Improved intestinal absorption of sulpiride in rats with synchronized oral delivery systems

Monophasic coamorphous sulpiride: a leap in physicochemical attributes and dual inhibition of GlyT1 and P-glycoprotein, supported by experimental and computational insights

Study aimed to design and development of a supramolecular formulation of sulpiride (SUL) to enhance its solubility, dissolution and permeability by targeting a novel GlyT1 inhibition mechanism. SUL is commonly used to treat gastric and duodenal ulcers, migraine, anti-emetic, anti-depressive and anti-dyspeptic conditions. Additionally, Naringin (NARI) was incorporated as a co-former to enhance the drug's intestinal permeability by targeting P-glycoprotein (P-gp) efflux inhibition. NARI, a flavonoid has diverse biological activities, including anti-apoptotic, anti-oxidant, and anti-inflammatory properties. This study aims to design and develop a supramolecular formulation of SUL with NARI to enhance its solubility, dissolution, and permeability by targeting a novel GlyT1 inhibition mechanism, extensive experimental characterization was performed using solid-state experimental techniques in conjunction with a computational approach. This approach included quantum mechanics-based molecular dynamics (MD) simulation and density functional theory (DFT) studies to investigate intermolecular interactions, phase transformation and various electronic structure-based properties. The findings of the miscibility study, radial distribution function (RDF) analysis, quantitative simulations of hydrogen/π-π bond interactions and geometry optimization aided in comprehending the coamorphization aspects of SUL-NARI Supramolecular systems. Molecular docking and MD simulation were performed for detailed binding affinity assessment and target validation. The solubility, dissolution and ex-vivo permeability studies demonstrated significant improvements with 31.88-fold, 9.13-fold and 1.83-fold increments, respectively. Furthermore, biological assessments revealed superior neuroprotective effects in the SUL-NARI coamorphous system compared to pure SUL. In conclusion, this study highlights the advantages of a drug-nutraceutical supramolecular formulation for improving the solubility and permeability of SUL, targeting novel schizophrenia treatment approaches through combined computational and experimental analyses.

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: Focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialised tools are used. Three tools have been proven useful to personalise drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimise treatment effects, minimise side effects and ultimately reduce the global burden of diseases, personalised drug treatment has not yet become the standard of care in psychiatry.

Intranasal delivery of sulpiride nanostructured lipid carrier to central nervous system; in vitro characterization and in vivo study

The low and erratic oral absorption of sulpiride (SUL) a dopaminergic receptor antagonist, and its P-glycoprotein efflux in the gastrointestinal tract restricted its oral route for central nervous system disorders. An intranasal formulation was formulated based on nanostructured lipid carrier to tackle these obstacles and deliver SUL directly to the brain. Sulipride-loaded nanostructured lipid carrier (SUL-NLC) was prepared using compritol®888 ATO and different types of liquid lipids and emulsifiers. SUL-NLCs were characterized for their particle size, charge, and encapsulation efficiency. Morphology and compatibility with other NLC excipients were also studied. Moreover, SUL in vitro release, nanodispersion stability, in vivo performance and SUL pharmacokinetics were investigated. Results delineates that SUL-NLC have a particle size ranging from 366.2 ± 62.1 to 640.4 ± 50.2 nm and encapsulation efficiency of 75.5 ± 1.5%. SUL showed a sustained release pattern over 24 h and maintained its physical stability for three months. Intranasal SUL-NLC showed a significantly (p < 0.01) higher SUL brain concentration than that found in plasma after oral administration of commercial SUL product with 4.47-fold increase in the relative bioavailability. SUL-NLCs as a nose to brain approach is a promising formulation for enhancing the SUL bioavailability and efficient management of neurological disorders.

