Sci. Pharm., Volume 72, Issue 4 (December 2004) – 6 articles

The impact of variations in the wet granulation step during the manufacturing process on the in-vitro and in-vivo performance of ibuprofen sustained release matrix tablets was investigated. Two batches were produced under different wet granulation conditions. The granules of the first batch (T1) were characterized by having a lower bulk density (0.56 g/ml), a higher percentage of fines (56.7% w/w) and a smaller geometric mean diameter (dg), 600 µm. While the granules of batch (T2) were characterized by having a more coherent properties, a higher bulk density (0.66 g/ml), a lower percentage of fines (36.9% w/w) and a larger dg, 720 µm. Three large scale production batches (B1, B2, B3) were manufactured similarly to T2 and found to have granules possessing similar properties. In-vitro tests showed that tablets of T1 had a statistically significant higher release rate constant than tablets of either T2, B1 ,B2 or B3. In-vivo tests were done using T1 and T2 tablets. Although T1 and T2 were bioequivalent with respect to Cmax and AUC, T2 exhibited a statistically significant longer sustained release characteristics than T1 (P<0.05). Full article

In certain situations of peptic ulcers ampicillin has been co-administered with bismuth carbonate with an implication for adsorption of the ampicillin. To quantify this effect the kinetics and extent of adsorption of ampicillin by some commonly used antacids were measured; these are bismuth carbonate, magnesium trisilicate and aluminium hydroxide. The adsorption of ampicillin by bismuth carbonate followed the Langmuir adsorption isotherm, which suggests chemisorptions. It was characterized by a strong adsorption at a low adsorbate (ampicillin) concentration but the % adsorption decreased with increase in adsorbate concentration, which is a feature of a saturated monolayer adsorption. On the other hand, the adsorption by magnesium trisilicate and aluminium hydroxide followed the Freundlich adsorption isotherm characterized by a low adsorption at a low adsobate concentration but this increased slightly with increase in adsorbate concentration, suggesting a weak physical adsorption. The adsorption capacities (mg/g) of the adsorbate were 1.64 (bismuth carbonate) 0.04 (magnesium carbonate) and 0.03 (aluminium hydroxide). Bismuth carbonate thus gave by far the highest degree of adsorption. The conclusion is that the co-administration of ampicillin and bismuth carbonate in the treatment of certain peptic ulcers is erroneous. Full article

The spheres were prepared by the desolvation technique combined with gravitational sedimentation of droplets of methylcellulose gel suspensions with the addition of 25% quinidine adsorbate on the potato starch and 5% hydrophilic agents such as Span 80, Tween 60, glyceryl monostearate or PEG 2000 instilled into a desolvation liquid (saturated sodium acetate:paraffin liquid:heptane 1:1:1, v/v/v) through a standardized capillary.As follows from the physicochemical studies the sphericity (Sp) changed within the range 1.020–1.314, the porosity (P) was 19.1–66.5% and the loading efficiency was 35.10–67.07%. The release studies show that the dissolution efficiency after 60 min (DE₆₀) in acidic medium was 78.6% for quinidine and 52.6–63.4% for the spheres; in phosphate buffer pH 6.8 DE₆₀ was 32.4% for quinidine, but ranged within 16.3–26.0% for the spheres. The release of the drug from the spheres was fast and it was slightly difference (the loaded drug was released within 60 min) in acidic medium, while differentation of release in the phosphate buffer made it possible to evaluate the effect of hydrophilic additives on the dissolution rate.The general process of release can be described by the modified Higuchi equation $M_t^{*}=K_0·(\sqrt{t}-\sqrt{T_D})$ , which facilitates the analysis of the theoretical amount of the released substance $M_t^{*}$ depending on the zero-order dissolution rate constant K₀ and the dissolution lag time (T_D). Accordingly, spheres with sustained release can be most effectively produced by addition of PEG 2000. These spheres are characterized by Sp = 1.035, P = 60.2% and a loading efficiency of quinidine 67.07%. The release in acidic medium proceeds with K₀ = 3.857 mg·min^−0.5 and T_D = 6.21 min, in phosphate buffer K₀ was 1.293 rng·min^−0.5 and T_D = 7.14 min. These parameters were of less importance for the other formulations. The modified Higuchi equation gives information about the parameters of drug released. Full article

1-(4-fluoropheny1)-4-[3-(2-,3- and 4-alkyloxyphenylcarbamoyloxy)-2-hydroxypropyl]piperaziniumchlorides, with one to four carbon atoms in the alkoxy group on aromatic ring have been synthesized as the derivatives of substituted phenylcarbamic acid. The structures were confirmed by their spectral data. Potential antiarrhythmic activity was evaluated in guinea-pigs model. Preliminary studies demonstrated that the evaluated compounds, using ouabain arrhythmia model, appear to possess only moderate antiarrhythmic activity. Only compound marked as 4f appears to be more potent and lead us to focus our attention on structures with more bulky substituent in the m-position at aromatic ring in the hydrophilic part of molecule. Full article

All trans retinoic acid (RA), derived from the oxidative metabolism of dietary retinol (vitamin A) and β carotene, contributes to the growth and differentiation of mammalian epithelial tissues. RA is rapidly cleared from the plasma and sudenly metabolized in tissues. The increase of its biological potency through inhibition of its oxidative metabolism is consistent with this.This research is part of a study to develop novel compounds as inhibitors of retinoic acid metabolism that could have potential value as anticancer agent. The investigation was done to compare the in vitro metabolism of [³H]RA by hepatic m icrosomes from several common laboratory animal species. Also, the ability of ketaconazole to inhibit RA metabolism was examined. The species studied were male rat, male New Zealand white rabbit, male albino mouse, male Syrian hamster, male Dunkin hartley guinea pig and male nude mouse. The results revealed that km and Vmax were species dependent. Among the animals, rat liver appeared to be the most active in metabolizing RA. Inhibition of RA metbolism by ketoconazole (100 µM) was very similar in the hepatic microsomes of all the species examine. Overall the results indicate that male rat hepatic microsomes represent a useful enzyme source for screening novel compounds as inhibitors of RA metabolism. Full article