Determination of some antiemetic drugs through its native fluorescence or fluorescence quenching of cerrous ammonium sulphate

The manuscript describes two fluorimetric methods for the determination of some antiemetic drugs namely granisetron HCl, ondansetron HCl and tropisetron HCl, used in the management of nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy. Granisetron HCl solution exhibits a native fluorescence, which can be applied for its determination at 365 nm upon excitation at 305 nm. The method was applied for the determination of granisetron HCl in drug substance, drug product as well as in presence of its acid induced degradation products. The quantum yield was calculated. The second proposed method is based on measuring the quenching effect induced by ondansetron HCl or tropisetron HCl on the fluorescence intensity of cerrous ammonium sulphate at λ_em 348 nm upon excitation at 250 nm in acidic medium. The analysis of quenching data showed that quenching of cerrous ammonium sulphate induced by ondansetron HCl or tropisetron HCl is mainly through dynamic quenching. Various variables affecting fluorescence response were studied and optimized. The obtained results were found to be statistically agreed with those obtained from the official or reported ones. Moreover, the validity of the methods was assessed according to ICH guidelines.

Enhanced transdermal delivery of ondansetron using nanovesicular systems: Fabrication, characterization, optimization and ex-vivo permeation study-Box-Cox transformation practical example

This study aimed to formulate suitable nanovesicles (NVs) for transdermal delivery of Ondansetron. It also illustrated a practical example for the importance of Box-Cox transformation. A 2³ full factorial design was used to enable testing transfersomes, ethosomes, and transethosomes of Ondansetron simultaneously. The independent variables (IVs) studied were sodium taurocholate amount, ethanol volume in hydration medium and sonication time. The studied dependent variables (DVs) were: particle size (PS), zeta potential (ZP) and entrapment efficiency (EE). Polynomial equations were used to study the influence of IVs on each DV. Numerical multiple response optimization was applied to select an optimized formula (OF) with the goals of minimizing PS and maximizing ZP absolute value and EE. Box-Cox transformation was adopted to enable modeling PS raised to the power of 1.2 with an excellent prediction R² of 1.000. ZP and EE were adequately represented directly with prediction R² of 0.9549 and 0.9892 respectively. Response surface plots helped in explaining the influence of IVs on each DV. Two-sided 95% prediction interval test and percent deviation of actual values from predicted ones proved the validity of the elucidated models. The OF was a transfersomal formula with desirability of 0.866 and showed promising results in ex-vivo permeation study.

Stability of Alprazolam, Atropine Sulfate, Glutamine, Levofloxacin, Metoprolol Tartrate, Nitrofurantoin, Ondansetron Hydrochloride, Oxandrolone, Pregabaline, and Riboflavin in SyrSpend SF pH4 Oral Suspensions

The objective of this study was to evaluate the stability of 10 commonly used active pharmaceutical ingredients compounded in oral suspensions using an internationally used suspending vehicle (SyrSpend SF PH4): alprazolam 1.0 mg/mL, atropine sulfate 0.1 mg/mL, glutamine 250.0 mg/mL, levofloxacin 50.0 mg/mL, metoprolol tartrate 10.0 mg/mL, nitrofurantoin 2.0 mg/mL, ondansetron hydrochloride 0.8 mg/mL, oxandrolone 3.0 mg/mL, pregabaline 20.0 mg/mL, riboflavin 10.0 mg/mL. All suspensions were stored at both controlled refrigeration (2°C to 8°C) and controlled room temperature (20°C to 25°C). Stability was assessed by measuring the percent recovery at varying time points throughout a 90-day period. Active pharmaceutical ingredients quantification was performed by high-performance liquid chromatography via a stability-indicating method. Given the percentage of recovery of the active pharmaceutical ingredients within the suspensions, the beyond-use date of the final products (active pharmaceutical ingredients + vehicle) was at least 90 days for all suspensions with regard to both temperatures. This suggests that the vehicle is stable for compounding active pharmaceutical ingredients from different pharmacological classes.

Galanin-Mediated Behavioural Hyperalgesia from the Dorsomedial Nucleus of the Hypothalamus Involves Two Independent Descending Pronociceptive Pathways

Activation of the dorsomedial nucleus of the hypothalamus (DMH) by galanin (GAL) induces behavioural hyperalgesia. Since DMH neurones do not project directly to the spinal cord, we hypothesized that the medullary dorsal reticular nucleus (DRt), a pronociceptive region projecting to the spinal dorsal horn (SDH) and/or the serotoninergic raphe-spinal pathway acting on the spinal 5-HT3 receptor (5HT3R) could relay descending nociceptive facilitation induced by GAL in the DMH. Heat-evoked paw-withdrawal latency (PWL) and activity of SDH neurones were assessed in monoarthritic (ARTH) and control (SHAM) animals after pharmacological manipulations of the DMH, DRt and spinal cord. The results showed that GAL in the DMH and glutamate in the DRt lead to behavioural hyperalgesia in both SHAM and ARTH animals, which is accompanied particularly by an increase in heat-evoked responses of wide-dynamic range neurons, a group of nociceptive SDH neurones. Facilitation of pain behaviour induced by GAL in the DMH was reversed by lidocaine in the DRt and by ondansetron, a 5HT3R antagonist, in the spinal cord. However, the hyperalgesia induced by glutamate in the DRt was not blocked by spinal ondansetron. In addition, in ARTH but not SHAM animals PWL was increased after lidocaine in the DRt and ondansetron in the spinal cord. Our data demonstrate that GAL in the DMH activates two independent descending facilitatory pathways: (i) one relays in the DRt and (ii) the other one involves 5-HT neurones acting on spinal 5HT3Rs. In experimental ARTH, the tonic pain-facilitatory action is increased in both of these descending pathways.

