No abstract

In this study, a kinetic model of the final bleaching stage with hydrogen peroxide in a totally chlorine free (TCF) bleaching sequence for ALCELL@ processed pulp was developed. The model was based on the rate of chromophore destruction characterized by the decrease in the light absorption coefficient of bleached pulp at 457 tun, C,. Based on the fact that the chromophore destruction proceeds rapidly in an initial phase followed by a much slower reaction during which a "floor-level" chromophore concentration is approached asymptotically, we propose that the hydrogen peroxide stage of the ALCELL@ derived pulp in the studied TCF sequence consists of two distinct phases, The initial phase is a very fast reaction. The rate equation of the second phase was determined as:which is valid in a pH range of 10.5 to 11.5 and a temperature range of 60 to 92.5"C.Dans cette etude, on a mis au point un modele cinetique de la phase finale de blanchiment avec du peroxyde d'hydrogene dans une sequence de blanchiment sans chlore (TCF) pour la mise en plte par le procede ALCELL@. Le modele est base sur la vitesse de destruction de chromophore caracterisee par la diminution du coefficient d'absorption de la lumiere de la plte blanchie a 457 nm, C , . En tenant compte du fait que la destruction de chromophore s'effectue rapidement dans une phase initiale suivie d'une reaction beaucoup plus lente au cours de laquelle une concentration "plancher" en chromophore est atteinte asymptotiquement, nous proponsons que la phase du peroxyde d'hydrogbne de la plte ALCELL@ dans la sequence TCF Btudiee comprenne deux phases distinctes: une phase initiale correspondant a une reaction tres rapide et une seconde phase dont I'equation cinktique est determinee cornme etant: -5 = 1.41 x 10" e~p(-69610/RT)[HOO-]~.'[C~ -CKS]* dt et qui est valide dans une gamme de pH de 10,s a 11,5 et une gamme de temperatures de 60 a 92,S"C.

The pharmacodynamics, pharmacokinetics, metabolism, and excretion of 14C‐sumatriptan have been studied in the beagle dog following administration by the intranasal and other routes. The pharmacological response which was monitored, an increase in carotid arterial vascular resistance, correlated with the plasma levels of unchanged sumatriptan following intranasal, intravenous, or intraduodenal administration to the anaesthetised dog. The pharmacokinetics and metabolism of sumatriptan were then confirmed in conscious male and female dogs. Intranasal administration of 14C‐sumatriptan resulted in rapid absorption of part of the dose. The overall bioavailability of sumatriptan was 40–50%. Sumatriptan was eliminated from plasma with a half‐life of 1·5 or 1·9 h after intravenous or intranasal dosage respectively. Radioactivity was largely excreted in urine (up to 75% of the dose) with small amounts in the bile and faeces after intravenous and intranasal dosing, as sumatriptan and a major metabolite. The results from these studies suggest that intranasal administration provides a viable method for delivering sumatriptan to the systemic circulation. © 1997 John Wiley & Sons, Ltd.

GR43175 is a selective 5-HT1-like receptor agonist which is effective in the acute treatment of migraine. Rats and dogs were dosed intravenously (iv) and orally (po) with 1 mg 14C-GR43175 base (as succinate salt)/kg bodyweight. GR43175 is rapidly absorbed after oral dosing. In dog, 95–100% of the dose is absorbed, but less (25–30%) is absorbed by the rat. The bioavailability is >54% in dog, but lower in rat. Except for the CNS, drug-related material is widely distributed after iv dosing, but is mainly concentrated in the gastrointestinal tract and excretory organs after oral dosing. GR43175 is eliminated from plasma by a combination of renal and metabolic clearance. Some first-pass metabolism occurs in both species. In dog the major route of excretion is in urine (78–83% of the dose) after either route of administration. In rat, urine is also the major route of excretion (71%) after iv dosing. After oral dosing to the rat the major route of excretion is in the faeces (83%). GR43175 is extensively metabolized, after either route of administration, in both species. GR49336, the indole acetic acid derivative of GR43175, is the major metabolite in dog and a major metabolite in rat.