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At least 649 records · Page 36Linked to original sources

PubMed2004

Time-release compression-coated core tablet containing nifedipine for chronopharmacotherapy.

Compression-coated time-release tablets (CC tablets) containing nifedipine, dihydropyridine Ca channel blocker, in the core tablet were prepared by dry coating with different polyethylene oxide-polyethylene glycol mixtures. Each formulation showed a clear lag period before nifedipine release initiation, followed by sustained drug release lasting up to 24 h. The lag time of nifedipine release increased as the amount of polyethylene oxide in the outer layer increased. To investigate the applicability of such CC-tablets for chronopharmacotherapy, the pharmacokinetics of CC-1 and CC-2 tablets, with different in vitro lag times before drug release, were compared with the pharmacokinetics of a sustained-release (SR) tablet in dogs. The times of first nifedipine appearance (TFA) in plasma were 0.7 +/- 0.3 h for SR, 2.5 +/- 1.2 h for CC-1, and 5.3 +/- 1.0 h for CC-2. These data show a significant difference in in vivo lag time (P < 0.01) among the three formulations that correlates with the in vitro lag times. Thus, the in vivo lag time could be predicted from the in vitro lag time. Additionally, higher plasma nifedipine concentrations were observed at 8 h after administration of the CC-2 than that observed for the SR-tablet. These results indicate that a CC-tablet with a lag time before drug release is a potentially useful formulation for chronopharmacotherapy that can control the time and duration of plasma drug concentration better than existing SR technologies.

Animals↗

PubMed2004

Search for technological reasons to develop a capsule or a tablet formulation with respect to wettability and dissolution.

Proquazone, a poorly wettable compound, was used as a model drug in the search for reasons to develop a capsule or tablet formulation. The capsules were filled with proquazone as active ingredient, with lactose monohydrate (200 mesh) as filler and with magnesium stearate as lubricant. The tablet was made out of a granulate as internal phase which consisted of proquazone as active ingredient, lactose as filler, corn starch as disintegrant and PVP as a binding agent. The external phase consisted of magnesium stearate and corn starch. The concentration of proquazone in the capsule and in the tablet formulation was varied. The capsule formulations showed a significantly slower dissolution of the drug substance than the tablet formulations especially for a high-drug load. Independently of the drug load, only the tablet formulation showed a high-dissolution rate. Thus, concerning drug load, only the tablet formulations showed to be robust. It became clear that proquazone needs to be formulated as a granulate or a tablet to achieve a fast dissolution rate. Thus, a poorly wettable drug, especially when it is found in high concentrations, can have direct impact on the decision to develop a tablet or a capsule formulation.

Capsules↗

PubMed2005

Factors affecting the characteristics of rapidly disintegrating tablets in the mouth prepared by the crystalline transition of amorphous sucrose.

The aim of this study is to investigate the factors affecting the characteristics of rapidly disintegrating tablets containing an amorphous ingredient prepared by crystalline transition method (CTM) under various storage conditions. Effect of storage conditions and formulating ratio of amorphous sucrose on the characteristic changes (tensile strength, porosity, and disintegration time) of the rapidly disintegrating tablets was studied. The storage conditions of different temperature and humidity affected the rate of crystalline transition and the increase in the tablet tensile strength. The faster crystalline transition resulted in a faster rate of increase in the tablet tensile strength. Regarding the effect of the formulating ratio of amorphous sucrose, in the case of 20-100%, the tensile strength after storage as a function of the porosity could be plotted on the same curve. For tablets containing 100% amorphous sucrose, the tablets with different porosity changed to almost the same structure due to the crystalline transition. Hence, the higher formulating ratio of amorphous sucrose provided the longer disintegration time in the mouth. Therefore, we concluded that the formulating ratio of 10-20% of the amorphous sucrose in the tablet is suitable for the rapidly disintegrating tablet in the mouth when prepared by CTM.

Crystallization↗

PubMed2006

Development and evaluation of a novel dry-coated tablet technology for pellets as a substitute for the conventional encapsulation technology.

Pellet formulations as represented by multiparticulate systems are often contained in hard capsules. We examined the use of a different approach to the making of compressed tablets containing pellets, OSDRC-technology. OSDRC-technology employs a double-structure punch (center punch and outer punch) allowing for dry-coated tablets to be assembled in a single run. We examined the effects of the thickness of the outer punch, formability of pellets, and diameter of tablets on pellet filling. The results revealed that thinner outer punches are not always better for filling small tablets with large amounts of pellets. We considered that this was because the core pellets spread in a cone shape within the formulating tablets at filling, requiring a thickness of the outer punch and a particle density of the diluents at which pellets would not exude from the formulating tablets. It was suggested that the formability of core pellets affects the maximum number of layers of pellets, and higher formability would yield better results. However, we found that pellets with poor formability (tensile strength of < or =2 kPa) could be used in tablets. For the tablets, the larger the diameter, the greater the maximum number of layers. We considered this to be due to the friction between the pellets and punch wall. We concluded that OSDRC-technology could be applied to capsule-like forms containing pellets > or =50 wt% through an unconventional approach.