Optimization and characterization of chitosan films for transdermal delivery of ondansetron

The aim of this study was to develop novel transdermal films of ondansetron HCl with high molecular weight chitosan as matrix polymer and 2-(2-ethoxy-ethoxy) ethanol (Transcutol®) as plasticizer. In this context, firstly the physicochemical properties of gels used to formulate transdermal films were characterized and, physicochemical properties and bioadhesiveness of the transdermal films prepared with chitosan gels were assessed. The impact of three different types of terpenes, namely limonene, nerolidol and eucalyptol on in vitro skin permeation of ondansetron from transdermal films were also examined. ATR-FTIR measurements were performed to investigate the effects of the chitosan film formulations on in vitro conformational order of stratum corneum intercellular lipids after 24 h permeation study. The results showed that the chitosan gels consisting of Transcutol® as plasticizer and terpenes as penetration enhancer may be used to prepare transdermal films of ondansetron due to the good mechanical properties and bioadhesiveness of the transdermal films. Eucalyptol (1%) showed higher permeation enhancer effect than the other terpenes and control. ATR-FTIR data confirmed that finding in which eucalyptol induced a blue shift in the both CH₂ asymmetric and symmetric absorbance peak positions indicating increased lipid fluidity of stratum corneum.

Exploring the binding mechanism of ondansetron hydrochloride to serum albumins: spectroscopic approach

The mechanism of interaction of ondansetron hydrochloride (OND) to serum albumins [bovine serum albumin (BSA) and human serum albumin (HSA)] was studied for the first time employing fluorimetric, circular dichroism, FTIR and UV-vis absorption techniques under the simulated physiological conditions. Fluorimetric results were utilized to investigate the binding and conformational characteristics of protein upon interaction with varying concentrations of the drug. Higher binding constant values revealed the strong interaction between the drug and protein while the number of binding sites close to unity indicated single class of binding site for OND in protein. Thermodynamic results revealed that both hydrogen bond and hydrophobic interactions played a major role in stabilizing drug-protein complex. Site marker competitive experiments indicated that the OND bound to albumins at subdomin II A (Sudlow's site I). Further, the binding distance between OND and serum albumin was calculated based on the Förster's theory of non-radioactive energy transfer and found to be 2.30 and 3.41 nm, respectively for OND-BSA and OND-HSA. The circular dichroism data revealed that the presence of OND decreased the α-helix content of serum albumins. 3D-fluorescence results also indicated the conformational changes in protein upon interaction with OND. Further, the effects of some cations have been investigated in the interaction of drug to protein.

Fabrication and optimization of fast disintegrating tablets employing interpolymeric chitosan-alginate complex and chitin as novel superdisintegrants

The objective of the present work was to optimize the formulation of fast disintegrating tablets (FDTs) of ondansetron HCl containing novel superdisintegrants, possessing sufficient mechanical strength and disintegration time comparable to those containing crospovidone or croscarmellose sodium. The FDTs were formulated using a novel superdisintegrant (chitosan-alginate (1:1) interpolymer complex and chitin) to achieve a sweet tasting disintegrating system. The results revealed that chitin (5-20%) increased the porosity and decreased the DT of tablets. At higher concentrations chitin maintained tablet porosity even at 5.5 kg crushing strength. Ondansetron HCl was found to antagonize the wicking action of glycine. Further, evaluation of the mechanism of disintegration revealed that glycine transported the aqueous medium to different parts of the tablets while the chitosan-alginate complex swelled up due to transfer of moisture from glycine. This phenomenon resulted in breakage of the tablet within seconds. For preparing optimized FDTs, the reduced model equations generated from Box-Behnken design (BBD) were solved after substituting the known disintegration time of FDTs containing superdisintegrants in the reduced model equations. The results suggested that excipient system under investigation not only improved the disintegration time but also made it possible to prepare FDTs with higher crushing strength as compared to tablets containing known superdisintegrants.

Sites of metabolic substitution: investigating metabolite structures utilising ion mobility and molecular modelling

Drug metabolism is an integral part of the drug development and drug discovery process. It is required to validate the toxicity of metabolites in support of safety testing and in particular provide information on the potential to form pharmacologically active or toxic metabolites. The current methodologies of choice for metabolite structural elucidation are liquid chromatography/tandem mass spectrometry (LC/MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. There are, in certain cases, examples of metabolites whose sites of metabolism cannot be unequivocally identified by MS/MS alone. Utilising commercially available molecular dynamics packages and known quantum chemistry basis sets, an ensemble of lowest energy structures were generated for a group of aromatic hydroxylated metabolites of the model compound ondansetron. Theoretical collision cross-sections were calculated for each structure. Travelling-wave ion mobility (IMS) measurements were also performed on the compounds, thus enabling experimentally derived collision cross-sections to be calculated. A comparison of the theoretical and experimentally derived collision cross-sections were utilised for the accurate assignment of isomeric drug metabolites. The UPLC/IMS-MS method, described herein, demonstrates the ability to measure reproducibly by ion mobility, metabolite structural isomers, which differ in collision cross-section, both theoretical and experimentally derived, by less than 1 Å(2). This application has the potential to supplement and/or complement current methods of metabolite structural characterisation.

