Enhanced in vivo absorption of CB-1 antagonist in rats via solid solutions prepared by hot-melt extrusion.

The aim of the present work was to investigate in vitro dissolution properties of three binary solid solutions prepared by a hot-melt extrusion (HME) process with vinyl pirrolidone--vinyl acetate copolymer (Kollidon VA 64), ethyl acrylate, methyl methacrylate polymer (Eudragit E) polyetilenglicol 8000 (PEG 8000) with a cannabinoid type 1 (CB-1) antagonist. Hansen solubility parameters were calculated from the chemical structures of the drug and the individual polymers in order to predict miscibility. Solid state characterizations of drug substance, physical blends and HME formulations were performed with differential scanning calorimetry. The dissolution testing conducted under sink conditions revealed that the dissolution rate of HME formulations improved around 1.8-fold vs drug substance. Supersaturation dissolution study demonstrated that HME formulations composed by Eudragit E and Kollidon VA64 increased drug solubility between 30- and 35-fold, respectively comparing to the drug substance. Physical and chemical stability of formulations were studied at 40°C/75%HR with open dish during 15 days. The formulation composed by the drug and Eudragit E at 10:90 was evaluated for in vivo drug absorption in male Wistar-Hannover rats and it was found to increase CB-1 absorption threefold greater than pure drug oral suspension.

Enantioseparation of basic pharmaceutical compounds by capillary electrophoresis using sulfated cyclodextrins. Application to E-6006, a novel antidepressant.

In this study, a chiral capillary electrophoresis method was optimized and validated for E-6006, a thienylpyrazolylethanamine derivative (pKa 8.9). Enantioselectivity of neutral and anionic cyclodextrins (CDs) was evaluated at acid pH (3), obtaining cathodic and anodic migration, respectively. Hydroxypropyl-beta-CD, carboxymethyl-beta-CD and sulfobutyl ether-beta-CD led to similar and partial selectivity, whereas sulfate (S)-beta-CD produced baseline separation of the enantiomers. Four types of sulfated CDs were compared considering: cavity size (alpha, beta, gamma) and random substitution versus unique derivative (S-beta-CD, 6-heptakis-S-beta-CD). Complete peak separation was obtained in all cases, but with different affinity and binding strength. Some factors that play a role in the complex formation include: position/region/degree of substitution, size of CD cavity and proportion of derivatives in mixtures. Enantioaffinity and enantioselectivity increased with the average of sulfate groups/mol. Beta cavity size complexed better, although alpha and gamma cavities did not compromise separation. 6-Heptakis-S-beta-CD had less affinity and separation efficiency, attributed to its lower degree and unique position of substitution. The method was optimized with S-beta-CD (Aldrich, randomly substituted, 7-11 groups/mol). With this selector, the effect of pH value (3-9) was evaluated. Around pH 7 the cross-over point with change in the direction and order of migration was observed, associated with great enantioselectivity and long migration times. Fine tuning was done by adjusting the CD concentration and the buffer counterion. Definitive conditions were: uncoated silica capillary, 10 mM S-beta-CD-25 mM sodium phosphate, pH 3. Validation parameters are included.

Simultaneous separation of the enantiomers of cizolirtine and its degradation products by capillary electrophoresis.

The simultaneous enantioselective separation of (+/-)-cizolirtine and its impurities: (+/-)-N-desmethylcizolirtine, (+/-)-cizolirtine-N-oxide and (+/- )-5-(alpha-hydroxybenzyl)-1-methylpyrazole was investigated by capillary electrophoresis. Electrokinetic chromatography with carboxymethyl-beta-CD (CM-beta-CD) and sulfobutyl-ether-beta-CD was tried, showing good enantioseparation but poor chemical selectivity. The four racemic pairs were baseline separated, in a single run, by cyclodextrin-modified micellar electrokinetic chromatography. The migration buffer composition was: (60 mM hydroxypropyl-beta-cyclodextrin-150 mM sodium dodecyl sulfate-50 mM disodium tetraborate, pH 9.2, in water)-butanol 95:5, v/v). Work was done to determine the effect of buffer components and their optimal concentration on selectivity. The method was validated with respect to enantioselectivity of cizolirtine as well as its degradation products and separation selectivity between the different components. Linearity, limit of detection, limit of quantitation and precision were also determined. This method is suitable for the enantiomeric purity determination and stability control of cizolirtine (racemic mixture or enantiomers) and its degradation products. Examples of electropherograms of (R)-cizolirtine degraded under stressed conditions are shown.

7-Azetidinylquinolones as antibacterial agents. 3. Synthesis, properties and structure-activity relationships of the stereoisomers containing a 7-(3-amino-2-methyl-1-azetidinyl) moiety.

A series of stereochemically pure 7-(3-amino-2-methyl-1-azetidinyl)-1,4- dihydro-6-fluoro-4-oxoquinoline- and -1,8-naphthyridine-3-carboxylic acids, with varied substituents at the 1-, 5-, and 8-positions, was prepared to determine the effects of chirality on potency and in vivo efficacy relative to the racemic mixtures (for part 2, see: J. Med. Chem. 1994, 37, 4195-4210). A series of chiral 9-fluoro-2,3-dihydro-3-methyl-7-oxo-10-(substituted-1- azetidinyl)-7H-pyrido[1,2,3- de]-1,4-benzoxazine-6-carboxylic acids was synthesized to study the effect of the azetidine moiety on tricyclic quinolone antibacterial agents. A series of amino acid prodrugs of chiral naphthyridines 24a and 24b and quinolone 33a (cetefloxacin) was prepared and evaluated for antibacterial activity, solubility, and pharmacokinetic behavior. The absolute configuration of the new azetidinylquinolones was established by X-ray analysis of one of the diastereomeric salts of the resolved azetidinols (15) and of compound 25a (E-4767), which showed the best in vitro and in vivo overall profile. Structure-activity relationship studies indicated that the absolute stereochemistry at the asymmetric centers of both the azetidine and the oxazine rings was critical to increase in vitro activity and oral efficacy. The 3S configuration in the pyridobenzoxazine series and the (2S,3R) configuration of the 3-amino-2-methylazetidine moiety for all new compounds conferred the best antibacterial activity.

Determination of benzalkonium chloride in aqueous ophthalmic preparations by high-performance liquid chromatography.

A high-performance liquid chromatographic method is described for the determination of homologues of benzalkonium chloride in aqueous ophthalmic preparations. The technique involves direct injection of the sample on a 5-microns Spherisorb-CN column. The mobile phase is acetonitrile-triethylamine (0.1%, v/v) in water (pH 2.5; 40:60, v/v). Detection is carried out at 215 nm. The method is rapid, specific, reproducible and simple, and is especially useful for the assay of this preservative in stability studies and quality control procedures.

HPLC method for the simultaneous determination of pilocarpine, isopilocarpine, pilocarpic acid and isopilocarpic acid.

A high-performance liquid chromatographic method suitable for the determination of pilocarpine, isopilocarpine, pilocarpic acid and isopilocarpic acid is described. The column used is a Spherisorb-CN bonded phase at 25 degrees C. An aqueous solution of triethylamine (0.1%, v/v) at pH 2.5 is used as mobile phase. Peak detection is by UV absorption at 220 nm. The elution orders are found to be pilocarpic-isopilocarpic acids with a resolution of 9 and K' of 5 and 6, respectively, isopilocarpine-pilocarpine with a resolution of 1.8 and K' of 13 and 13.5, respectively, the peaks being symmetrical.