The Exploitation of Sodium Deoxycholate-Stabilized Nano-Vesicular Gel for Ameliorating the Antipsychotic Efficiency of Sulpiride

The present study explored the effectiveness of bile-salt-based nano-vesicular carriers (bilosomes) for delivering anti-psychotic medication, Sulpiride (Su), via the skin. A response surface methodology (RSM), using a 33 Box-Behnken design (BBD) in particular, was employed to develop and optimize drug-loaded bilosomal vesicles. The optimized bilosomes were assessed based on their vesicle size, entrapment efficiency (% EE), and the amount of Sulpiride released. The Sulpiride-loaded bilosomal gel was generated by incorporating the optimized Su-BLs into a hydroxypropyl methylcellulose polymer. The obtained gel was examined for its physical properties, ex vivo permeability, and in vivo pharmacokinetic performance. The optimum Su-BLs exhibited a vesicle size of 211.26 ± 10.84 nm, an encapsulation efficiency of 80.08 ± 1.88% and a drug loading capacity of 26.69 ± 0.63%. Furthermore, the use of bilosomal vesicles effectively prolonged the release of Su over a period of twelve hours. In addition, the bilosomal gel loaded with Su exhibited a three-fold increase in the rate at which Su transferred through the skin, in comparison to oral-free Sulpiride. The relative bioavailability of Su-BL gel was almost four times as high as that of the plain Su suspension and approximately two times as high as that of the Su gel. Overall, bilosomes could potentially serve as an effective technique for delivering drugs through the skin, specifically enhancing the anti-psychotic effects of Sulpiride by increasing its ability to penetrate the skin and its systemic bioavailability, with few adverse effects.

Enhancing the Low Oral Bioavailability of Sulpiride via Fast Orally Disintegrating Tablets: Formulation, Optimization and In Vivo Characterization

Sulpiride (SUL) is a dopamine D₂-receptor antagonist used for management of GIT disturbance and it has anti-psychotic activities based on the administered dose. SUL undergoes P-glycoprotein efflux, which lead to poor bioavailability and erratic absorption. Therefore, the objective of this research was an attempt to enhance the oral bioavailability of SUL via formulation of fast disintegrating tablets (SUL-FDTs) with a rapid onset of action. A 3² full-factorial design was performed for optimization of SUL-FDTs using desirability function. The concentration of superdisintegrant (X₁) and Prosolv^® (X₂) were selected as independent formulation variables for the preparation and optimization of SUL-FDTs using direct compression technique. The prepared SUL-FDTs were investigated regarding their mechanical strength, disintegration time, drug release and in vivo pharmacokinetic analysis in rabbits. The optimized formulation has hardness of 4.58 ± 0.52 KP, friability of 0.73 ± 0.158%, disintegration time of 37.5 ± 1.87 s and drug release of 100.51 ± 1.34% after 30 min. In addition, the optimized SUL-FDTs showed a significant (p < 0.01) increase in C_max and AUC(_0-∞) and a relative bioavailability of about 9.3 fold compared to the commercial product. It could be concluded that SUL-FDTs are a promising formulation for enhancing the oral bioavailability of SUL concomitant with a fast action.

Synchronizing the release rates of salicylate and indomethacin from degradable chitosan hydrogel and its optimization by definitive screening design

Three types of ionically crosslinked (with citric acid) chitosan discs were loaded with the highly water- soluble drug, sodium salicylate (SS) and the poorly water-soluble drug, indomethacin (Ind). In separate experiments the hydrated discs were immersed in a de-crosslinking solution comprising of different concentrations of calcium chloride, which induced a controlled erosion of the discs, a process which was optimized to synchronize the release rates of the two drugs over a predetermined period of time. The optimization was accomplished by manipulating six factors: chitosan MW, its amount in the formulation, the concentration of the crosslinker agent, the concentration of the de-crosslinking agent in the dissolution medium, its pH and its temperature. A computerized multifactorial definitive screening design analysis assisted in minimizing the number of experiments. The quotient of the SS to Ind release rates, the difference factor f1, the similarity factor f2 and the combination of f1 and f2 were determined as the experimental responses. The computerized prediction profilers that were used to simulate the contribution of the experimental factors and their effect on the experimental responses led to a successful erodible formulation with a concomitant release of the two drugs over 150 min.

