Tablets preparation method

The availabihty of spray-dried lactose, microcrystaUine cellulose, and other excipients allows for the use of granular rather than powdered phases. This eliminates some of the problems of particle segregation according to size (demixing) and even flow to the die. Direct compression eventually may be the preferred method of tablet preparation. 

This technique has also been used in combination with nitrogen absorption to study the pore structure of some excipients, particularly MCC in both the powdered and compacted state. The intraparticulate porosity of MCC has been shown to be unaffected by tableting the interparticular pores, however, are gradually reduced in size [38]. Recently this method has been used to evaluate the internal structure of tablets prepared from microcapsules [150]. 

The tableting indices methods, summarized in Table 1, require powder compacts that are prepared under carefully controlled conditions so that they are essentially free of flaws (4,7). These compacts are the samples used for indentation hardness and TS measurements. 

According to the Pharmacopoeia of the People s Republic of China [7], the method of identification testing of mefenamic acid in capsule and tablet preparations is based on light absorption spectrophotometry. A specific quantity of the powdered contents of capsules (or powdered tablets), equivalent to 0.25 g mefenamic acid, is dissolved in a mixture of 10 mL of 0.1 mL/L hydrochloric acid/methanol (1 99), shaken, and filtered. Then some quantity of the filtrate is diluted with the above-mixed solution to produce a solution having a concentration of about 20 pg/mL. The absorption spectrum of the solution exhibits maxima at 279 nm and 350 nm. 

The method was applied directly and easily to the analysis of the pharmaceutical tablet preparations. Mean percent relative standard deviation was foimd to be 0.6231% (Longifene tablet 25 mg). The method was completely validated and proven to be rugged. This validated UV spec-trophotometric method is potentially useful for a routine laboratory analysis because of its simplicity, rapidity, sensitivity, precision, and accuracy. 

Preparation methods Tableting Extrusion Fluid/spouted bed... 

The technique of Malkowska and Khan, " used as described before to determine the capacity of a direct compression diluent, was originally developed as a method of expressing the ability of a formulation to be reworked. Referring to Fig. 2, the upper curve represents the strength of tablets prepared without reworking and the lower curve is the strength of reworked tablets. The reworking index is calculated from the ratio of the areas under the curves as described previously. 

Bi YX, Sunada Y, Yonezawa Y, Danjo K. Evaluation of rapidly disintegrating tablets prepared by a direct compression method. Drug Dev Ind Pharm 1999 25(5) 571-581. 

At this point, there usually follows a chapter about the pretreatment of the samples. However, in contrast to HPLC/GC, sample preparation for TLC is not considered to be quite as critical. As well as the use of precoated layers with a concentration zone (e.g. an application zone consisting of silica 50 000 and a separation zone of sihca gel 60 or RP-18 material) upon which the matrix constituents can often be held back by suitable choice of solvent system, a chromatogram that is imusable for lack of sample preparation is more rapidly rectified (use a different preparation method and a new plate ) than an irreversibly destroyed column. A detailed treatment of the subject of sample preparation would exceed the scope of the present book. In Section 9.4, rm-der the title Examples of GMP/GLP-Conforming Testing Procedures , we describe the extraction of a pharmaceutically active substance from a tablet and the working up of plant components from dry extracts. The reader is referred to other TLC textbooks [2,21] and to literature and brochures produced by manufacturers of articles for sample preparation [28, 29]. 

In Chapter 18, we described solvent extraction and solid-phase extraction sample preparation methods, which are applicable to GC analyses as well as others. A convenient way of sampling volatile samples for GC analysis is the technique of head-space analysis. A sample in a sealed vial is equilibrated at a fixed temperature, for example, for 10 min, and the vapor in equilibrium above the sample is sampled and injected into the gas chromatograph. A typical 20-mL glass vial is capped with a silicone rubber septum lined with polytetrafluoroethylene (PTFE). A syringe needle can be inserted to withdraw a 1-mL portion. Or the pressurized vapor is allowed to expand into a 1-mL sample loop at atmospheric pressure, and then an auxiliary carrier gas carries the loop contents to the GC loop injector. Volatile compounds in solid or liquid samples can be determined at parts per million or less. Pharmaceutical tablets can be dissolved in a water-sodium sulfate solution... 

In the second method, the amount of Form C transformed from Form A at 45°C was about two times larger than that at 0°C at the same compression energy. The crushing strength of tablets prepared from Form A was about twice that of tablets manufactured using Form C as the source of drug substance. 

Figure 2 shows PMMA infrared spectrum from different sample preparation methods. The PMMA infrared spectrum from powder pulverized tablet and hot-pressing film are nearly same on wavemmbers, and slightly different on wave intensity. But there is another additional infrared eigen wave (at 760 cm-i) for PMMA infrared spectrum from solution film casting method (chloroform resolving). 

Most pharmacopoeias specify that ethambutol hydrochloride contains not less than 98.0% and not more than 100.5% of C10H24N2O2 2HCI, calculated on the dried basis. Pharmaceutical products such as tablets must contain not less than 95.0% and not more than 105.0% of the labeled amount.As for pyrazinamide, the main pharmacopoeia assay method for ethambutol is a titration method. However, an HPLC method is used for the assay of ethambutol HCl in tablets.This method requires that a liquid chromatograph equipped with a 200-nm detector and a 4.6 mm X 15 cm base-deactivated column that contains 5 p,m porous silica particles, 3-10 p,m in diameter, with chemically bonded nitrile groups (CN, LIO) is used. The mobile phase is a mixture of 1.0 ml of triethylamine and 1 L of water, adjusted with phosphoric acid to a pH of 7.0. The flow rate is about 1.0 ml/min. Separately inject equal volumes (about 50 p.1) of standard preparations and the assay preparations into the chromatograph, record the chromatograms, and measure the responses for the major peaks and calculate the quantity, in mg, of ethambutol hydrochloride present in the tablets from the peak responses obtained from the assay preparation and the standard preparation, respectively. The tailing factor must not be more than 2.0, and the relative standard deviation for replicate injections not more than 2.0%. 

Tablets are prepared by compression of uniform volumes of particles (powder mixtures) or granules. The choice of excipients depends on the preparation method wet granulation or direct compression.

Formulation and preparation method of modified-release tablets is tuned to the desired release profile, and thus differ from conventional tablets. The complex nature of this for-muladcHi and preparation can only occur in large-scale industrial production. 

The great advantage of this method for effervescent tablet preparation lies in the installation of equipment that does not require explosion-proof systems. An example of effervescent aspirin produced in 600 L high-shear granulator-dryer equipped with vacuum and tilting bowl (29) is shown in Figure 5. 

This hypobromite method has largely been replaced by the more accurate and specific urease process. Urease will rapidly hydrolyse urea into ammonium carbonate and fairly stable preparations of the enzyme are available in the form of tablets. The method for the estimation of urea in urine due to Dunning is applicable using these tablets ... 

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