietnamese-tested formulation. Bioequivalence was assessed by Schuirmann test, as recommended by the current FDA and European Community criteria. Dissolution tests showed that both formulations were equivalent. A nonstereospecific, but not a stereospecific, approach indicated bioequivalence between the formulations.

Adult↗
PubMed2000

In vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia.

We evaluated the in vivo activity of levofloxacin alone or in combination with imipenem or amikacin in a mouse model of Acinetobacter baumannii pneumonia using a susceptible strain and one with low-level resistance (MIC/MBC of levofloxacin: 0.06/0.06 and 4/4 mg/L, respectively). As demonstrated previously with other pathogens, the AUC/MIC ratio predicted the efficacy of fluoroquinolones against A. baumannii. This parameter correlated with bactericidal effect and survival. Combination therapy did not enhance the efficacy of levofloxacin.

Acinetobacter Infections↗
PubMed2000

Placental transfer of pyrimethamine studied in an ex vivo placental perfusion model.

Pyrimethamine is used as and anti-infectious agent because of its antifolate properties. Its action is synergistic with that of dapsone and sulfamides on Toxoplasma gondii. The goal of the present study was to evaluate the placental transfer of pyrimethamine in an ex vivo model of perfused human placental cotyledon at term. Human placentas were perfused according to the slightly modified method of Schneider. The pyrimethamine fetal transfer rate was approximately 30%, while cotyledon clearance was about 1.8 ml/min. The placental transfer of pyrimethamine seems to be independent of the maternal concentrations of pyrimethamine, suggesting passive diffusion mechanisms or a nonsaturable active transport at the tested concentrations.

Female↗
PubMed2000

alpha(2)-adrenergic receptors stimulate oligopeptide transport in a human intestinal cell line.

Di- and tripeptides, as well as peptidomimetic drugs such as cephalexin (CFX), are absorbed by enterocytes via the oligopeptide transporter PepT1. We recently showed that the alpha(2)-adrenergic agonist clonidine increases CFX absorption in anaesthetized rats. Herein, we investigated whether alpha(2)-adrenergic receptors can directly affect PepT1 activity in a clone of the differentiated human intestinal cell line Caco-2 (Caco-2 3B) engineered to stably express alpha(2A)-adrenergic receptors at a density similar to that found in normal mucosa. Measurement of CFX fluxes across cell monolayers cultured on transwell filters demonstrated that the alpha(2)-agonists clonidine and UK14304 caused a 2-fold increase of CFX transport in Caco-2 3B cells, but not in Caco-2 (expressing PepT1 but not alpha(2)-adrenergic receptors) or in the HT29 19A clone (expressing alpha(2)-adrenergic receptors but not PepT1). The stimulatory effect of clonidine was abolished by glycyl-sarcosine (a competitor for the transporter) and blocked by yohimbine or RX821002 (alpha(2)-antagonists). Analysis of the kinetics of CFX transport in control and clonidine-treated Caco-2 3B cells showed that clonidine increased V(max) of CFX transport without changing K(m). Clonidine action was abolished by colchicine but not altered by amiloride, demonstrating that microtubule integrity but not Na(+)/H(+) exchanger activity is necessary for the effect of alpha(2)-agonists to occur. In conclusion, clonidine can directly activate alpha(2)-adrenergic receptors located on epithelial cells. The precise molecular mechanisms whereby these receptors modulate PepT1 activity remain to be elucidated but an increased translocation to the apical membrane of preformed cytoplasmic transporter molecules is likely to be involved.

Adrenergic alpha-2 Receptor Agonists↗
PubMed2000

Chronic nifedipine dosing enhances cephalexin bioavailability and intestinal absorption in conscious rats.

Cephalexin, a beta-lactam antibiotic, is rapidly absorbed via the di-and tripeptide intestinal transporters, as for many peptidomimetic drugs. Acute nifedipine has been shown to increase intestinal absorption of several beta-lactams: amoxicillin and cefixime in humans, and cephalexin in the rat. We showed previously that the nervous system was involved in the increasing effect of nifedipine on cephalexin intestinal absorption in anesthetized rats. The aim of the present study was 2-fold: 1) to investigate whether the effect of nifedipine is maintained in conscious rats, and 2) to determine whether the nifedipine effect will persist during chronic nifedipine administration. Acute and chronic oral administration of nifedipine significantly increased oral cephalexin area under the plasma concentration-time curve (34 and 25%, respectively) and maximum concentration in plasma (57 and 51%, respectively), while the distribution and elimination parameters of intra-arterial cephalexin were not affected by acute or chronic nifedipine administration. In conclusion, acute nifedipine effect on intestinal absorption of cephalexin is independent of anesthesia in rats. Since nifedipine could still enhance cephalexin intestinal absorption after a 7-day b.i.d. treatment, it can be envisaged to apply this effect to increase bioavailability of poorly absorbed peptidomimetic drugs in man.

Animals↗
PubMed1999

Determination of nelfinavir, a potent HIV protease inhibitor, and its active metabolite M8 in human plasma by high-performance liquid chromatography with photodiode-array detection.

We developed and characterized a high-performance liquid chromatographic assay for the determination of nelfinavir (NFV), a potent HIV protease inhibitor, and its active metabolite M8 in human plasma. Extraction of the internal standard, M8 and NFV from the plasma buffered at pH 9.5 was achieved by a liquid-liquid extraction with a mixture of methyl-tert.-butyl ether and hexane. Following two washes of the reconstituted sample with hexane, separation was achieved on an octadecylsilyl analytical column with a mobile phase containing 0.1% trifluoroacetic acid-acetonitrile-methanol (51:46:5, v/v). Detection was performed using an ultraviolet photodiode-array detector. The signal was monitored at a wavelength of 220 nm. The assay was found to be linear and has been validated over the concentration range of 25 to 3000 microg/l for M8 and 25 to 6000 microg/l for NFV, from 500 microl of plasma. Recoveries were 98.9% (SD 8.9%), and 100.2% (SD 11.7%) for M8 and NFV, respectively. Concentrations that gave a signal-to-noise ratio of three (15 microg/l for both M8 and NFV) were selected to determine the limit of detection. The lower limit of quantification (25 microg/l for both M8 and NFV) was defined as the concentration for which the relative standard deviation and the percent deviation from the nominal concentration were lower than 20%.