Outlook on the Application of Metal-Liganded Bioactives for Stimuli-Responsive Release

Direct metal-liganded bioactive coordination complexes are known to be sensitive to stimuli such as pH, light, ion activation, or redox cues. This results in the controlled release of the bioactive(s). Compared to other drug delivery strategies based on metal complexation, this type of coordination negates a multi-step drug loading methodology and offers customized physiochemical properties through judicious choice of modulating ancillary ligands. Bioactive release depends on simple dissociative kinetics. Nonetheless, there are challenges encountered when translating the pure coordination chemistry into the biological and physiological landscape. The stability of the metal-bioactive complex in the biological milieu may be compromised, disrupting the stimuli-responsive release mechanism, with premature release of the bioactive. Research has therefore progressed to the incorporation of metal-liganded bioactives with established drug delivery strategies to overcome these limitations. This review will highlight and critically assess current research interventions in order to predict the direction that pharmaceutical scientists could pursue to arrive at tailored and effective metal-liganded bioactive carriers for stimuli-responsive drug release.

Comparison of solvent-wetted and kneaded l-sulpiride-loaded solid dispersions: Powder characterization and in vivo evaluation

The purpose of this study was to compare the powder properties, solubility, dissolution and oral absorption of solvent-wetted (SWSD) and kneaded (KNSD) l-sulpiride-loaded solid dispersions. The SWSD and KNSD were prepared with silicon dioxide, sodium laurylsulfate and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) using a spray dryer and high shear mixer, respectively. Their powder properties, solubility, dissolution and oral absorption were assessed compared to l-sulpiride powder. The drug in SWSD was in the amorphous state; however, in KNSD, it existed in the crystalline state. The SWSD with a drug/sodium laurylsulphate/TPGS/silicon dioxide ratio of 5/1/2/12 gave the higher drug solubility and dissolution compared to the KNSD with the same composition. The oral absorption of drug in the SWSD was 1.4 fold higher than the KNSD and 3.0 fold higher than the l-sulpiride powder (p<0.05) owing to better solubility and reduced crystallinity. Furthermore, the SWSD at the half dose was bioequivalent of commercial l-sulpiride-loaded product in rats. Thus, the SWSD with more improved oral absorption would be recommended as an alternative for the l-sulpiride-loaded oral administration.

Novel sulpiride-loaded solid lipid nanoparticles with enhanced intestinal permeability

Background

Solid lipid nanoparticles (SLN), novel drug delivery carriers, can be utilized in enhancing both intestinal permeability and dissolution of poorly absorbed drugs. The aim of this work was to enhance the intestinal permeability of sulpiride by loading into SLN.

Methods

A unique ultrasonic melt-emulsification method with minimum stress conditions was used for the preparation of SLN. The mixture of the drug and the melted lipids was simply dispersed in an aqueous solution of a surfactant at a temperature that was 10°C higher than the melting points of the lipids using probe sonication, and was then simultaneously dispersed in cold water. Several formulation parameters were optimized, including the drug-to-lipid ratio, and the types of lipids and surfactants used. The produced SLN were evaluated for their particle size and shape, surface charge, entrapment efficiency, crystallinity of the drug and lipids, and the drug release profile. The rat everted sac intestine model was utilized to evaluate the change in intestinal permeability of sulpiride by loading into SLN.

Results

The method adopted allowed successful preparation of SLN with a monodispersed particle size of 147.8–298.8 nm. Both scanning electron microscopic and atomic force microscopic images showed uniform spherical particles and confirmed the sizes determined by the light scattering technique. Combination of triglycerides with stearic acid resulted in a marked increase in zeta potential, entrapment efficiency, and drug loading; however, the particle size was increased. The type of surfactant used was critical for particle size, charge, drug loading, and entrapment efficiency. Generally, the in vitro release profile demonstrated by all formulations showed the common biphasic mode with a varying degree of burst release. The everted sac model showed markedly enhanced sulpiride permeability in the case of the SLN-loaded formulation. The in situ results showed a very good correlation with the in vitro release data.

Conclusion

Incorporation of sulpiride into SLN results in enhanced intestinal permeability of sulpiride, that may in turn increase overall oral absorption of the drug. The superior attributes of the prepared SLN, specifically the high particle size uniformity and drug loading capacity, is considered novel, especially given the simplicity and modest nature of the sonication method used.

