Effects of tapioca obtained from cassava (Manihot utilissima) on the disintegration and dissolution rates of paracetamol tablets.

The properties of tapioca obtained from cassava (Manihot utilissima) have been evaluated. Its binding effect in tablets of paracetamol on the disintegration and dissolution rates was compared with tablets prepared with polyvinylpyrrolidone and gelatin. The nature and amount of the binders were found to alter the disintegration and dissolution rates of the tablets by reducing their wettability as measured by the adhesion tension of water. A linear relationship has been found to exist between the adhesion of water on the tablets and their disintegration and dissolution rates.

The effects of interacting variables on the tensile strength, disintegration and dissolution of paracetamol tablets.

A factorially designed scheme has been used to analyse the separate and combined effects of packing fraction (P), nature of binder (N) and concentration of binder (C) on the tensile strength, disintegration and dissolution (t50%) times of paracetamol tablets. In general, P has the greatest effect on tensile strength, disintegration and dissolution times followed by C then N. For the variables in combination, the ranking of the effects on tensile strength, for the PVP/gelatin formulations, are P x N greater than N x C greater than P x C and for the PVP/tapioca formulations are P x C = N x C greater than P x N. For disintegration and for dissolution, the ranking for the PVP/gelatin formulations are P x C greater than P x N = N x C and P x N greater than P x C greater than N x C, respectively, and for the PVP/tapioca formulations are P x N greater than N x C = P x C. The results also show that tapioca acts as a binding agent when included in paracetamol tablet formulations, but it is a weaker binder than either PVP or gelatin. It is thus required in a higher concentration to produce tablets of comparable physical properties with those formulated with PVP or gelatin.

Effects of applied load and particle size on the plastoelasticity and tablet strength of some directly compressible powders.

Correlations have been established between the particle size and packing fraction of microcrystalline cellulose, calcium phosphate dihydrate, corn starch and lactose, and the elastic recovery, stress relaxation, and tensile strengths of their tablets.

The effect of temperature on the plasto-elasticity of some pharmaceutical powders and on the tensile strengths of their tablets.

Measurements have been made of the stress relaxation (SR) during, and of the elastic recovery (ER) after, compression of four directly compressible excipients, and of chloroquine diphosphate and of a paracetamol tablet formulation at temperatures between -10 and +65 degrees C and of the tensile strengths of the tablets produced. It was found that at a fixed packing fraction, the stress relaxation and tensile strength of all the materials increased and the ratio ER/SR decreased as the compression temperature was raised. Tensile strength was inversely proportional to ER/SR at all the temperatures studied. Values for the activation energies (Eo) of bonding between particles for all the materials were derived from plots of the log of tensile strength and of log SR/ER versus the reciprocal of the absolute temperature. The values of Eo obtained from the latter plots tended to be higher than from the former by a factor of between 1.5 and 4.5.

The plasto-elasticity and compressibility of coated powders and the tensile strengths of their tablets.

A study has been made of the effects produced on the tensile strength, brittle fracture index (BFI), 'plasto-elasticity' ratio, ER/PC, and yield pressure (1/KH derived from Heckel plots) of sodium salicylate and calcium carbonate as a result of coating their particles with increasing amounts of silicones and polysorbates before subjecting them to compression to form tablets. The coatings act as lubricants reducing bond formation due to plastic deformation of particles. They caused a reduction in the tensile strengths and yield pressures of the tablets but increased their BFI values and their ER/PC ratios. Tablets of calcium carbonate tended to cap or laminate when their BFI value was greater than 0.7 and their ER/PC ratio was greater than 7. Sodium salicylate whose BFI values were all less than 0.7 produced satisfactory tablets when their ER/PC ratio was less than 10 but tended to cap or laminate when it was greater than 10.

The effect of some excipients on the physical properties of a paracetamol tablet formulation.

The effects of the addition of the excipients sorbitol, sodium lauryl sulphate and Aerosil on the physical properties of a paracetamol tablet formulation have been evaluated. Increase in the concentration of sorbitol and sodium lauryl sulphate caused a decrease in the hardness with a corresponding increase in the friability, disintegration and dissolution rates of the tablets. The mode of incorporation of the excipient, Aerosil, greatly influenced the physical properties of the paracetamol tablets. When added internally, the tablets' strength decreased while the friability, disintegration and dissolution rates increased. However, when Aerosil was added externally, the strength of the tablets increased while their friability, disintegration and dissolution rates decreased.

The effect of temperature on the tensile strength and disintegration of paracetamol and oxytetracycline tablets.

The tensile strengths and disintegration times of paracetamol and oxytetracycline tablets at room temperature are higher when they have been prepared at high temperatures, e.g. 85 degrees, than at room temperature or below, e.g.--20 degrees. The activation energies of the two materials, 3 and 1 k cal mol-1 (13 and 4kJmol-1) respectively, were derived from plots of log tensile strength and log disintegration time versus the reciprocal of the absolute temperature. The results have been explained in terms of sintering theory and the formation of welded bonds between particles.

Formulation factors affecting strength and dissolution of uncoated oxytetracycline tablets.

The effect of various formulation and processing factors on the properties of 300-mg oxytetracycline tablets was studied. At a constant moisture level and packing fraction, an increase in gelatin concentration resulted in increased tensile strength, increased disintegration and dissolution times, and reduced capping tendency. The Wagner theory of dissolution applied satisfactorily to tablets containing up to 5% (w/w) gelatin but was less applicable at higher gelatin levels. Dissolution rate constants were calculated, and their values depended on the gelatin content and packing fraction of the tablets.

Moisture and gelatin effects on the interparticle attractive forces and the compression behaviour of oxytetracycline formulations.

The tensile strengths of compacts and/or tablets of the individual components and of granules prepared from an oxytetracycline formulation have been measured using the diametral compression test. Employing the theory of tensile strength, proposed by Cheng, it has been shown that increases in both moisture and gelatin contents of compacts and tablets increase the range of the attractive forces that operate between the granules. By studying the effects of moisture and gelatin on the compressional behaviour of the granules, it has been possible to classify them into different types. Fragmentation of granules occurs at packing fractions between 0-745 and 0-835, depending on their gelatin content.

Some formulation factors affecting the tensile strength, disintegration and dissolution of uncoated oxytetracycline tablets.

A study has been made of the effects of gelatin binding agent and moisture content on the tensile strength, disintegration and dissolution times of oxytetracycline tablets. These properties all increase with the gelatin content, and maximum tensile strengths occur when the tablets contain between 2.5 and 4.5% w/w of moisture. The properties of the tablets depend on their packing fraction and in general, the disintegration and dissolution times are minimal when the packing fraction is between 0.77 and 0.82. A connection has been established between the disintegration times of the tablets and the time required for 50% of the drug content to dissolve.