Behavior Of Tablets Research Articles

DISSOLUTION BEHAVIOUR OF METRONIDAZOLE TABLETS

The dissolution behavior of metronidazol tablets from three locally manufactured brands on the Egyptian market was studied. Four batches from each brand were collected from the market. The compliance of the tablets collected to the USP XX requirements was evaluated. Some batches from certain brands sis not pass the USP XX requirements for disintegration time, potency and weight variation. The USP XX paddle method was used for the dissolution studies. 0.1 N HCl at 37°C was used as the dissolution medium. Nine tablets from each batch were considered in the dissolution study. The results revealed significant differences among and within the batches of the same brand for the percent metronisazole dissolved after 10, 30 and 105 minutes at p£ 0.1 significance level. Moreover a significant difference was found to exist between different brands. The dissolution rate of drug powder was found to be higher than that of tablets. Furthermore, the drug powder filled into capsules showed higher dissolution behaviour than tablets and lesser than drug powder. In addition, the bioavailability of the drug powder filled into capsules as well as tablets, was studied. The results revealed that there was a correlation between the in-vitro dissolution rate of the drug and its in-vivo absorption data.

Effect of storage on crushing strength, disintegration and drug release from mixed tablet bases

Several studies have been reported (Horhota et al., 1976; Lausier et al., 1977; Chowhan and Palagyi, 1978; Molokhia et al., 1982) on the changes in behavior of tablets upon storage. Such changes were found to be responsible for some bioavailability problems (York, 1977; Gouda et al., 1980). In a previous communication (Molokhia et al., 1982), the effect of two storage conditions 5O”C/50% relative humidity (R.H.) and 40 ‘C/90% R.H. on crushing strength, disintegration and drug release from single component tablet bases were reported. While lactose-, mannitoland sorbitol-based tablets were subjected to significant physical changes, tricalcium phosphate and powdered cellulose-based tablets were resistant to changes over a period up to 53 days. In this study, binary blends of the previously used tablet bases were incorporated with 25% benzoic acid, 4% starch, 2% talc and 1% magnesium stearate. Mixing was carried for 10 min in a tumbling mixer rotating at 60 rpm. The product was then compressed into tablets and examined for the effect of storage at 40 o C/90% R.H. on crushing strength, disintegration and drug release. The tablets, stored in paper bags, were examined at different time intervals over 10 weeks. The crushing strength and disintegration were determined as before (Molokhia et al., 1982). The drug release was determined by following the amount of benzoic acid dissolved as function of time using a USP dissolution apparatus and phosphate buffer 0.05 M, pH 6.0, as solvent. Samples were taken every 5 min for 35 min, filtered through 0.45 pm Millipore filter and assayed by measuring UV absorption at 222 nm. Fig. 1 shows the effect of storage on the crushing strength of tablets made of lactose and tricalcium phosphate. Similar graphs were obtained for each group of

Unloading and Postcompression Viscoelastic Stress versus Strain Behavior of Pharmaceutical Solids

□ The viscoelastic properties of several compacts composed of drugs and direct compression excipients have been measured during the stress unloading and postcompression phases of the tablet compression process. Measurements of applied strains and the resultant stresses, generated in the tablet structure under compaction, were made using a rotary press. The press was instrumented to measure punch and die wall stresses at normal operating speeds. The three-dimensional viscoelastic theory, used in data analysis, provides for the separate characterization of tablet behavior into its dilation and distortion components. The tablets investigated were found to behave elastically in dilation, but to have both viscous and elastic contributions to their stress/strain relaxation in distortion. This latter behavior could be modeled well as a Kelvin solid. Data derived from an elastic-in-dilation, Kelvin-in-distortion analysis of tablets, compressed at similar machine speeds hut at various peak pressures, were found to vary widely depending on tablet composition. Dependence of the viscous and elastic parameters on compression conditions was found to be predictive of conditions under which capping or lamination of the compact would occur.