Effect of hydroxypropyl methyl cellulose phthalate coating on digestive stability and intestinal transport of green tea catechins

BACKGROUND

The purpose of this study was to investigate the effect of hydroxypropyl methyl cellulose phthalate (HPMCP) coating on the digestive stability and intestinal transport of green tea catechins (GTCs).

METHODS

Two types of HPMCP coating were prepared: one type with size smaller than 500 μm (S-HPMCP) and the other with size larger than 500 μm (L-HPMCP). An in vitro gastrointestinal model system coupled with Caco-2 cells was used for estimating the bioavailability of GTCs. Ultraperformance liquid chromatography with a photodiode array detector was performed to analyze GTCs.

RESULTS

The digestive stability of GTCs was enhanced up to 33.73% and 35.28% for S-HPMCP and L-HPMCP, respectively. Intestinal transport of the GTCs was increased to 22.98% and 23.23% for S-HPMCP and L-HPMCP, respectively. Overall, the bioavailability of GTCs increased by 4.08 and 11.71 times for S-HPMCP and L-HPMCP, respectively.

CONCLUSION

The results of this study confirm that coating with HPMCP could be a way to improve the digestive stability and intestinal transport of GTCs.

Therapeutic drug monitoring and pharmacokinetic compartmental analysis of sulpiride double-peak absorption profile after oral administration to human volunteers

BACKGROUND

The pharmacokinetics of oral drugs that exhibit double peaks cannot be described adequately by using conventional compartmental models.

OBJECTIVE

The aim of this study was to describe the double-peak plasma pharmacokinetic profile of sulpiride after oral administration to healthy volunteers based on physiological and biopharmaceutical considerations.

METHODS

A single 100 mg dose of sulpiride was given to 16 healthy volunteers. Blood samples were drawn at different times and analysed by a validated HPLC assay method. Plasma profiles were evaluated by non-compartmental and compartmental approaches.

RESULTS

The non-compartmental parameters determined were k (0.079±0.008 h(-1)), t1/2 (9.0±2.9 h), Vd /F (330.5±87.3 L), Cl/F (38.2±9.8 L/h) and AUC0→∞ (1402.5±404.7 ng.h/mL). The compartmental analysis was described appropriately using a two-compartment body model, with first order absorption from two different sites in the gut. The parameters determined were k21 (0.68±0.2 h(-1)), ka1 (0.7±0.27 h(-1)), ka2 (2.7±1.8 h(-1)) Vc/F (45.1±15.7 L), α (33.3±1.5 h(-1)), β (0.11±0.03 h(-1)) and time for the beginning of the absorption from the second site (4.4±2.1 h).

CONCLUSION

The developed analytical method was suitable for use in pharmacokinetic studies and therapeutic drug monitoring implementation. Sulpiride was well tolerated by the patients without any serious adverse events being observed. The double peaks in the serum concentration-time profiles could be due to differential rates of absorption along the gastrointestinal tract. The discontinuous absorption model with two sites of absorption was adequate to describe the double-peak of the sulpiride plasma profile. ClinicalTrials. gov identifiers: NCT01777685.

Synchronized release of Doxil and Nutlin-3 by remote degradation of polysaccharide matrices and its possible use in the local treatment of colorectal cancer

A novel approach to the prevention of colorectal cancer (CRC) recurrence by the local, luminal application of the combined therapies: Nutlin-3 (NUT) and the liposomal preparation of doxorubicin, Doxil(*) (Doxil) is presented here. The two drug entities were loaded into calcium alginate beads, engineered to erode upon exposure to a de-crosslinking agent, to allow for the controlled, concomitant release of the two. The synchronized release-driven improved cytotoxicity of NUT and Doxil was tested in vitro in RKO (wild-type p53) and HT-29 (mutant p53) CRC cells, by measuring intracellular expression of p53, p21 and Mdm2, as well as monitoring cell proliferation and viable cell numbers. NUT treatment alone was identified to be cytotoxic exclusively towards RKO cells. However, coadministration of NUT enhanced Doxil's anti-proliferative effects and cell death induction in a synergistic manner in both cell types. It was also identified that combinatorial treatment in a wt p53 context affected the p53 pathway by elevating the expression of p53 and its target p21. The capability of the formulation to erode in the presence of a de-crosslinking agent was demonstrated in vivo in the cecum of the anesthetized rat using indomethacin as a poorly water-soluble PK probe.

