Dissolution and spectrophotometric determination of astaxanthin in aqueous solutions.

The poor solubility of astaxanthin in water can cause problems during dissolution tests of dosage forms because they are usually performed in water-based media. The aim of this study was the development of a convenient dissolution medium and a method for a spectrophotometric determination of astaxanthin in an aqueous solution. Three surfactants in different concentrations were tested as solubility-improving substances: sodium lauryl sulfate (SLS), polysorbate 80 (PS 80) and macrogolglycerol hydroxystearate (Cremophor RH 40, CR 40). Optimal conditions were determined. The dissolution of astaxanthin from solid dosage form is performed into 1000 g of a solution of sodium lauryl sulfate with the concentration 1.0% (w/w) at 37 degrees C by paddle method, 100 rotations per minute, dissolution time 30 minutes. The procedure is convenient for solid dosage forms with a content of 4 to 12 mg of astaxanthin. The spectrophotometric determination of astaxanthin in aqueous solution from the dissolution test is measured at 486 nm. The specific absorbance A(1%) 1cm for astaxanthin in water is 2000, a sodium lauryl sulfate solution (1%) was used as a blank.

[Effect of pharmaceutical aids on physico-chemical indicators in solutions of substance XXII B]. / Vplyv pomocných látok na fyzikálno-chemické ukazovatele roztokov látky XXII B.

Within a study of optimization of auxiliary substances in the formulation of a hydrogel containing a potential local anaesthetic agent, substance XXII B, the paper evaluated the effect of a preservative (Ajatin) and humectants (glycerol, propylene glycol, sorbitol) on selected physicochemical indices, which included the partition coefficient, surface tension, and viscosity of the solutions of potential drug XXII B. On the basis of the statistical evaluation of the results, the optimal combination of auxiliary substances in this case seems to be Ajatin + glycerol.

Influence of hydrogel bases on liberation rate and structural viscosity of potential drug XX Z.

Influences of cellulose derivatives (with and without additives of humectants) on two parameters, namely the liberation of the potential local anaesthetic XX Z and the structural viscosity of preparations were compared. The aim was to select a suitable base for topic application of the substance XX Z, chemically pyrrolidinoethylester of 3-heptyloxyphenylcarbamic acid. The rate of release of the substance XX Z from 2.5% methylcellulose base was higher then from 2% hydroxyethylcellulose base, and in both cases it was reduced after addition of humectants. It is concluded that among bases with additives of humectants is, for topic applications, more suitable the hydroxyethylcellulose base then methylcellulose base.

A study of local anaesthetics. Part 148. Influence of auxiliary substances on the surface tension, distribution coefficient and pharmaceutical availability from solutions of the potential drug VII.

The influence of auxiliary substances of the polyol group (glycerol, propylene glycol, sorbitol) and of their concentration (5, 10, 15 and 20% by weight) upon surface tension, distribution coefficient and pharmaceutical availability from solutions of the potential drug VII, viz., N-[2-(2-propoxyphenylcarbamoyloxy)-ethyl] piperidinium chloride was studied. The substances were applied as hydrogel humectants. It was found that their influence on the surface tension, distribution coefficient and pharmaceutical availability from solutions of the potential drug VII depended on the type as well as concentration of the auxiliary substance. From the viewpoints of use in formulations of the drug form, sorbitol used at 5 and 10% concentrations represented the optimum.

Study of local anaesthetics. Part 139. Preformulation study of N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl] dimethylammonium chloride.

In the course of the drug form development of substance XIX B (N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl] dimethylammonium chloride [1]) the influence of auxiliary substance, namely glycerol (GL), propylene glycol (PG) and sorbitol (SO), used in the form of 5, 10, 15 and 20% solution, on the surface tension, partition coefficient, viscosity and liberation from aqueous solutions was studied. These parameters can influence the bioavailability. The obtained results show that as an optimal additive 5% SO may be used since this ensured maximal amount of liberated substance XIX B.