Cellulose↗

PubMed2004

Modulation of combined-release behaviors from a novel "tablets-in-capsule system".

A multifunctional and multiple unit system, which contains versatile mini-tablets in a hard gelation capsule, is developed by preparing Rapid-release Mini-Tablets (RMTs), Sustained-release Mini-Tablets (SMTs), Pulsatile Mini-Tablets (PMTs), and Delayed-onset Sustained-release Mini-Tablets (DSMTs), each with various lag times of release. Based on the combinations of mini-tablets, multiplied pulsatile drug delivery system (DDS), site-specific DDS, slow/quick DDS, quick/slow DDS, and zero-order DDS could be obtained. Velocity-time curve, instead of the cumulative percentage drug release profile, is plotted. The nonlinear least square model fit program is applied to process the velocity data of dissolution. The test curves coincided with the theoretical curves from simple summation of v-t equations of individual mini-tablets. Therefore, the programmed DDS can be predicted by adding the v-t equations of various mini-tablets to calculate the theoretical equations and be implemented.

Administration, Oral↗

PubMed2005

Fast-melting tablets based on highly plastic granules.

Highly plastic granules that can be compressed into tablets at low pressure were developed to make fast-melting tablets (FMTs) by compression method. The highly plastic granules are composed of three components: a plastic material, a material enhancing water penetration, and a wet binder. One of the unique properties of the highly plastic granules is that they maintain a porous structure even after compression into tablets. The porous and plastic nature of the granules allows fast absorption of water into the compressed tablet for fast melting/dissolution of the tablet. The prepared tablets possess tablet strength and friability that are suitable for multi-tablet packages. The three-component highly plastic granules provide an effective way of making FMTs by compression.

Chemistry, Pharmaceutical↗

PubMed2000

Studies on applicability of press-coated tablets using hydroxypropylcellulose (HPC) in the outer shell for timed-release preparations.

Press-coated tablets, containing diltiazem hydrochloride (DIL) in the core tablet and coated with hydroxypropylcellulose (HPC) as the outer shell, were examined for applicability as timed-release tablets with a predetermined lag time and subsequent rapid drug release phase. Various types of press-coated tablets were prepared using a rotary tabletting machine and their DIL dissolution behavior was evaluated by the JP paddle method. The results indicated that tablets with the timed-release function could be prepared, and that the lag times were prolonged as the viscosity of HPC and the amount of the outer shell were increased. The lag times could be controlled widely by the above method, however, the compression load had little effect. Two different kinds of timed-release press-coated tablets that showed lag times of 3 and 6 h in the in vitro test (denoted PCT(L3) and PCT(L6), respectively) were administered to beagle dogs. DIL was first detected in the plasma more than 3 h after administration, and both tablets showed timed-release. The lag times showed a good agreement between the in vivo and in vitro tests in PCT(L3). However, the in vivo lag times were about 4 h in PCT(L6) and were much shorter than the in vitro lag time. The dissolution test was performed at different paddle rotation speeds, and good agreement was obtained between the in vivo and in vitro lag times at 150 rpm. This suggested that the effects of gastrointestinal peristalsis and contraction should also be taken into consideration for the further development of drug delivery systems.

Animals↗

PubMed2000

Plasticisation of amylodextrin by moisture: consequences for drug release from tablets.

Moisture influences the consolidation behaviour of amylodextrin powders and the porosity and mechanical strength of compacts thereof. The aim of this study is to relate moisture content and compact properties to drug release characteristics of amylodextrin tablets. Therefore, amylodextrin tablets containing theophylline monohydrate were prepared and their release characteristics were studied as a function of moisture content and initial porosity. Drug release from amylodextrin tablets occurs through a leaching mechanism in which cracks are progressively formed in the hydrated part of the matrix leading to almost constant release rates. Small variations in moisture content resulted in large changes of the release rate. A unique relationship between porosity and release rate, which was independent on moisture content and compaction pressure, was observed. Above a critical porosity of 0.075 crack formation was followed by disintegration and fast release. Below this critical porosity, tablets stayed intact despite of the formation of cracks, and sustained release was observed. It is concluded that control over moisture content is essential for the production of amylodextrin tablets with reproducible release characteristics. Using amylodextrin containing 10-17%, moisture, tablets with a constant release behaviour can be obtained if sufficient compaction pressure ( > 300 MPa) is applied. Lubrication of amylodextrin powders reduces the effect of porosity significantly and improves the robustness of amylodextrin tablets as a release controlling excipient in tablets largely.