Nanomedicine in GI

Recent advances in nanotechnology offer new hope for disease detection, prevention, and treatment. Nanomedicine is a rapidly evolving field wherein targeted therapeutic approaches using nanotechnology based on the pathophysiology of gastrointestinal diseases are being developed. Nanoparticle vectors capable of delivering drugs specifically and exclusively to regions of the gastrointestinal tract affected by disease for a prolonged period of time are likely to significantly reduce the side effects of existing otherwise effective treatments. This review aims at integrating various applications of the most recently developed nanomaterials that have tremendous potential for the detection and treatment of gastrointestinal diseases.

Influence of ABCB1 genetic polymorphisms on the pharmacokinetics of levosulpiride in healthy subjects

The purposes of this study were to clarify the involvement of P-glycoprotein in the absorption of levosulpiride in knockout mice that lack the Abcb1a/ 1b gene, and to evaluate the relationship between genetic polymorphisms in ABCB1 (exon 12, 21 and 26) and levosulpiride disposition in healthy subjects. The plasma and brain samples were obtained after oral administration (10 microg/g) of levosulpiride to abcb1a/1b(-/-) and wild-type mice (n=3 approximately 6 at each time point). The average brain-to-plasma concentration ratio and blood-brain barrier partitioning of levosulpiride were 2.3- and 2.0-fold higher in Abcb1a/1b(-/-) mice than in wild-type mice, respectively. A total of 58 healthy Korean volunteers receiving a single oral dose of 25 mg levosulpiride participated in this study. The subjects were evaluated for polymorphisms of the ABCB1 exon 12 C1236T, exon 21 G2677A/T (Ala893Ser/Thr) and exon 26 C3435T using polymerase chain reaction restriction fragment length polymorphism. The PK parameters (AUC(0-4h), AUC(0-infinity) and C(max.)) of ABCB1 2677TT and 3435TT subjects were significantly higher than those of subjects with at least one wild-type allele (P<0.05). The results indicate that levosulpiride is a P-glycoprotein substrate in vivo, which is supported by the effects of SNPs 2677G>A/T in exon 21 and 3435C>T in exon 26 of ABCB1 on levosulpiride disposition.

Polymeric and Low Molecular Mass Efflux Pump Inhibitors for Oral Drug Delivery

Transmembrane located transporter proteins can be responsible for the low bioavailability of orally administered drugs. Drug delivery systems which can overcome this barrier caused by efflux pumps are therefore highly on demand. Within the current review, intestinal located efflux transporters, methods to identify efflux pump substrates and inhibitors as well as strategies to minimize efflux pump mediated transport of drugs are discussed. Methods include in silico screening, transport and accumulation studies and monitoring of the ATPase activity. An emphasis has been placed on efflux pump inhibitors including low molecular mass inhibitors such as cyclosporine, PSC833 or KR30031 and polymeric inhibitors such as myrj, thiomers and cremophor EL. Also formulation approaches to circumvent intestinal segments with high efflux pump expression are briefly addressed.

Canine versus in vitro data for predicting input profiles of L-sulpiride after oral administration

The objective of this study was to assess the relative usefulness of canine versus in vitro data sets in the prediction of absorption of L-sulpiride (a low permeability compound) from an immediate and an extended release formulation. To reduce species differences on upper gastrointestinal residence times, human and canine data were collected in the fed state. In vitro permeability data (that were additionally confirmed by rat perfusion data) were obtained from the literature. In vitro release data were obtained in media simulating the gastric composition (without and with simultaneous protein digestion) and intestinal composition in the fed state. The results showed that, regardless of the formulation, canine input profiles were vastly different from human profiles at times longer than 2h after administration and led to 2.7 times higher total amount absorbed in dogs. In contrast, reliable in vitro permeability data in combination with in vitro release data collected in biorelevant media led to successful prediction of the human input profile; regardless of the dosage form, simulated and actual mean input profiles differed by less than 20%.

