Chemical and biological integration of a mouldable bioactive ceramic material capable of forming apatite in vivo in teeth.

Chemically bonded ceramics have several advantages compared with conventional ceramics to be used as biomaterials. Especially the possibilities to harden the material at room temperature and to control the rheology are very beneficial. This paper investigates the interface formed in vivo between a calcium aluminate based dental filling material and teeth. Class 1 occlusal fillings were made in wisdom teeth and extracted after up to four weeks. Polished cross-sections of the teeth were studied with scanning electron microscopy (SEM), focused ion beam microscopy (FIB) and transmission electron microscopy (TEM). In order to analyse the distribution of elements at the interface elemental mapping was performed using STEM and EDX. The results showed that a tight bond forms between the filling material and tooth and no gap could be found even at high magnification. A 100-200 nm wide zone with an increase in oxygen was detected in the enamel next to the filling. The zone was denser than the rest of the enamel. Elemental mapping indicated an increase of silicon and a decrease of Ca at the interface. Dark field imaging and EDX mapping showed that the calcium aluminate system formed apatite in situ during hardening through precipitation.

Mechanical properties of a permanent dental restorative material based on calcium aluminate.

This paper deals with some important mechanical properties (hardness, dimensional stability, compressive and flexural strength) of an experimental version of a translucent calcium aluminate dental restorative material. All samples investigated have been made from pre-pressed tablets, with a compaction degree of approximately 60%, hydrated using a 0.15 wt % Li salt solution as an accelerator. The samples were stored in water at 37 degrees C between the measurements. As reference materials one composite, Tetric Ceram, and one glass ionomer, Fuji II, were used with specimens prepared according to the manufacturer's recommendations. For the reference materials some of the properties were published data. The results show that the calcium aluminate material has sufficient mechanical properties to be used as a permanent dental restorative taking as a reference the ISO 9917 and the ISO 4049 as well as the reference materials. In addition the results indicate that the mechanical properties are controlled by the microstructure, which is mainly determined by the grain size of the filler.

Colonic N-acetylation of 5-aminosalicylic acid in inflammatory bowel disease.

5-Aminosalicylic acid presently is believed to represent the therapeutically active moiety of the sulfasalazine molecule in the treatment of inflammatory bowel disease. The metabolism of this compound, however, has not been studied in detail. In this paper we provide evidence that 5-aminosalicylic acid is acetylated to N-acetyl-aminosalicylic acid in homogenates from colonic biopsy specimens (370 +/- 20 nmol/g wet wt or 2.9 +/- 0.9 nmol/mg.min, n = 10), whereas acetylation in fecal samples was only small (13.0 +/- 3.0 nmol/g). Mucosal N-acetylation was rapid, cofactor- and pH-dependent, and could be enriched in the cytosolic fraction. In contrast, fecal acetylation was slow and did not depend on the presence of acetyl-coenzyme A. There were neither significant differences of acetylation between patients and controls nor a significant correlation to the individual acetylation phenotype. From our results we believe that presystemic acetylation of 5-aminosalicylic acid may be mainly mediated by a colonic mucosal enzyme and only to a small extent by fecal (bacterial) processes.

Olsalazine-O-sulphate: an acid labile metabolite of olsalazine.

The discovery of an acid labile metabolite of olsalazine, tentatively identified as olsalazine-O-sulphate, is described. Due to its acid labile properties, this conjugate was previously co-determined with olsalazine. Based on this finding, a new assay has been developed making it possible to determine both olsalazine and olsalazine-O-sulphate simultaneously. The initial aim of this study was to simplify an original analytical method in order to improve sample throughput without loss of sensitivity. However, during this work, a previously unidentified acid labile metabolite was discovered. The characterization of this metabolite is described here.

The pharmacokinetics of olsalazine sodium in healthy volunteers after a single i.v. dose and after oral doses with and without food.

Olsalazine sodium (5,5'-azodisalicylic acid (OLZ] was given to eight healthy volunteers as a 10 mg i.v. bolus dose and as a 1 g oral dose with and without food. To five fasting participants single oral doses of 2 g and 4 g were given. Blood and urine were collected during three weeks after each dose and were assayed for OLZ, a conjugate identified as a sulphate of OLZ (OLZs), 5-aminosalicylic acid (5-ASA), and N-acetyl-5-aminosalicylic acid (ac-5-ASA). The study showed that: 1. OLZ had a very short elimination half-life, mean 56 min. 2. OLZ was absorbed from the intestinal tract to a very small extent, as seen from the low systemic availability and low urinary excretion, 2.3% and 0.31% respectively, for a 1 g dose taken fasting. 3. OLZ was present in the serum partly as a conjugate, which was identified as an O-sulphate. Following the i.v. dose the serum half-life of the O-sulphate was estimated to be 7 days. 4. Food intake did not influence the systemic availability of OLZ and ac-5-ASA. 5. There was no dose-dependent increase of OLZ absorption with single doses up to 2 g, but a 4-g dose showed a more than two-fold increase in the individual peak serum concentration and in the systemic availability of OLZ. However, there was no significant increase in the mean residence time (MRT) for OLZ or in the serum concentration of either 5-ASA or ac-5-ASA at a dose of 4 g.

