Identification and purity test of heparin by NMR - a summary of two years' experience at the Medical Products Agency.

This paper is a review of published and unpublished results on heparin during the last two years. Results and experiences gathered in our laboratory at MPA in Sweden, from the collaborative NMR study on heparin in Europe (coordinated by EDQM), and from the process of drafting heparin Ph. Eur. monograph texts where new ideas and experiments have been performed. Explanations and guidelines are also presented to clarify the NMR identification test introduced in the sodium and calcium heparin monographs. NMR, strong anion exchange-LC (SAX-LC) and capillary electrophoresis (CE) have been compared in the quantification of over-sulphated chondroitin sulphate (OSCS) and dermatan sulphate (DS) in heparin. In this paper, the term heparin will stand for unfractionated porcine heparin sodium. When other heparin types are mentioned, they will be explicitly named.

Validation of different microdialysis methods for the determination of unbound steady-state concentrations of theophylline in blood and brain tissue.

Three microdialysis methods, the "tritium" method, the "point-of-no-net-flux" method, and a method using the low perfusion rate of 0.1 microliter/min, were compared with respect to their ability to generate estimates of unbound steady-state concentrations (Cu(ss)) of the antiasthmatic drug theophylline in blood and brain tissue in anesthetized rats. Concomitantly, the influence of the perfusion flow rate on the estimated extracellular Cu(ss) obtained with the point-of-no-net-flux method was investigated. Theophylline was administered as a rapid intravenous bolus dose followed by constant intravenous infusion. Changes in perfusion flow rate from 2.0 to 0.75 microliter/min and, finally, to 0.25 microliter/min, using the point-of-no-net-flux method, had no significant effect on the estimated Cu(ss) of theophylline in blood and striatum. This observation, particularly in the case of brain tissue, is not consistent with the theory that the process of dialysis drains a significant amount of substance from the immediate vicinity of the dialysis probe. Similar estimates of Cu(ss) in blood as well as in brain tissue were obtained with all three methods. Their accuracy in estimating Cu(ss) in blood was further strengthened by observations of unbound fractions similar to those reported in the literature. Furthermore, all three methods gave striatum/blood ratios at steady state of approximately 0.5, indicating that there is active transport of theophylline from brain tissue. It is concluded that the tritium method, when validated, can be used to study the time course of unbound drug concentrations in blood and tissues.

Pigmentation of kidneys and lymph nodes of mesocolon in rats fed diets containing the laxative danthron.

The tumor-promoting activity of the anthraquinone laxative danthron was studied by giving 3 groups of male rats a single subcutaneous injection of the colon tumor-inducing agent 1,2-dimethylhydrazine (DMH). After 1 week, the animals were fed diets containing 0, 600 or 2400 ppm of danthron for 26 weeks. Two other groups of rats were included in the study; one received no treatment while the other was given danthron only. Altogether 9 tumors were observed among animals given DMA with or without danthron. The incidence of colon tumors was higher in animals receiving DMH and danthron than in those given DMH only (5/60 vs. 0/30), but this difference was not statistically significant. The kidneys and lymph nodes of mesocolon were enlarged and showed a yellowish-red and brown discoloration, respectively. The pigment mostly displayed a PAS-positive reaction but contained no lipid as determined by several staining procedures. The available evidence suggests that the pigment is drug-derived.