Novel methylcellulose-immobilized cation-exchange precolumn for on-line enrichment of cationic drugs in plasma

We developed a novel methylcellulose-immobilized strong cation-exchange (MC-SCX) precolumn for direct analysis of drugs in plasma. MC-SCX consists of silica gel with a methylcellulose outer-surface and a 2-(4-sulfophenyl) ethyl phase inner-surface. The MC-SCX precolumn was evaluated by direct analysis using pyridoxine, atenolol and sulpiride spiked in plasma, using a column-switching HPLC system. Each drug was retained and enriched on MC-SCX using an acidic mobile phase, which resulted in good linearity, sufficient reproducibility, intra- and inter day precision, and accuracy in analytical ion-pair LC with trifluoroacetic acid. The analytical methods for model drugs were applied to pharmacokinetics of atenolol and sulpiride in rats.

Impact of excipients on the absorption of P-glycoprotein substrates in vitro and in vivo

The efflux transporter, P-glycoprotein (P-gp), located in the apical membranes of intestinal absorptive cells, can reduce the bioavailability of a wide range of orally administered drugs. A number of surfactants/excipients have been shown to inhibit P-gp, and thus potentially enhance drug absorption. In this study, the improved everted gut sac technique was used to screen excipients for their ability to enhance the absorption of digoxin and celiprolol in vitro. The most effective excipients with digoxin were (at 0.5%, w/v): Labrasol > Imwitor 742 > Acconon E = Softigen 767 > Cremophor EL > Miglyol > Solutol HS 15 > Sucrose monolaurate > Polysorbate 20 > TPGS > Polysorbate 80. With celiprolol, Cremophor EL and Acconon E had no effect, but transport was enhanced by Softigen 767 > TPGS > Imwitor 742. In vivo, the excipients changed the pharmacokinetic profile of orally administered digoxin or celiprolol, but without increasing the overall AUC. The most consistent change was an early peak of absorption, probably due to the higher concentration of excipient in the proximal intestine where the expression of P-gp is lower. These studies show that many excipients/surfactants can modify the pharmacokinetics of orally administered drugs that are P-gp substrates.

Studies on Intestinal Absorption of Sulpiride (3): Intestinal Absorption of Sulpiride in Rats

The aim of this study was to investigate whether the concomitant administration of the substrates or inhibitors of PEPT1, OCTN1, OCTN2, and P-glycoprotein affects the intestinal absorption of sulpiride in rats. The absorption of sulpiride from rat intestine was decreased by the substrates or inhibitors of PEPT1, OCTN1, and OCTN2. On the other hand, the absorption was increased by the substrates of P-glycoprotein. The effects of these concomitantly administered drugs on the pharmacokinetic behavior of sulpiride after oral administration in rats were investigated. Peak concentration (C(max)) and area under the plasma concentration-time curve (AUC(0-8 h)) of sulpiride were decreased by the concomitant administration of the substrates or inhibitors of PEPT1, OCTN1, and OCTN2. However, the same parameters were significantly increased by the concomitant administration of the substrates of P-glycoprotein. The present results suggest the possibility of drug-drug interaction during the absorption process in the small intestine due to the coadministration of sulpiride and these agents. These findings provide important information for preventing adverse effects and for ensuring the effectiveness of sulpiride and concomitantly administered drugs.

How does the benzamide antipsychotic amisulpride get into the brain?--An in vitro approach comparing amisulpride with clozapine