The pharmacokinetics of sulphasalazine in young and elderly patients with rheumatoid arthritis.

The clinical pharmacokinetics of enteric-coated sulphasalazine (Salazopyrin-EN) were studied after acute and chronic dosing in 20 patients with 'active' rheumatoid arthritis. 12 elderly (mean age 74.4 +/- 1 yr; range 71-83) and 8 young (mean age 40.5 +/- 1.4 yr; range 35-46) patients were given a single 2 g oral dose of sulphasalazine after an overnight fast. Serum and urine samples were collected at regular intervals over a 96 hour period for estimation of concentrations of sulphasalazine, sulphapyridine and its metabolites. This procedure was repeated after 17 days of continuous treatment with salazopyrin-EN 2 g daily in order to compare the drug's kinetics at 'steady-state'. Whilst the interindividual variation in kinetic parameters was large, age and acetylator status had a significant influence on a number of factors. The elimination half-life of sulphasalazine was prolonged in the elderly whilst renal clearance was increased in slow acetylators at 'steady-state'. The tmax and apparent volume of distribution of sulphapyridine were increased in the elderly after a single drug dosage but these differences disappeared with regular dosing. The Cmax, elimination half-life, 'steady-state' serum concentration, apparent volume of distribution and total clearance of sulphapyridine were all affected by acetylator status. We conclude that old age has only a minor effect on the body's handling of sulphasalazine and sulphapyridine but that acetylator phenotype plays a significant role in determining the 'steady-state' serum concentrations of sulphapyridine. This is likely to have practical implications with regard to some of the drug's adverse effects.

Determination of salicylazosulphapyridine, sulphapyridine and its metabolites in serum and urine.

Methods for the determination of salicylazosulphapyridine (Salazopyrin(R)), sulphapyridine, N-acetylsulphapyridine, sulphapyridine-O-glucuronide and N-acetylsulphapyridine-O-glucuronide in serum and urine have been developed. In one method samples were diluted with methanol to precipitate proteins present and thereafter injected directly onto the liquid chromatographic column. The sulphapyridine-O-glucuronide could not be determined by this method. For the determination of all the main sulphapyridine metabolites the sulphapyridine aglycones were formed after treatment with beta-glucuronidase. These sulphapyridine compounds were then extracted with isobutylmethyl ketone at pH 5, and re-extracted to a phosphate buffer at pH 13 prior to injection. Separation and retention of all compounds was affected both by pH and concentration of methanol in the mobile phase. The proposed method made determinations down to 1 mug ml(-1) possible, which was found to be sufficient. Comparisons were made with spectrophotometric methods.

Simultaneous determination of ketobemidone and its N-demethylated metabolite in patient plasma samples by gas chromatography mass spectrometry with selected ion monitoring.

An analytical procedure has been developed for the simultaneous determination of ketobemidone and its N-demethylated metabolite, norketobemidone. After isolation from plasma and re-extraction to acidic aqueous phase, the two aminophenols were extracted as ions pairs with tetrabutylammonium to dichloromethane, where derivatization with ethyl chloroformate took place. Determination was performed by gas chromatography mass spectrometry with selected ion monitoring. Ketobemidone and norketobemidone could be detected in plasma in a concentration of 1 ng ml-1 and 3 ng ml-1, respectively. Determinations were performed down to 5 ng ml-1. The relative standard deviation of the method in the analysis of 10 ng ml-1 of ketobemidone and norketobemidone, respectively, was 8% and 9% (n=10). The absolute recovery of unconjugated ketobemidone and norketobemidone through the method at the 100 ng ml-1 level was 91% and 85%, respectively. The method was applied to the determination of ketobemidone and norketobemidone in plasma from patients given ketobemidone. The concentrations of unconjugated norketobemidone was too small to be detected.

Analysis of nicotine as a trichloroethyl carbamate by gas chromatography with electron-capture detection.

Nicotine was subjected to reaction at 90 degrees with trichloroethyl chloroformate in the presence of pyridine to form a carbamate in which the pyrrolidine ring was opened. Upon heat treatment, this carbamate partially formed the corresponding olefin. About 10 pg could be detected with an electron-capture detector and 60 pg with an alkali flame-ionization detector. The extraction was studied with 14C-labelled nicotine. Methylene chloride was suitable for extraction from diluted plasma, whereas toluene containing 5% of heptafluorobutanol was used in a re-extraction step and also as the chloroformate reaction medium. Due to a nicotine blank the limit for quantitative determinations was 10 ng/ml in plasma (sample volume 1 ml). N-n-Propylnornicotine was used as an internal standard. The precision at the 30 ng/ml level was +/- 8.8% (n = 7).