Capping Tendency Research Articles

The Role of Several l-HPCs in Preventing Tablet Capping During Direct Compression of Metronidazole

Several low-hydroxypropyl cellulose (l-HPC) derivatives (LH-11, 21, 22, 31, and 32) differing in granulometric particle size or in hydroxypropyl content were considered in the present study. The l-HPC grades were characterized as pure powders, in order to determine both compression and densification behavior, in presence or in absence of magnesium stearate as lubricant, and then, were physically mixed in different proportions with metronidazole, which was also previously characterized as pure powder. The tabletability and compressibility of these binary mixtures were then evaluated, in presence or in absence magnesium stearate as lubricant at two different compression speeds (20 and 70 mm/sec). It was observed that both binary mixture compression behavior and capping tendency were influenced by compression speed and by the presence of lubricant.Differences in anti-capping efficiency between the l-HPCs may be related to their hydroxypropyl content. This parameter influences the interaction between the metronidazole and the polymer particles, and consequently the ability of the binary system to undergo densification under compression.

Evaluation of the binder effects of the gum mucilages of Cissus populnea and Acassia senegal on the mechanical properties of paracetamol tablets

A comparative study has been carried out to investigate the binder effects of the gums of Cissus populnea and Accasia senegal on the mechanical properties of paracetamol tablets. Tablet mechanical properties evaluated include the packing fraction (Pf), the tensile strength (T) and the brittle fracture tendency (BFI). Varying concentrations of the gum mucilage ranging from 1 - 15% (w/v) was prepared and their relative viscosities determined. Each concentration was used to wet massed paracetamol powder to form granules. Tablets of paracetamol (500 ± 6.5 mg) were compressed at a constant compression load (7 arbitruary units on the scale). The tablets were equilibrated for 24 h before evaluation. At all binder concentrations A. senegal gum produced harder and more consolidated tablets than C. populnea as reflected by the higher T and Pf values respectively. For instance, the T and Pf values of the tablets at binder concentration of 10% (w/v) were 0.69 MNm-2 and 0.47 (A. senegal) and 0.57 MNm-2 and 0.23 (C. populnea), respectively. On the contrary, an increase in binder concentration generally resulted in a decrease in BFI values and this decrease was more marked with C. populnea. The study showed that A. senegal mucilage displayed better tableting characteristics and higher tendency for ameliorating capping tendency. Both mucilages have the potentials for substitution as binder for the more expensive starches in tablet formulation.

Effects of plantain and corn starches on the mechanical and disintegration properties of paracetamol tablets

The effects of plantain starch obtained from the unripe fruit of the plant Musa paradisiaca L. (Musaceae) on the mechanical and disintegration properties of paracetamol tablets have been investigated in comparison with the effects of corn starch BP using a 2(3) factorial experimental design. The individual and combined effects of nature of starch binder (N), concentration of starch binder (C), and the relative density of tablet (RD) on the tensile strength (TS), brittle fracture index (BFI), and disintegration time (DT) of the tablets were investigated. The ranking of the individual effects on TS was RD > C >> N, on BFI was C >> RD > N and on DT was N > C > RD. The ranking for the interaction effects on TS and DT was N-C >> N-RD > C-RD, while that on BFI was N-C >> C-RD > N-RD. Changing nature of starch from a "low" (plantain starch) to a "high" (corn starch) level, increasing the concentration of starch binding agent from 2.5% to 10.0% wt/wt, and increasing relative density of the tablet from 0.80 to 0.90, led to increase in the values of TS and DT, but a decrease in BFI. Thus, tablets containing plantain starch had lower tensile strength and disintegration time values than those containing corn starch, but showed better ability to reduce the lamination and capping tendency in paracetamol tablet formulation. The interaction between N and C was significantly (P < .001) higher than those between N and RD and between C and RD. There is therefore the need to carefully choose the nature (N) and concentration (C) of starch used as binding agent in tablet formulations to obtain tablets of desired bond strength and disintegration properties. Furthermore, plantain starch could be useful as an alternative binding agent to cornstarch, especially where faster disintegration is required and the problems of lamination and capping are of particular concern.