This study evaluated the disposition of the two atypical antipsychotics, amisulpride (AMS) and clozapine (CLZ), and its main metabolite N-desmethylclozapine (DCLZ), to their target structures in the central nervous system by applying an in vitro blood-brain barrier and blood-cerebrospinal fluid (CSF) barrier based on monolayers of porcine brain microvessel endothelial cells (PMEC) or porcine choroid plexus epithelial cells (PCEC). Permeation studies through PMEC- and PCEC-monolayers were conducted for 60 min at drug concentrations of 1, 5, 10, and 30 muM applied to the donor compartment. PMEC were almost impermeable for AMS (permeation coefficient, P<1 x 10(-7) cm/s) in the resorptive direction, whereas transport in the secretory direction was observed with a P (+/-SD) of 5.2+/-3.6 x 10(-6) cm/s. The resorptive P of CLZ and DCLZ were 2.3+/-1.2 x 10(-4) and 9.6+/-5.0 x 10(-5) cm/s, respectively. For the permeation across PCEC in the resorptive direction, a P of 1.7+/-2.5 x 10(-6) cm/s was found for AMS and a P of 1.6+/-0.9 x 10(-4) and 2.3+/-1.3 x 10(-5) cm/s was calculated for CLZ and DCLZ, respectively. Both, CLZ and DCLZ, could easily pass both barriers with about a five-fold higher permeation rate of CLZ at the PCEC. The permeation of AMS across the BBB was restricted partly due to an efflux transport. It is thus suggested that AMS reaches its target structures via transport across the blood-CSF barrier.

Studies on intestinal absorption of sulpiride (2): transepithelial transport of sulpiride across the human intestinal cell line Caco-2

To determine the transport mechanism of sulpiride in an in vitro model of the human intestine, we investigated the transepithelial transport of this agent in Caco-2 cells. The transepithelial transport and intracellular accumulation of sulpiride were measured using Caco-2 cell monolayers cultured on a permeable membrane. The transepithelial transport of sulpiride in Caco-2 cells showed temperature dependence, and the transport was enhanced at weakly acidic pH on the apical side. These results demonstrate that the transepithelial transport of sulpiride is carrier mediated. To identify the drug transporter species that take part in the transepithelial transport of sulpiride, we examined the effects with the addition and preloading with specific substrates and inhibitors of various drug transporters. The results obtained from these examinations indicated that the apical-to-basolateral transport of sulpiride is mediated by the peptide transporter PEPT1, organic cation transporters OCTN1 and OCTN2 on the apical membrane, and the basolateral peptide transporter on the basolateral membrane. The basolateral-to-apical transport is mediated by the basolateral peptide transporter and organic cation transporter OCT1 on the basolateral membrane and by P-glycoprotein on the apical membrane. A decrease in the absorption of sulpiride may occur in coadministration protocols involving PEPT1-, OCTN1-, and OCTN2-transported drugs. Coadministration using the P-glycoprotein-transported drugs, in contrast, may enhance the absorption of sulpiride.

Studies on intestinal absorption of sulpiride (1): carrier-mediated uptake of sulpiride in the human intestinal cell line Caco-2

We investigated whether the uptake of a specific antipsychotic agent, sulpiride, in Caco-2 cells is mediated by a carrier-mediated system. Caco-2 cell monolayers were cultured in plastic culture dishes and uptake and efflux studies were conducted. The determination of sulpiride was performed by HPLC. At 37 degrees C, sulpiride uptake in pH 6.0 was twice as much as in pH 7.4. At 4 degrees C, however, no significant difference was observed between pH 6.0 and 7.4. The uptake at 4 degrees C was markedly lower than that obtained at 37 degrees C. The subtraction of the uptake at 4 degrees C from the uptake at 37 degrees C indicated a saturable process, and the result of the Eadie-Hofstee plot analysis indicated that the uptake consists of two or more saturable components. The uptake was significantly inhibited by uncoupler, protonophore, amino acid modifying agent and proteinase. Sulpiride efflux was temperature-dependent and was significantly inhibited by uncoupler and amino acid modifying agent. These findings indicate that sulpiride uptake and efflux in Caco-2 cells are carrier-mediated. Furthermore, the uptake was significantly decreased by some substrates and inhibitors of peptide transporter, PEPT1, and organic cation transporters, OCTN1 and OCTN2, and was significantly increased by preloading with them. The uptake was also significantly increased by a typical substrate of P-glycoprotein. From these findings, we presumed that peptide transporter PEPT1 and organic cation transporters OCTN1 and OCTN2 are involved with this uptake. P-glycoprotein may also contribute to the efflux of sulpiride.