Bronchodilator Agents↗

PubMed2000

Optimisation of floating matrix tablets and evaluation of their gastric residence time.

The present investigation concerns the development of the floating matrix tablets, which after oral administration are designed to prolong the gastric residence time, increase the drug bioavailability and diminish the side effects of irritating drugs. The importance of the composition optimisation, the technological process development for the preparation of the floating tablets with a high dose of freely soluble drug and characterisation of those tablets (crushing force, floating properties in vitro and in vivo, drug release) was examined. Tablets containing hydroxypropyl methylcellulose (HPMC), drug and different additives were compressed. The investigation shows that tablet composition and mechanical strength have the greatest influence on the floating properties and drug release. With the incorporation of a gas-generating agent together with microcrystalline cellulose, besides optimum floating (floating lag time, 30 s; duration of floating, >8 h), the drug content was also increased. The drug release from those tablets was sufficiently sustained (more than 8 h) and non-Fickian transport of the drug from tablets was confirmed. Radiological evidence suggests that, that the formulated tablets did not adhere to the stomach mucus and that the mean gastric residence time was prolonged (>4 h).

Administration, Oral↗

PubMed2003

Analysis of ecstasy tablets: comparison of reflectance and transmittance near infrared spectroscopy.

Calibration models for the quantitation of commonly used ecstasy substances have been developed using near infrared spectroscopy (NIR) in diffuse reflectance and in transmission mode by applying seized ecstasy tablets for model building and validation. The samples contained amphetamine, N-methyl-3,4-methylenedioxy-amphetamine (MDMA) and N-ethyl-3,4-methylenedioxy-amphetamine (MDE) in different concentrations. All tablets were analyzed using high performance liquid chromatography (HPLC) with diode array detection as reference method. We evaluated the performance of each NIR measurement method with regard to its ability to predict the content of each tablet with a low root mean square error of prediction (RMSEP). Best calibration models could be generated by using NIR measurement in transmittance mode with wavelength selection and 1/x-transformation of the raw data. The models build in reflectance mode showed higher RMSEPs using as data pretreatment, wavelength selection, 1/x-transformation and a second order Savitzky-Golay derivative with five point smoothing was applied to obtain the best models. To estimate the influence of inhomogeneities in the illegal tablets, a calibration of the destroyed, i.e. triturated samples was build and compared to the corresponding data of the whole tablets. The calibrations using these homogenized tablets showed lower RMSEPs. We can conclude that NIR analysis of ecstasy tablets in transmission mode is more suitable than measurement in diffuse reflectance to obtain quantification models for their active ingredients with regard to low errors of prediction. Inhomogeneities in the samples are equalized when measuring the tablets as powdered samples.

Amphetamines↗

PubMed2000

Effect of compression force on the crystal properties of erythromycin acistrate tablets.

The crystal properties of compressed and powdered erythromycin acistrate tablets were studied by the X-ray powder diffraction (XRPD) method. Detailed analysis of X-ray powder diffraction line profiles was performed. Diffraction peak intensities and full width at half maximum (FWHM) values of the peaks corresponding to three different crystal lattice directions were determined. Crystallite size was calculated by Scherrer's equation using the data of integral breadth of the peaks. The preferred orientation of the crystallites is also discussed. According to the results, the crystallite size increased on the tablet surface after a small compression force (4 kN) in all crystal lattice directions studied. Even small compression forces caused recrystallization. With higher compression forces (8-18 kN) the crystallite size and the FWHM values remained rather constant. After the compression force of 18 kN the peaks in different crystal lattice directions behaved differently. In the lattice directions of diffraction maxima 2 and 3, the effect was the same with the small (4 kN) and the high compression force (22 kN). Further recrystallization occurred with 22 kN. However, in the crystal lattice direction of diffraction maximum 1 at the compression force of 8 kN the crystallite broke and crystallinity decreased. These were not seen in the powdered tablet samples. It could be concluded that the effect of compression force on the crystal properties of erythromycin acistrate tablets was seen on the tablet surface but not in the powdered tablets. Compression force also affected the preferred orientation of crystallites on the tablet surface and especially in the lattice direction of diffraction maximum 3. This was not seen in the powdered tablets.

Chemistry, Pharmaceutical↗

PubMed2001

Enzymatic degradation of cross-linked high amylose starch tablets and its effect on in vitro release of sodium diclofenac.