Anti-HIV Agents↗
PubMed1999

Drug interactions with diosmectite: a study using the artificial stomach-duodenum model.

Drug interactions with diosmectite, a gastric-protective drug, were studied in vitro using an artificial stomach-duodenum model. The behavior of neutral and ionisable drugs with pKa values ranging between 2 and 8 was monitored to determine the physicochemical characteristics of the interactions. The main neutral (digoxin) and acid (valproic acid) drug substances were moderately fixed by clay (<27%), in a pH-independent manner. Basic compounds with a pKa<7 (dapsone, metronidazole, cimetidine) were strongly fixed in acid medium (?62%), and fully released under neutral conditions. Amphoteric (fluoroquinolones) and basic compounds with a pKa>/=7 (ranitidine, pyrimethamine) were adsorbed by more than 81% by diosmectite in gastric and duodenal compartments. In the part of the model representing the distal duodenum, the potential site for drug absorption, only the active substances which remained positively charged (amphoteric and basic compounds) showed a large reduction (>/=80%) in their available free fraction. Ionisation of drug substances administered per os concomitantly with diosmectite plays a crucial role in these interactions.

Adsorption↗
PubMed1999

Cerium-doped diosmectite for topical application studies of the cerium-clay interaction.

Cerium is used for its antiseptic and immunomodulatory properties in burn injury. We have developed a cerium-doped clay to replace existing ointments. Adsorption and release of cerium (Ce3+) by diosmectite were studied at 22+/-2 degrees C, in the presence of various other cationic species. Simple spectrofluorimetric determination of cerium was used (lambdaexc=240 nm/lambdaem=360 nm). Cerium binding reached a plateau within 2 min and was a function of the electrolyte content of the solution in contact with the clay. Langmuir isotherm treatment led to a maximal binding capacity of 66 mg of Ce3+ per gram of clay. Partial release occurred within 2 min (19% in the presence of isotonic NaCl solution). The ionic strength of the solution, and the ionic radius and charge of the electrolytes present in the bathing solution significantly influenced cerium release, in contrast to pH and temperature changes. These results strongly point to a cationic exchange mechanism between diosmectite and cerium solution.

Administration, Topical↗
PubMed1999

Stereoselective binding of zopiclone to human plasma proteins.

The binding of racemic zopiclone (ZOP) and of its two enantiomers to plasma proteins, albumin and alpha 1-acid glycoprotein were compared. Our work shows that the binding of ZOP to human plasma proteins is stereoselective. The total plasma protein binding percentages were 79.3 +/- 5.5%, 83.8 +/- 5.2%, and 75.1 +/- 2.1%, for racemic zopiclone, (-)zopiclone and (+)zopiclone, respectively. These results were confirmed by the analysis of samples obtained from healthy volunteers after the oral administration of ZOP. The anticoagulant used for sampling was also shown to have an influence on the percentage binding and on its stereoselectivity. Considering albumin and alpha 1-acid glycoprotein separately, stereoselectivity was also observed.

Azabicyclo Compounds↗
PubMed1999

Binding of chlorpheniramine enantiomers to human plasma proteins.

The in vitro binding of RS-chlorpheniramine to human proteins was studied by equilibrium dialysis. The binding to total plasma proteins and to individual albumin and alpha-glycoprotein acid is stereoselective. (+)S-chlorpheniramine is more extensively bound than its antipode to total plasma proteins (38% vs. 23%), to albumin (20% vs. 15%) and to alpha-glycoprotein acid (23% vs. 5%).

Blood Proteins↗
PubMed1999

Active intestinal elimination of ciprofloxacin in rats: modulation by different substrates.

1. Two in vivo models, in the rat, were used to investigate, in the presence of different substrates, the overall and net intestinal elimination of ciprofloxacin: an open-intestinal perfusion model and an intestinal loop model respectively. 2. In the presence of quinidine, verapamil and cyclosporin (substrates of the P-glycoprotein (P-gp)), plasma AUCs of ciprofloxacin were 1.5 - 2 fold increased, while biliary clearance (1.5 - 2 fold), intestinal overall and net clearances (2 - 4 fold and 1.5 - 8 fold respectively) decreased. The weak effect obtained with cyclosporin as compared to verapamil and especially quinidine, suggests, for ciprofloxacin, the existence of transport systems distinct from the P-gp, as the OCT1 transporter which could be inhibited by quinidine. 3. With cephalexin and azlocillin, two beta-lactam antibiotics, plasma AUCs of ciprofloxacin increased and biliary and intestinal overall clearances decreased in a similar fashion (1.3 - 2 fold), suggesting the involvement of organic anion and/or cation transporters. 4. In the presence of structural analogues, the effect was dependent on the compound administered: Sparfloxacin had no effect on intestinal clearance of ciprofloxacin. In contrast, with pefloxacin, overall intestinal clearance of ciprofloxacin was decreased and net intestinal clearance increased. 5. The specificity of ciprofloxacin intestinal transport appears to be different from P-gp as outlined by the lack of competition with sparfloxacin, a P-gp substrate. Ciprofloxacin intestinal elimination seems to be mediated by organic anion and/or cation transporters and a mechanism sensitive to quinidine and verapamil.

Animals↗