Effect of lubrication on the compaction properties of pharmaceutical excipients as measured by die wall pressure

The effects of lubrication on the compaction properties of pharmaceutical powders were evaluated by measuring several compaction parameters, including maximum die wall pressure (MDP), residual die wall pressure (RDP), and RDP/MDP, which is a novel parameter for evaluating the compaction properties of materials. In tableting model powders lactose and mannitol, a higher RDP/MDP and a tendency toward capping were observed. The addition of a small amount of internal lubricant to either powder decreased RDP/MDP and inhibited the capping tendency. When external lubrication was applied to the powders, similar improvements in these compaction properties were observed. However, the tensile strength of the mannitol tablet prepared under external lubrication conditions was much greater than that of the tablet prepared with 0.5% internal lubricant. On the other hand, the hardness of lactose tablets was almost the same irrespective of the lubricating method. These phenomena were explained by the plastic deformation property of mannitol and by the fragmentation of lactose particles during compression.

Investigations into the stabilisation of drugs by sugar glasses: I. Tablets prepared from stabilised alkaline phosphatase

The aim of this study was to investigate the formulation of sugar glass stabilised alkaline phosphatase from bovine intestine (BIAP) into tablets. Two major subjects of tablet formulation were investigated. First, the compaction behaviour of the inulin sugar glass was investigated. Secondly, the effect of the compaction process on the physical stability of sugar glass stabilised BIAP was investigated, comparing inulin and trehalose glass. The tabletting properties of freeze-dried inulin without BIAP were studied first. Freeze-dried inulin conditioned at either 20 °C/0% relative humidity (RH) or 20 °C/45% RH was compacted at various pressures. As expected, the yield pressure of the material conditioned at 0% RH was higher (68 MPa) than after conditioning at 45% RH (39 MPa). Tablets made of the material stored at 0% RH showed severe capping tendency, especially at high compaction pressures. In contrast, material conditioned at 45% RH gave tablets without any capping tendency and a friability of less than 1%. Sugar glasses of BIAP and either inulin or trehalose were prepared by freeze-drying (BIAP/sugar 1/19 (w/w)). The material was subsequently compacted. Tablets and powders were stored at 60 °C/0% RH. The activity of the incorporated BIAP was measured at various time intervals. It was found that inulin was by far superior to trehalose as stabiliser of BIAP in tablets. The poor stabilising capacities of trehalose after compaction are explained by crystallisation of trehalose induced by the compaction process and moisture in the material. The results clearly show that inulin is an excellent stabiliser for BIAP. The tabletting properties are adequate, showing sufficient tablet strengths and low friability. Furthermore, the good (physical) stability of inulin glass with respect to exposure to high relative humidities makes it practical to work with.

An investigation into the capping of paracetamol at increasing speeds of compression

Abstract A study of the capping tendency of paracetamol using a wide range of compression speeds (24–850 mm/s) has been performed. Capping pressure, plastic energy (PE) and elastic energy (EE), EE/PE ratio, work of compaction and mean yield pressure derived from Heckel analysis were used as the basis of the investigation. The capping intensity of paracetamol was observed to increase with an increase in the speed of compression, due to the significant increase of 65.24% in the elastic energy compared to a 32.87% increase in plastic energy over the same speed range. The relatively high increase in elastic energy appears to be a more important factor than air entrapment in the capping tendency of paracetamol compacts. The work of compaction was found to increase with compression speed, ascribed to a high energy input required for elastic deformation, fragmentation of particles and formation of bonds. A good correlation was observed between the natural logarithm of compression speed and capping pressure and an equation has been proposed to describe the relationship. The critical excipient content was found to be 25% and 50% w/w of microcrystalline cellulose (MCC) at a speed of 24–300 mm/s and 500 mm/s, respectively, however incorporation of 25% dibasic calcium phosphate dihydrate (DCP)/75% w/w microcrystalline cellulose (MCC) in paracetamol formulations was found to have greater resistance to capping and produced tablets with double the tensile strength of compacts containing 25% w/w of MCC alone.