Ondansetron: design and development of oral pharmaceutical suspensions

Ondansetron is a carbazol with antiemetic properties that acts as a competitive and selective antagonist for the 5 HT3 serotonin receptors. It is used primarily to control nausea and vomiting caused by cytotoxic chemotherapy and radiotherapy, as well as in postoperative vomiting in gynecological surgery. The main aim of this work was to obtain a stable, long-acting oral suspension of ondansetron. To prolong the action, latexes are used as transport vehicles, specifically we tested, Aquateric, which comprises mainly cellulose acetophthalate. We prepared a complex drug-polymer, and the release profile of ondansetron was evaluated at acid, basic and acid-basic pH. This complex is additioned to a vehicle with xanthan gum and sodium carboxymethylcellulose (CMCNa) as thickeners to retard as much as possible particle sedimentation and thus increase physical stability of the suspension. The results obtained for sediment volume and degree of flocculation suggest that xanthan gum provides the best results, with better organolepticcharacteristics, appearance, physical stability and easy redispersability.

The metabolism of the 5HT3antagonists ondansetron, alosetron and GR87442 I: A comparison ofin vitroandin vivometabolism andin vitroenzyme kinetics in rat, dog and human hepatocytes, microsomes and recombinant human enzymes

The metabolism of the structurally related 5HT3 antagonists ondansetron, alosetron and GR87442 in the rat, dog and human was determined in hepatocytes, liver microsomes and human recombinant microsomes. The profiles of phase I metabolites were similar in human hepatocytes and microsomes. The metabolites of all three compounds produced in rat, dog and human microsomes and hepatocytes were similar to those seen in vivo, with the major routes of metabolism being N-dealkylation and/or hydroxylation. There was more extensive metabolic processing in hepatocytes than in microsomes; however, sequential metabolism was less extensive in vitro compared with in vivo. The pharmacokinetics of the three 5HT3 antagonists investigated were dominated by CYP3A4 (and/or 2C9) compared with CYP1A2 in man, possibly determined by enzyme capacity rather than relative enzyme affinity. These data support the use of rat, dog and human hepatocytes for the prediction of in vivo metabolites of ondansetron, alosetron and GR87442.

Potential employment of non-silica-based stationary phases in pharmaceutical analysis

The absolute majority of the HPLC applications use silica-based columns for the separation of active substance and its impurities. However, stationary phases based on metal oxides appear as an interesting alternative. The aim of our study was to investigate the potential utilization of metal oxide-based stationary phases in analytical evaluation of ondansetron and its five pharmacopoeial impurities. In our study commercially available ZrO(2)-based columns (e.g. Zr-PBD, Zr-PS, Zr-C18) and TiO(2)-based column were used. The effect of an organic modifier (type and ratio), a buffer (type, pH and concentration) and the influence of temperature was investigated. The separation of ondansetron and its five pharmacopoeial impurities was successfully accomplished on a Zirchrom-PBD column using a mobile phase consisting of acetonitrile-ammonium phosphate (25 mM, pH 7.0) (18:82, v/v). Detection was performed at 216 nm and the analysis was completed within 7.5 min. The paper proves metal oxide-based stationary phases as an alternative to classical silica-based stationary phases in pharmaceutical analysis.

Formulation and evaluation of ondansetron nasal delivery systems

This study aimed to formulate and evaluate nasal delivery systems containing ondansetron hydrochloride. In the in vitro study, the permeation rate with the addition of 10% polyethylene glycol 300 (PEG 300) to aqueous solution containing 0.01% benzalkonium chloride (BC) and 10% sulfobutylether beta-cyclodextrin sodium salt (SBCD) was somewhat more rapid up to 1.5h compared to the addition of 10% PG. The permeation flux increased as the drug concentration increased regardless of the vehicles used. The addition of nicotinamide or chitosan to aqueous drug solution (40 mg/ml) with 10% PEG 300 and 0.01% BC rather decreased permeation rate and delayed lag time. Even though cyclodextrins including SBCD or dimethyl-ss-cyclodextrin failed to show permeation enhancing effects of ondansetron hydrochloride, the addition of 10% SBCD to aqueous solution containing 10% PEG 300 and 0.01% BC could be a good candidate for ondansetron nasal delivery systems because of its safety profile, stable storage in refrigerator and solubilizing effect. With the above formulation, the nasal delivery system increased AUC0-2h and Cmax by 2.1 and 1.7 times compared to those of oral delivery, respectively while there was no difference found in AUC0-2h with intravenous administration. Therefore, the nasal delivery system of ondansetron hydrochloride formulated in this study was feasible for nasal administration.