Viscoelastic Stress/Strain Behavior of Pharmaceutical Tablets: Analysis during Unloading and Postcompression Periods

The processes of nonequilibrium generation and decay of axial and radial stresses within tablet compacts were analyzed in terms of three-dimensional linear viscoelastic theory. A rotary tablet press was instrumented to measure punch and die wall stresses during the compression and postcompression periods. Following compression, tablets were permitted to remain at the compression site within the die, and the die wall stress was followed. Microcrystalline cellulose, spray-processed lactose, and sulfacetamide are known to have different compression characteristics and were found to differ significantly in their viscoelastic parameters. Compacts assumed their final viscoelastic state prior to the time of punch separation. Theory permits separation of material behavior into dilation and distortion components. Dilation, thought to be dependent on voids, was elastic in all cases. Distortion effects could be described well by a Kelvin solid model. Results indicate that viscoelastic properties are functions of compression conditions and may be useful in adjusting compression conditions to avoid problems such as capping.

Dissolution Behavior of Commercial Enteric-coated Aspirin Tablets

Dissolution behavior was studied for four commercial batches of enteric-coated aspirin tablets from two companies. The USP XIX dissolution procedure was modified by including pretreatment in simulated gastric juice. The effects of five pretreatment times were studied. Pretreated tablets yielded higher dissolution profiles and fewer undissolved fractions than nonpretreated tablets. Among pretreatments, 15min was adequate and 60min produced the highest dissolution profiles. None of the pretreatments differed significantly from each other. An F test conducted on the data indicated that Product × was significantly better than Product Y at the p = 0.05 level. Batch C was ranked as the best batch irrespective of pretreatment time, followed by Batch D. Batches A and B were equal, although Batch A appeared to be better than B for the (60-min pretreatment, as indicated by the lower t80% value.

Effect of Microcrystalline Cellulose on Liquid Penetration in and Disintegration of Directly Compressed Tablets

The penetration of isooctane and water into tablets of microcrystalline cellulose, dibasic calcium phosphate dihydrate, spray-crystallized maltose–dextrose, and blends of microcrystalline cellulose with one of the other excipients were studied. The isooctane penetrations occurred according to the Washburn equation and were not affected by the presence of 0.5 or 1.0% magnesium stearate. The inhibition of aqueous penetration into tablets resulting from hydrophobic magnesium stearate was less pronounced for vehicles like dibasic calcium phosphate, which exhibited extensive brittle fracture under compression. Microcrystalline cellulose tablets, both with and without magnesium stearate, exhibited extremely fast aqueous penetration even at low porosities, caused by breaking of the hydrogen bonds and subsequent widening of the pores. Ratios between water uptake and original pore volume up to 20 were obtained for microcrystalline cellulose tablets. This unique property was, however, suppressed by the presence of fast dissolving and highly soluble excipients like dextrose, resulting in an antagonistic disintegration behavior of tablets compressed at pressures over 10,000N/cm2. Improved disintegration properties were obtained by blending microcrystalline cellulose with an insoluble vehicle such as dibasic calcium phosphate dihydrate.

Dissolution Behavior of Commercial Tablets Extemporaneously Converted to Capsules

While conducting double‐blind clinical trials, it is a common practice to convert a commercial tablet dosage form to a capsule so that it may serve as a control drug for the new drug under test. This report will show that when this was done, the in vitro dissolution times of drugs from the capsule dosage forms were strikingly prolonged. Various capsule adjuvants were examined, attempting to decrease dissolution times of drugs from capsules. Of the series tested, lyophilized glycine had the best positive effect in shortening the dissolution times of all drugs examined.

Dissolution Rate Studies I: Design and Evaluation of a Continuous Flow Apparatus

An apparatus for the study of dissolution rate under conditions of continuous flow is described. Typical data are presented; the effect of sample size, surfactant, and flow rate on the dissolution behavior of prednisone powder and prednisone tablets is shown. The requirements of an ideal standard method for studying dissolution rates are discussed, and the major advantages of this method over present methods are pointed out. The method: (a) is more flexible, (b) produces data in a differential form, (c) utilizes a small-volume system which assures greater homogeneity, (d) prevents excessive accumulation of solute in the system, and (e) provides agitation and solvent flow in a controlled, measurable, and physically meaningful manner.

X-ray and Crystallographic Applications in Pharmaceutical Research III. Crystal Habit Quantitation

It is customary practice when describing the crystal habit of a given compound to make use of qualitative terms, such as needles or plates. These terms are useful in describing crystal habit as it relates to some important pharmaceutical characteristics, such as suspension stability and syringeability, but inadequate for the more involved processes in which crystal habit affects tableting ability. In this paper a method is presented for describing the crystal habit of a given compound in quantitative terms which may be used, in some instances, to predict tableting behavior and to serve as specifications for tableting materials.