Preparation of spray-dried microspheres of indomethacin and examination of the effects of coating on dissolution rates

In this study, microspheres were prepared by the spray drying technique using suspensions of indomethacin (IM) as active substance and coated by three different polymers in order to increase the dissolution rate of IM. Water solutions (0.1, 0.2 and 0.5%) of hydroxypropylmethyl cellulose (HPMC), polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC) were used as coating materials. Polyethylene glycol 400 (PEG 400) was added to all formulations as plasticizer. Changes of particles size and surface characteristics of the coated products were examined using optical microscopy and scanning electron microscopy (SEM), respectively. The effects of coatings on the dissolution rates of IM were examined using USP XXIII Method II in water and phosphate buffer pH 7.4. It was observed that coating the IM particles with HPMC, PVA and HPC polymers using the Spray-Drying Technique increased the dissolution rate of IM significantly.     

Arousal thresholds during human tonic and phasic REM sleep

The goal of the present study was to investigate arousal thresholds (ATs) in tonic and phasic episodes of rapid eye movement (REM) sleep, and to compare the frequency spectrum of these sub‐states of REM to non‐REM (NREM) stages of sleep. We found the two REM stages to differ with regard to behavioural responses to external acoustic stimuli. The AT in tonic REM was indifferent from that in sleep stage 2, and ATs in phasic REM were similar to those in slow‐wave sleep (stage 4). NREM and REM stages of similar behavioural thresholds were distinctly different with regard to their frequency pattern. These data provide further evidence that REM sleep should not be regarded a uniform state. Regarding electroencephalogram frequency spectra, we found that the two REM stages were more similar to each other than to NREM stages with similar responsivity. Ocular activity such as ponto‐geniculo‐occipital‐like waves and microsaccades are discussed as likely modulators of behavioural responsiveness and cortical processing of auditory information in the two REM sub‐states.