Taste masking of ondansetron hydrochloride by polymer carrier system and formulation of rapid-disintegrating tablets

The purpose of this research was to mask the intensely bitter taste of ondansetron HCl and to formulate a rapid-disintegrating tablet (RDT) of the taste-masked drug. Taste masking was done by complexing ondansetron HCl with aminoalkyl methacrylate copolymer (Eudragit EPO) in different ratios by the precipitation method. Drug-polymer complexes (DPCs) were tested for drug content, in vitro taste in simulated salivary fluid (SSF) of pH 6.2, and molecular property. Complex that did not release drug in SSF was considered taste-masked and selected for formulation RDTs. The complex with drug-polymer ratio of 8:2 did not show drug release in SSF; therefore, it was selected. The properties of tablets such as tensile strength, wetting time, water absorption ratio, in vitro disintegration time, and disintegration in the oral cavity were investigated to elucidate the wetting and disintegration characteristics of tablets. Polyplasdone XL-10 7% wt/wt gave the minimum disintegration time. Tablets of batch F4 containing spray-dried mannitol and microcrystalline cellulose in the ratio 1:1 and 7% wt/wt Polyplasdone XL-10 showed faster disintegration, within 12.5 seconds, than the marketed tablet (112 seconds). Good correlation between in vitro disintegration behavior and in the oral cavity was recognized. Taste evaluation of RDT in human volunteers revealed considerable taste masking with the degree of bitterness below threshold value (0.5) ultimately reaching to 0 within 15 minutes, whereas ondansetron HCl was rated intensely bitter with a score of 3 for 10 minutes. Tablets of batch F4 also revealed rapid drug release (t(90), 60 seconds) in SGF compared with marketed formulation (t(90), 240 seconds; P < .01). Thus, results conclusively demonstrated successful masking of taste and rapid disintegration of the formulated tablets in the oral cavity.

Common pharmacophores for uncharged human ether-a-go-go-related gene (hERG) blockers

In silico approaches are widely used to predict human ether-a-go-go-related gene (hERG) channel blockade. Published pharmacophore models of hERG blockers typically contain a basic nitrogen center flanked by aromatic or hydrophobic groups. However, hERG blockade has been observed in series lacking the basic nitrogen. By utilizing screening data for 194 potent uncharged hERG actives, we propose a pharmacophore for neutral hERG blockers, and provide guidance on eliminating hERG liability in an uncharged hERG active chemical series.

Investigation of colon-specific dosage forms of ondansetron prepared with natural polymers

The aim of this study was to develop colon-specific delivery systems of ondansetron using natural polymers such as guar gum and sodium alginate. For this purpose colon specific matrix tablets were prepared by a direct compression method. The physical properties of the tablets were tested and in vitro release studies were performed by a flow-through cell apparatus. The amount of polymers affected the in vitro drug release from the matrix tablets. A high amount of polymers provided slow drug release whereas the release of ondansetron from the tablets prepared with low amount of polymers was found to be fast. Ondansetron-alginate and/or guar gum matrix tablet formulations can deliver the drug to the small and large intestine thus these matrix may be a promising system for the reduction of visceral sensitivity and inhibition of motor activity in irritable bowel syndrome (IBS).

Assignments of 1H and 13C NMR spectral data for ondansetron and its two novel metabolites, 1-hydroxy-ondansetron diastereoisomers

Assignments of 1H and 13C NMR chemical shifts were made by means of heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlation (HMBC) experiments for ondansetron, and by means of 1H-1H correlation spectroscopy (1H-1H COSY) and two-dimensional nuclear Overhauser effect spectroscopy (NOESY) experiments for two novel metabolites (M1 and M2) of ondansetron. These two metabolites were isolated for the first time from Mucor circinelloides.

[Preparation of ondansetron hydrochloride sustained-release tablet evaluation of its and drug release behavior in vitro]

For the purpose of preparing the ondansetron hydrochloride sustained-release tablets and studying the influencing factors, we prepared the ondansetron hydrochloride sustained-release tablets, using hydroxypropylmethylcellose (HPMC) as the matrix material. Then we investigated the effects of the viscosity and amount of HPMC,the sort of fillers, the preparation methods, the alcohol content in adhesives, and the pH of the dissolving solution on the release of ondansetron hydrochloride from sustained-release tablets. On the basis of pharmaceutical preformulation studies,the best formulation and preparation methods were screened out according to orthogonal experiment design method. The release behavior of the tablets followed the Higuchi equation. The viscosity of HPMC,the sort of fillers and the rotation speed had no significant effects on the release of ondansetron hydrochloride sustained-release tablets,while the preparation methods, the alcohol content in adhesives and the pH of the dissolving solution influcenced the release of ondansetron hydrochloride sustained-release tablets significantly. Ondansetron hydrochloride sustained-release tablets had good drug relase behavior for in 12 h in vitro.

[Preparation of ondansetron hydrochloride osmotic pump tablets and their in vitro drug release]

AIM

To prepare ondansetron hydrochloride osmotic pump tablets (OND-OPT) and investigate their in vitro drug release behavior.

METHODS

OND-OPT were prepared with a single punch press and pan coating technique. Osmotic active agents and plasticizer of coating film were chosen by drug release tests. The effects of the number, position and direction of drug release orifice on release behavior were investigated. The relation between drug release duration and thickness of coating film, PEG content of coating film and size of drug release orifice was established by uniform design experiment. The surface morphological change of coating film before and after drug release test was observed by scanning electron microscopy. The osmotic pumping release mechanism of OND-OPT was confirmed by drug release test with high osmotic pressure medium.

RESULTS

Lactose-mannitol (1:2) was chosen as osmotic active agents and PEG400 as plasticizer of coating film. The direction of drug release orifice had great effect on the drug release of OND-OPT without HPMC, and had no effect on the drug release of OND-OPT with HPMC. The OND-OPT with one drug release orifice at the centre of the coating film on one surface of tablet released their drug with little fluctuation. The drug release duration of OND-OPT correlated with thickness of coating film and PEG content of coating film, and didn't correlate significantly with the size of drug release orifice. OND-OPT released their drug with osmotic pumping mechanism predominantly.

