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Biomedical subjects

C Caramella

Publications and source records attributed to C Caramella.

At least 37 records · Page 2Linked to original sources
PubMed1993

In vitro/in vivo correlation of prolonged release dosage forms containing diltiazem HCI.

Six preparations were considered: three multiple unit dosage forms (micropellets in capsules) (D, E and G) and one matrix tablet (B) were experimental prolonged release formulations, two non-disintegrating tablets (A and C) were commercial products. The in vitro dissolution behaviour of the differing formulations was investigated using the USP XXII paddle apparatus. The in vivo study was effected on a panel of 12 healthy volunteers. The two commercial tablets (A and C) showed mean dissolution time (MDT) of 1.34 and 1.44 h and td of 91 and 92 min, respectively; for prolonged release formulations (B, E, D, and G) MDT ranged between 2.28 and 4.23 h and td between 149 and 291 min. The mean residence time (MRT) was 8.68 and 6.47 h for tablets A and C, respectively; it ranged between 9.62 and 10.24 h for the multiple unit formulations E, D, and G and was 11.27 h for matrix B. Formulation B also showed the higher apparent elimination half-life t1/2 (7.12 h), while apparent t1/2 for all the other formulations were very similar, ranging between 5.04 and 5.28 h. High variability between the various formulations was found for Cmax and AUC values, and no relationships could be established with the type of formulation. An in vitro/in vivo correlation was found for all the formulations examined on the basis of analogous parameters (MDT and MRT); (r = 0.83, p < 0.05). In a few cases the Wagner-Nelson deconvolution method was applied to individual plasma level versus time curves and the corresponding absorption curves were obtained. In these cases the in vitro/in vivo correlation was tested on the basis of the comparison of the in vivo absorption curves with the in vitro dissolution profiles. This was accomplished using the 'Levy's plot' (per cent released versus per cent absorbed) approach and provided further support for the correlation found.

Adult↗
PubMed1992

Thiamin contents of cerebrospinal fluid, plasma and erythrocytes in cerebellar ataxias.

Free thiamin and thiamin monophosphate have been found in the cerebrospinal fluid, plasma and in erythrocytes of patients suffering from ataxia of different origins. In erythrocytes, thiamin pyrophosphate was also measured. In a limited number of cases, uptake of 14C-thiamin by erythrocytes was found as well. Controls were hospitalized patients affected by chronic neurological diseases without any clinical sign of thiamin deficiency. The results showed a significant decrease in thiamin and thiamin monophosphate in the cerebrospinal fluid and in the plasma of ataxic subjects, in comparison to controls. In erythrocytes, only thiamin pyrophosphate levels had decreased. The uptake of 14C-thiamin by erythrocytes was similar in both ataxic and control groups. These results were comparable to those observed in thiamin-deficient individuals, like alcoholic patients, and prompted further investigation into thiamin metabolism in these diseases.

Adult↗
PubMed1991

A computer-aided simulation approach in the development of a prolonged release formulation.

Prolonged medication with diltiazem has proved advantageous in the treatment of coronary insufficiency and arterial hypertension. Consistently, a number of extended release formulations, based on different retardation mechanisms, have been proposed. In the present work two prolonged release oral formulations containing diltiazem, one intended for twice-a-day and one for once-a-day administration, were tested for in vitro behaviour; the in vitro release test had been opportunely validated using an in vitro-in vivo correlation approach. On the basis of in vitro release profiles, simulations were effected, using a computer program previously developed, in order to generate the plasma levels that could be expected on single dosing of the two formulations. The two formulations were then tested in vivo and the measured plasma profiles were compared with those predicted from in vitro data. For both formulations, a good agreement was found between the measured and the simulated plasma levels, thus demonstrating the usefulness of the simulation approach in the formulative development.

Adult↗
PubMed1989

Rheological properties and diffusion dissolution behaviour of hydrophilic polymers.

In a mathematical model that has been recently proposed to predict drug release from polyvinyl alcohol matrices, polymer dissolution is described as a chain disentanglement process and characterized by a threshold polymer concentration. In present work viscosity measurements were employed for defining the characteristic entanglement concentration of polymer solutions. The viscosity of aqueous polymer solutions of differing concentrations was measured over a wide range of shear rate using a rotational viscometer. The flow curves were fitted according to an asymptotic model and from the best fit equation the relevant viscosity parameters were obtained. The relationships between polymer concentration and viscosity parameters were also examined. The critical concentration at which an abrupt change of viscosity properties occurred was identified and related to the molecular chain disentanglement conditions.

Chemical Phenomena↗
PubMed1989

Swelling-restricted minimatrices for controlled release of drugs. Preliminary in-vivo studies.

A preliminary in-vivo study was performed on a new modified release system which contained diltiazem hydrochloride. The system consisted of swellable minimatrices that were coated with an acrylic polymeric film. The film thickness, because of its pH-dependent solubility, might represent a critical variable with regard to in-vivo release. In order to evaluate the influence of such a variable on in-vivo behaviour, two minimatrices formulations with differing film thickness were tested versus a commercial tablet. The in-vivo study, which was based on a balanced incomplete block design, involved six volunteers in two sequences. The drug was quantified in plasma by an HPLC method. Computation and statistical analysis of pharmacokinetic parameters were performed by means of SIPHARR package (Simed, F). The results show that the approach of film coating, in order to modify the release rate from minimatrices, is feasible, but it must be improved; in particular the results point to the necessity of reducing the film susceptibility to pH changes.

Adult↗
PubMed1984

Disintegrating force as a new formulation parameter.

Some coated aspirin tablet formulations were evaluated by relating their properties to disintegrating force development patterns. The treatment of disintegrating force-time curves was effected using the Weibull distribution as proposed for dissolution. Such parameters as the maximum disintegrating force developed, the time needed to reach 63.2% maximum disintegrating force (tau d) the shape parameter, the lag time, and the input value were used for evaluating the formulas examined. It was concluded that the input values, the integrating force development rate at tau d, can be employed as a new formulation parameter since, when correlated with the crushing strength, it allows an overall evaluation of the formula examined.

Aspirin↗