Application of a newly defined capping index in evaluation of the compressibility of pharmaceutical powders

The compressibility of pharmaceutical powders was evaluated using the capping index which was newly defined as the ratio of the residual die wall pressure to the binding strength of compacts. As the compaction pressure was increased, the residual die wall pressure increased while the binding strength reached a plateau, and the resultant capping index increased. These facts explained the capping behaviors during tableting under various compaction pressures. In the case of a binary powder mixture, the residual die wall pressure changed in a simple manner with a change in powder composition while the binding strength changed in a complex manner. It was found that the capping tendency of these mixtures could be correlated with the capping index. It was also found that the addition of polymeric powders was effective to prevent capping.

Characterization of die wall pressure to predict capping of flat- or convex-faced drug tablets of various sizes

Die wall pressure during compaction of drug powders was measured to elucidate the mechanisms involved in capping. More than 200 kg/cm 2 of die wall pressure remained after decompression, whereas in the case of capping, the die wall pressure rapidly dropped at the final stage of the decompression process. These results suggested that capping was the fracture of compacted powders caused by high residual die wall pressure. The extrapolated residual die wall pressure of convex-faced tablets was higher than that of flat-faced ones. For the convex-faced tablets, the thinner ones indicated a higher residual die wall pressure. These results coincided with the capping tendency seen in drug tablets and should pave the way for a better design of tablet formulation.

Influence of substance properties on scaling up of tablet formulations

The influence of water content of furosemide in a direct compressible tablet formulation was studied in pilot plant production. Small variations in the water content of furosemide as determined by thermogravimetry was found to have a substantial influence on the compaction properties of the direct compressible formulation.A study of furosemide per se revealed that an increase in water content from 0.06% to 0.24% resulted in an increased elastic recovery and decreased net work at compaction. By adjusting the water content of furosemide in the direct compressible formulation it was possible to avoid the capping tendency at tablets.

残留壁面圧と結合強度による粉末の圧縮成形性の評価

The compressibility of powders was evaluated by using residual die wall pressure and measuring the binding strength of the compacted powders.The binding strength was reflected in a saturated curve as the compaction pressure increased. However, the residual die wall pressure increased in proportion to the compaction pressure. These phenomena explained the capping behaviors during tableting.In the binary mixed powders, the binding strength changed in a complicated way, but the residual die wall pressure changed simply with the composition of the mixture. The ratio of these two values was defined as the capping index, and the actual capping tendency was defined as the capping ratio. Good correlation was observed between this index and ratio.

Formulation effects on capping tendencies

Formulation effects on capping tendencies

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.

Ruling Factors of Capping in the Compressing Process and the Method of Preventing Capping

The production of compressed materials, such as tablets, is often jeopadized by capping. Special phenomenalistic studies were made of the factors of capping, and the method to prevent capping was devised.Using a tableting machine and a compression testing instrument, the capping tendency under various compressing and ejecting conditions was studied. As the result of the investigation the following conclusion was reached. Capping occurs mainly within the range of about 3mm from the starting point of ejection. Application of suitable pressure within that range is effective for prevention of capping, and the magnitude of pressure is calculated from the quantity of the wall friction between the compressed material and the die in the ejecting process.

Evaluation of the Physical Properties of Compressed Tablets I: Tablet Hardness and Friability

Studies were conducted to evaluate what changes occurred in the physical properties of compressed tablets as the operation of a rotary tableting machine was varied. Thin large-diameter tablets showed a capping tendency that was not apparent in smaller-diameter or thicker tablets. The crushing strength of tablets stored at 71 per cent R.H. for 28 days was unchanged, but the tablets became more friable. Increasing the compressional speed reduced the crushing strength and increased the capping tendency, but did not affect the friability of compressed tablets. At the higher compressional rates, the tablets showed a greater elastic response than at the slower speeds. Compressing the tablets at various depths in the die had no affect on the physical properties of the compressed tablets.