CONCLUSION

OND-OPT are able to realize ideal controlled drug release.

Compatibility of ondansetron hydrochloride and methylprednisolone sodium succinate in multilayer polyolefin containers

PURPOSE

The compatibility of ondansetron hydrochloride and methylprednisolone sodium succinate in 5% dextrose injection and 0.9% sodium chloride injection was studied.

METHODS

Test solutions of ondansetron hydrochloride 0.16 mg/mL and methylprednisolone sodium succinate 2.4 mg/mL were prepared in triplicate and tested in duplicate. Total volumes of 4 and 2 mL of ondansetron hydrochloride solution and methylprednisolone sodium succinate solution, respectively, were added to 50-mL multilayer polyolefin bags containing 5% dextrose injection or 0.9% sodium chloride injection. Bags were stored for 24 hours at 20-25 degrees C and for 48 hours at 4-8 degrees C. Chemical compatibility was measured with high-performance liquid chromatography, and physical compatibility was determined visually.

RESULTS

Ondansetron hydrochloride was stable for up to 24 hours at 20-25 degrees C and up to 48 hours at 4-8 degrees C. Methylprednisolone sodium succinate was stable for up to 48 hours at 4-8 degrees C. When stored at 20-25 degrees C, methylprednisolone sodium succinate was stable for up to 7 hours in 5% dextrose injection and up to 24 hours in 0.9% sodium chloride injection. Compatibility data for solutions containing ondansetron hydrochloride plus methylprednisolone sodium succinate revealed that each drug was stable for up to 24 hours at 20-25 degrees C and up to 48 hours at 4-8 degrees C.

CONCLUSION

Ondansetron 0.16 mg/mL (as the hydrochloride) and methylprednisolone 2.4 mg/mL (as the sodium succinate) mixed in 50-mL multilayer polyolefin bags were stable in both 5% dextrose injection and 0.9% sodium chloride injection for up to 24 hours at 20-25 degrees C and up to 48 hours at 4-8 degrees C.

Transdermal Delivery of Ondansetron Hydrochloride: Effects of Vehicles and Penetration Enhancers

The effects of vehicles and penetration enhancers on the in vitro permeation of ondansetron hydrochloride (OS) across dorsal hairless mouse skins were investigated. Various types of vehicles, including ester, alcohol, and ether and their mixtures were used, and then a series of fatty acids and fatty alcohols were employed as enhancers. Among pure vehicles used, water and ethanol showed high permeation fluxes, which were 48.2+/-23.7 and 41.9+/-17.9 microg/cm2 per h, respectively. Even though propylene glycol monocaprylate (PGMC) alone did not show a high permeation rate, the skin permeability of OS was increased by the addition of diethylene glycol monoethyl ether (DGME); the highest flux was achieved at 40% of DGME. Also, the combination of PGMC and ethanol (80:20) or PGMC and propylene glycol (PG) (60:40) increased the permeation flux by six- and two-fold, respectively, compared to PGMC alone. The synergistic enhancement was also obtained by using PG-oleyl alcohol (OAl) cosolvent. The greatest flux was attained by the addition of unsaturated fatty acids at 3% concentration to PG. The enhancement factors with the addition of oleic acid or linoleic acid to PG were about 1250 and 450, respectively. But saturated fatty acids failed to show a significant enhancing effect. When the PGMC-DGME (60:40) cosolvent system was used as a vehicle, all fatty acids, including unsaturated fatty acids, failed to show significant enhancing effects. The results indicate that the combinations of oleic acid, linoleic acid, or oleyl alcohol with PG, or PGMC-DGME (60:40) cosolvent could be used for the design of the OS transdermal system.

Physical characteristics of polymer complexes in suspension obtained from cellulosic latexes with ondansetron

Ondansetron is a carbazol with antiemetic properties. It is used primarily to control nausea and vomiting caused by cytotoxic chemotherapy and radiotherapy, as well as in postoperative vomiting in gynecological surgery. Ondansetron has a half-life of approximately 4 h, hence it is a matter of great interest to determine the ideal conditions for the formation of a drug-polymer complex in order to prolong the duration of the therapeutic action. A stability study of the active drug was first carried out on each of the polymers (Aquateric and Aquacoat). The adsorption of ondansetron on the lattices was determined with respect to time, pH and concentration. The results obtained suggest that both polymers are suitable as drug carriers for the controlled-release formulations obtained. We conclude that an acid pH is evidently fundamental in the adsorption process of this drug in the latexes. Moreover, the Aquateric latex would seem to be the best-suited polymer to use as a vehicle for drug delivery.

X-ray diffraction and electron microscopy in the polymorphism study of ondansetron hydrochloride

Using different techniques, we studied the possible formation of ondansetron polymorphs. Ondansetron is a carbazol antiemetic that acts as a competitive, selective inhibitor of 5-HT3 serotonin receptors. The polymorphs were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results suggest that the compounds are not true crystallographic polymorphs, but instead are the product of physical structural changes in the drug, which would be of interest pharmaceutically.