Influence of auxiliary substances on the release of heptacaine from the drug form.

In the course of the drug form development of heptacaine potential local anaesthetic, the influence of auxiliary substances on the heptacaine release and its local anaesthetic effect was studied. The obtained results show that the following auxiliary substances are optimal: a) 0.3-1.2% solution hydroxypropylmethyl cellulose for 0.025% eye drops, which have the fastest onset of the local anaesthetic effect in the hamster's eye, b) hydroxyethyl cellulose containing 0.5% heptacaine and 10% glycerol or propylene glycol for hydrogels, c) cocoa oil without and with Dimodan S for suppositories.

Study of local anaesthetics. Part 136. Influence of auxiliary substances on the release of pentacaine from drug forms.

The paper deals with the formulation of a potential local anaesthetic--pentacaine into appropriate drug forms. To be more specific, the pentacaine is studies from the two aspects. First, the influence of auxiliary substances and their respective concentrations on the both onset and duration of local anaesthetic effects of pentacaine solutions. Second, the liberation of pentacaine from hydrogels and suppositories. Based on the obtained results, optimal auxiliary substances together with their optimal concentration are recommended.

The influence of glycerol, propylene glycol and sorbitol on surface tension, partition coefficient and diffusion of pyrrolidinoethylester of 3-heptyloxy phenylcarbamic acid (drug XX Z).

The influence of glycerol, propylene glycol and sorbitol on surface tension, partition coefficient and diffusion of pyrrolidinoethylester of 3-heptyloxy phenylcarbamic acid (Drug XX Z) from solutions has been studied. It was found that each of the three mentioned auxiliary substances causes, proportionally to its concentration (5, 10, 15 and 20%), the increase of the surface tension and the decrease of the partition coefficient. A correlation between the surface tension and partition coefficient was proved. The diffusion of the drug XX Z was increased due to use of the auxiliary substances. With respect to these results and in accordance with the rules for development of the drug form, sorbitol in concentration 5-10% seems to be an optimal auxiliary substance.

Study of the influence of the auxiliary substances on the surface tension of the aqueous solutions of some substituted phenylcarbamic acid derivatives.

In the course of the drug form development of potential drugs the influence of auxiliary substances, namely glycerol (GL), propylene glycol (PG) and sorbitol (SO), used in the form of 5, 10, 15 and 20% solution on the surface tension (gamma) of some phenylcarbamic acid aqueous solutions was studied. Since this influence depends not only on the kind and concentration of the auxiliary substance used but also on potential drugs themselves, attempt was made to find optimal additives for particular drugs. The obtained results show that as optimal additives may be used: SO for IR-1 and H + B, for XIX M it is either PG or GL, for XIII it is GL, and finally for XIX it is either PG or SO.

Study of local anaesthetics: Part 124. Influence of the ointment bases on the liberation of pentacaine chloride and heptacaine chloride.

The aim of the study was to choose a suitable base for the topical application of pentacaine chloride and heptacaine chloride. Both local anaesthetics were processed into two hydrophilic creams, two hydrophobic creams and one hydrophobic ointment as well as into three hydrogel bases. The assumption that the rate of the release of both local anaesthetics from hydrogel bases is greater than from cream bases has been fully confirmed.

Study of the influence of auxiliary substances on the partition coefficients of some substituted phenylcarbamic acid derivatives.

In the course of the drug form development of newly synthetized potential drugs the influence of the auxiliary substances, glycerol (GL), propylene glycol (PG), and sorbitol (SO) in concentration of 5, 10, 15 and 20%, on the partition coefficient (P') of some phenylcarbamic acid derivatives was studied. Because of the great variations of this influence, attempts were made to find optimal additive for the further processing. The obtained values of P' show that an optimal additive for the drug H+B seems to be SO while in the case of the substances XIX M and XIX the optimal additives are PG or GL and SO, respectively.