Determination of ondansetron and its hydroxy metabolites in human serum using solid-phase extraction and liquid chromatography/positive ion electrospray tandem mass spectrometry

Ondansetron and its hydroxylated metabolites were determined in human serum using solid-phase extraction (SPE) and liquid chromatography/positive ion electrospray tandem mass spectrometry. Pyrimethamine was used as the internal standard. The analytes were eluted from the SPE cartridge using 2 x 1 ml of methanol containing 0.5% triethylamine, evaporated under vacuum and the residue was reconstituted in the mobile phase. The liquid chromatographic separation was achieved on a silica column using a mobile phase of aqueous 20 mM ammonium acetate (pH 4.7)-acetonitrile (85 : 15, v/v) at a flow-rate of 0.4 ml min(-1). The method was linear over the range 1-500 ng ml(-1) for ondansetron and each of the metabolites in human serum. The intra-day accuracy was better than 9.1% and the precision was <10.3%; the inter-day accuracy was better than 9.5% and the precision was <12.6%. The limit of detection was 250 pg ml(-1) based on a signal-to-noise ratio of 3. The absolute recovery from serum for all analytes was >90%.

Formation of ondansetron polymorphs

We used differential scanning calorimetry, infrared spectrophotometry and 1H nuclear magnetic resonance imaging to search for polymorphs of ondansetron. Samples were tested under different conditions of temperature, pulverization and pH, and in different solvents. The factors identified as able to cause the formation of polymorphs were heating to different temperatures for different times, and the use of ethanol and methanol as solvents.

Stability of ondansetron hydrochloride and 12 medications in plastic syringes

The stability and compatibility of ondansetron hydrochloride with neostigmine methylsulfate, naloxone hydrochloride, midazolam hydrochloride, fentanyl citrate, alfentanil hydrochloride, atropine sulfate, morphine sulfate, meperidine hydrochloride, propofol, droperidol, metoclopramide monohydrochloride, and glycopyrrolate were studied. Ondansetron 1.33 or 1.0 mg/mL was combined with 0.9% sodium chloride injection and each of the 12 drugs in duplicate in plastic syringes (or glass for propofol). The syringes were stored at 21.8-23.4 or 4 degrees C in the dark, except for those containing propofol, which were stored at ambient temperature. Samples were removed at 0, 4, 8, and 24 hours for analysis by high-performance liquid chromatography and pH measurement; the propofol-containing samples were removed at 0, 1, 2, and 4 hours. Syringes were visually assessed for color and clarity, and particulate content was measured with a particle counter at the end of the study period. All solutions containing ondansetron retained more than 90% of their initial ondansetron concentration. Solutions containing each of the other drugs except droperidol retained more than 90% of their initial concentration of these drugs. The solutions containing droperidol retained more than 90% of their initial droperidol concentration for up to eight hours at ambient temperature but precipitated quickly at 4 degrees C. In combinations of ondansetron 1.33 or 1.0 mg/mL and 10 of 12 drugs, all drugs were stable for 24 hours in plastic syringes at 23 and 4 degrees C; ondansetron hydrochloride 1.0 mg/mL and propofol 1.0 and 5.0 mg/mL in admixtures were stable for 4 hours, and droperidol on its own and combined with ondansetron 1.0 mg/mL was stable for no more than 8 hours at ambient temperature.

Enantioselective determination of S-(+)- and R-(-)-ondansetron in human serum using derivatized cyclodextrin-modified capillary electrophoresis and solid-phase extraction

A high-performance capillary electrophoresis (HPCE) assay method for the quantitation of S-(+)- and R-(-)-ondansetron in human serum was developed. Resolution was achieved using 15 mM heptakis-(2, 6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD) in 100 mM phosphate buffer (pH 2.5). A 72-cm untreated fused-silica capillary, at a constant voltage of 20 kV, was used for the analysis. A 0.03-mM cationic detergent was used as a buffer additive to decrease the adsorption of endogenous substances onto the silica wall. The analytes of interest were isolated from endogenous substances using a solid-phase extraction procedure. The cyanopropyl cartridge gave good recoveries in excess of 85% for both S-(+)- and R-(-)-ondansetron, without any interferences. To decrease the limits of detection of the analytes, an on-capillary sample concentration technique was employed. The detection limit was 10 ng/ml using 2 ml of serum and the limit of quantitation was 15 ng/ml. The calibration curve was linear over a range of 15-250 ng/ml, with procainamide as the internal standard, and the coefficients of determination obtained were greater than 0.999 (n = 3). Precision and accuracy of the method were 2.76-5.80 and 2.10-5.00%, respectively, for S-(+)-ondansetron, and 3.10-6.57 and 2.50-4.35%, respectively, for R-(-)-ondansetron. The HPCE method is a useful alternative to existing chiral high-performance liquid chromatographic methods.

Ondansetron hydrochloride: a competitive serotonin 5-HT3 receptor blocker

The methyl substituted imidazole ring in the title compound, 2-methyl-1-(9-methyl-4-oxo-2,3,4,9-tetrahydro-1H-carbazol-3-yl) imidazol-3-ium chloride dihydrate, C18H20N3O+.Cl-.2H2O, is approximately perpendicular to the carbazole plane [dihedral angle 87.0(1) degrees]. The water molecules are involved in an elaborate network of hydrogen bonds that reinforce the stability of the dihydrate and the cohesion of the structure.

Compatibility of ondansetron hydrochloride with meperidine hydrochloride for combined administration

OBJECTIVE

To determine the physical compatibility and chemical stability of ondansetron hydrochloride 0.1 and 1 mg/mL with meperidine hydrochloride 4 mg/mL admixed in NaCl 0.9% injection USP.

DESIGN

Triplicate test solutions of the drugs in NaCl 0.9% injection USP were prepared and stored at 4, 22, and 32 degrees C. Samples were removed initially and at various time points over 31 days and were stored at -70 degrees C until they were analyzed. Physical compatibility was assessed by measuring solution turbidity with a color-correcting turbidimeter and particle content with a light-obscuration particle sizer/counter, as well as by visual assessment. Chemical stability of the drugs was determined using a stability-indicating HPLC analytic method. Duplicate determinations were performed on each sample to measure the concentration of each drug.

RESULTS

All admixtures were found to exhibit no visual or subvisual changes of consequence in turbidity or particle content at all observation points. Further, little or no loss of any of the drugs occurred in any concentration throughout the study.

CONCLUSIONS

The physical compatibility and chemical stability of ondansetron hydrochloride with meperidine hydrochloride under the conditions of this study have been established for 7 days at 32 degrees C and 31 days at 4 and 22 degrees C.

Stability of ondansetron hydrochloride injection in various beverages

The stability of ondansetron hydrochloride injection in beverages likely to be acceptable to patients was studied. Ondansetron hydrochloride injection (containing ondansetron 2 mg/mL) was added to apple juice, fruit punch, cherry-flavored drink, carbonated soft drinks, and hot tea to provide a nominal ondansetron concentration of 32.8, 64.5, or 95.2 micrograms/mL. Samples were stored at -3 to 28 degrees C (noncarbonated-beverage mixtures except tea), 2 to 28 degrees C (carbonated-beverage mixtures), and 25 degrees C (tea) and assayed for ondansetron concentration by high-performance liquid chromatography at 6, 24, 48, and 72 hours (noncarbonated-beverage mixtures except tea); 6, 24, and 48 hours (carbonated-beverage mixtures); and 1 hour (tea). More than 95% of the initial ondansetron concentration was retained in apple juice, fruit punch, cherry-flavored drink, Sprite, and Diet Coke throughout the periods studied. A precipitate formed immediately after ondansetron was added to hot tea, but the drug was chemically stable for at least one hour in this preparation. Ondansetron hydrochloride injection 32.7, 64.5, and 95.2 micrograms/mL (expressed as free base) was stable in various beverages when stored at -3 to 28 degrees C for up to 72 hours. Ondansetron at these same concentrations precipitated in hot tea preparations but was chemically stable for at least one hour.

Ondansetron clinical pharmacokinetics

Ondansetron is a potent and highly selective serotonin 5-HT3-receptor antagonist which has demonstrated important antiemetic activity and good tolerability in the prevention of chemotherapy-induced nausea and vomiting. Ondansetron is completely and rapidly absorbed from the gastrointestinal tract after oral administration, and does not accumulate with repeated oral administration. Owing to hepatic first-pass metabolism, its bioavailability is only about 60% compared with ondansetron administered by infusion over 15 minutes. Bioavailability is slightly increased when administered after a standard meal, and is not influenced by coadministration of antacids; a slightly enhanced bioavailability has been observed in patients with cancer. Since the time to reach peak concentration is 0.5 to 2 hours after oral ingestion, the drug should be administered at least 30 minutes before chemotherapy. Possible alternative ways of administration of ondansetron include intramuscular, subcutaneous and rectal administration, and oral controlled-release formulations. Ondansetron is widely distributed (volume of distribution approximately 160L) and binds moderately (70 to 76%) to plasma proteins; the elimination half-life averages approximately 3.8 +/- 1 hours. Clearance occurs by hepatic metabolism (95%) rather than renal excretion. Metabolites do not play a role in the activity of the drug, and there is no evidence of genetic polymorphic metabolism. Although aging is associated with decreased clearance and increased bioavailability, dosage adjustments are not required for the elderly, and may be necessary only in patients with severe hepatic impairment. Chemotherapeutic agents do not seem to modify the pharmacokinetics of ondansetron. There remains the question of whether control of emesis is related to systemic availability of ondansetron and, in consequence, the optimal dose and schedule of ondansetron is still to be identified with certainty.

Molecular surface comparison. 2. Similarity of electrostatic vector fields in drug design

In the first article of this series a real-time graphics method was described for molecular similarity of scalar properties. This has now been extended for the comparison of molecular vector properties, most notably electrostatic field. A comparison of the various techniques of calculating fields is presented that includes a new method based on natural orbital fitted point charges. In the two examples described, namely, a series of benzodiazepine agonists and a set of serotonin 5-HT3 antagonists, the program has been shown to produce useful pharmacophoric overlaps that can be used in the design of novel therapeutic agents.

Compatibility and stability of ondansetron hydrochloride with morphine sulfate and with hydromorphone hydrochloride in 0.9% sodium chloride injection at 4, 22, and 32 degrees C

The physical compatibility and chemical stability of ondansetron hydrochloride 0.1 and 1 mg/mL with morphine sulfate 1 mg/mL and with hydromorphone hydrochloride 0.5 mg/mL in 0.9% sodium chloride injection were studied. Test solutions of the drugs in 0.9% sodium chloride injection were prepared in triplicate and stored at 4, 22, and 32 degrees C. Samples were removed immediately and at various time points over 31 days and stored at -70 degrees C until analyzed. Physical compatibility was assessed visually and by measuring turbidity with a color-correcting turbidimeter and particle content with a light-obscuration particle sizer and counter. Chemical stability was determined by measuring the concentration of each drug in duplicate with stability-indicating high-performance liquid chromatography. There were no visual or subvisual changes in turbidity or particle content in any of the test solutions at any of the time points. There was little or no loss of any of the drugs. When admixed in 0.9% sodium chloride injection, ondansetron hydrochloride 0.1 and 1 mg/mL plus morphine sulfate 1 mg/mL or hydromorphone hydrochloride 0.5 mg/mL were compatible and stable for at least 7 days at 32 degrees C and for at least 31 days at 4 and 22 degrees C.

Stability of ondansetron stored in polypropylene syringes

OBJECTIVE

To evaluate the stability of ondansetron hydrochloride undiluted and mixed in dextrose 5% injection or NaCl 0.9% injection during storage in polypropylene syringes when frozen, refrigerated, or at room temperature.

DESIGN

Batch quantities of ondansetron 0.25, 0.5, 1.0, and 2.0 mg/mL were prepared and individual doses of 10.5 mg were drawn into polypropylene syringes that were stored at -20 degrees C for up to 3 months, at 4 degrees C for up to two weeks, or at 22-25 degrees C for two days, and various combinations of these conditions. At defined sampling times aliquots were withdrawn from syringes, the solution visually inspected, pH measured, and ondansetron concentration determined by HPLC. Drug loss of > or = 10 percent of the original content of the solution was considered clinically significant.

RESULTS

The ondansetron concentration in each solution, regardless of storage conditions, remained above 90 percent of the original concentration at each observation time (range 92-107 percent). No changes in color or clarity of any of the solutions were observed, and only slight fluctuations in pH (< or = 0.05) were noted.

CONCLUSIONS

Ondansetron 2 mg/mL undiluted, or at concentrations of 0.25, 0.5, or 1 mg/mL, mixed in dextrose 5% injection or NaCl 0.9% injection was determined to be stable when stored in polypropylene syringes for each storage condition at all time points studied, including the maximum for each: three months at -20 degrees C, followed by 14 days at 4 degrees C, and by 48 hours at 22-25 degrees C.

Stability of paclitaxel with ondansetron hydrochloride or ranitidine hydrochloride during simulated Y-site administration

The stability of paclitaxel with either ondansetron hydrochloride or ranitidine hydrochloride during simulated Y-site injection at room temperature was studied. Triplicate test solutions of paclitaxel 0.3 and 1.2 mg/mL were admixed 1:1 with ondansetron 0.03 and 0.3 mg/mL (as the hydrochloride salt) or ranitidine 0.5 and 2.0 mg/mL (as the hydrochloride salt). Also, paclitaxel 1.2 mg/mL was admixed 1:1:1 with ondansetron 0.3 mg/mL and ranitidine 2.0 mg/mL. The solutions were stored in glass containers at room temperature, and samples were removed at zero, one, two, and four hours for immediate assay. At the time of the assay and before any dilution, each sample was visually inspected for clarity, color, and precipitation, and the pH was determined. Drug concentrations were measured by stability-indicating high-performance liquid chromatographic procedures. Throughout the study, more than 90% of the initial concentrations of paclitaxel, ondansetron, and ranitidine remained in the solutions. No precipitates, color changes, or haziness was seen. The changes in pH were minor. Paclitaxel in concentrations of 0.3 and 1.2 mg/mL was stable when mixed with either ondansetron (0.03 or 0.3 mg/mL, as the hydrochloride salt) or ranitidine (0.5 or 2.0 mg/mL, as the hydrochloride salt) and stored in glass containers for four hours. Paclitaxel 1.2 mg/mL was also stable when mixed with both ondansetron 0.3 mg/mL and ranitidine 2.0 mg/mL and stored in glass containers for four hours.

Development of high-affinity 5-HT3 receptor antagonists. Structure-affinity relationships of novel 1,7-annelated indole derivatives

On the basis of the structures of ondansetron and GR 65,630, its ring-opened C-linked methylimidazole analogue, novel 1,7-annelated indole derivatives were synthesized as potential 5-HT3 antagonists. Receptor binding studies show that all compounds display a high affinity for the 5-HT3 receptors. In both series annelation results in compounds being 7 and 4 times more potent than the references ondansetron and GR 65,630, respectively. Similar to ondansetron, the 1,7-annelated indoles show little stereoselectivity. The (-)-isomers are only slightly more potent than the (+)-isomers. The receptor binding profile of l-10-[(2-methyl-1H-imidazol-1-yl)methyl]-5,6,8,9,10,11-hexahydro-4H-pyri do [3,2,1-jk]carbazol-11-one hydrochloride (24b) (INN cilansetron) shows that the compound displays, besides a high affinity for 5-HT3 receptors (Ki = 0.19 nM), a weak affinity for sigma-receptors (Ki = 340 nM), muscarine M1 receptors (Ki = 910 nM), and 5-HT4 receptors (Ki = 960 nM) and no affinity (Ki > or = 5000 nM) for all the other receptor types tested (n = 37). The new compounds fit the proposed necessary chemical template for binding: a heteroaromatic ring system, a coplanar carbonyl group, and a nitrogen center at well-defined distances. The enhanced potency of the annelated 1,7-indole derivatives indicates that the extra ring provides a favorable hydrophobic area for interaction with the 5-HT3 receptor site. In vivo cilansetron is more potent and induces less central side effects than ondansetron. At present cilansetron is in clinical trials.