The influence of several physicochemical parameters on enzymatic hydrolysis and the in vitro release of sodium diclofenac (SDic) from cross-linked high amylose starch (Contramid) (CLA) tablets was evaluated. These parameters included pH, ionic strength of the medium, enzyme concentration, compression force and incorporation of gel-forming polymers such as hydroxypropyl methylcellulose (HPMC), poly(ethylene oxide) (PEO) and poly(vinyl alcohol) into the tablet. Pure CLA tablets were incubated in phosphate buffer (pH 6.8) containing alpha-amylase and the extent of enzymatic erosion was determined by gravimetry. Release of SDic from CLA tablets, in the presence of alpha-amylase, was measured using a USP type III dissolution apparatus. For low alpha-amylase concentrations (<2250 IU/l), the drug release was mainly diffusion-controlled. At higher alpha-amylase concentrations (>4500 IU/l) both diffusion and erosion contributed to the release of SDic. The hydrolysis kinetics of CLA tablets by alpha-amylase was biphasic. During the first phase (2-4 h), the hydrolysis rate was hyperbolically related to the alpha-amylase concentration but was practically alpha-amylase concentration-independent during the second phase. Enzymatic erosion and drug release kinetics appear to be relatively independent of ionic strength, pre-incubation time in simulated gastric fluid, and compression force of the tablets (6-34 kN). Incorporation of HPMC or PEO into the tablet resulted in a significant decrease of both tablet erosion and drug release rates.

Amylose↗

PubMed2001

Controlled-release tablets from carrageenans: effect of formulation, storage and dissolution factors.

The purpose of this study was to investigate the potential of two carrageenans, iota-carrageenan and lambda-carrageenan for the preparation of controlled-release tablets. Tablets were compressed on a Carver press and the effect of formulation factors, moisture, and storage on the release of theophylline was studied. The effect of sodium chloride in the tablet formulation and a change in the ionic strength of the dissolution media was studied on the release of three model drugs. The release rate increased both with an increase in tablet diameter and increase in drug to carrageenan ratio in the tablets. The two lubricants studied had a negligible effect on the rate of drug release at their commonly used concentrations. Moisture content of carrageenans, storage of tablets at 37 degrees C/75% RH for 3 months, and incorporation of 10% sodium chloride in the tablets did not have any significant effect on the release rate. The change in ionic strength of simulated gastric fluid altered the release rate whereas the ionic strength of simulated intestinal fluid did not have a significant effect on the release rate. Carrageenan tablets were relatively insensitive to small changes in formulation parameters and dissolution conditions.

Carrageenan↗

PubMed2003

Coating uniformity and coating efficiency in a Bohle Lab-Coater using oval tablets.

The aim of this study was the examination of the influence of tablet size (two different sized oval tablets), batch size, pan speed and inclination of the rotation axis on the coating uniformity and efficiency in a Bohle Lab-Coater BLC 5. The coating uniformity was appraised using the mass variance, the dissolved amount of acetaminophen after 2 h in hydrochloric acid pH 1.0 at a polymer loading of 3 mg/cm(2) and the minimum amount of polymer for an enteric coating. The mass variance of the final tablets decreased with increasing pan speed. There was a linear and quadratic effect in the case of small oval tablets and a linear effect for the large tablets. The minimum amount of polymer required for gastric resistance depends on the pan speed for both tablet sizes. The dissolved amount of acetaminophen after 2 h in simulated gastric fluid was influenced linearly by the batch size for both kind of tablets. In the case of the large oval tablets it was also influenced by the pan speed, the batch size and the inclination of the rotation axis. The dissolved amount of acetaminophen increased with increasing pan speed and batch size. A relation between the coating process efficiency and the investigated influence variables could not be established.

Acetaminophen↗

PubMed2003

Stabilization of sodium guaiazulene sulfonate in granules for tableting prepared using a twin-screw extruder.

Sodium guaiazulene sulfonate (GAS-Na), which has an anti-inflammatory effect, is an unstable compound, which is gradually decomposed in the solid state at room temperature. In fact, when heated (40 degrees C 6% RH), GAS-Na decomposes almost completely within 1 week. It was found that a kneaded mixture of GAS-Na and cornstarch (weight ratio; 1:250) for tableting with water is stable. So, during production, GAS-Na could be stabilized using water. Four kinds of tablet were prepared in different ways: direct tableting, tableting via screw granulation, tableting via fluidized bed granulation, and tableting via twin-screw extrusion. The stability of GAS-Na in these tablets was compared. The tablet prepared using screw granulation, during which 30% water was added to the material, was the most stable. It was, however, shown that reducing the water content to 12.5%, when screw granulation was conducted, made the GAS-Na less stable. Also, when a twin-screw extruder with kneading paddle elements in the screws was used even with lower water content of 12.5%, the stability of GAS-Na improved. In addition, when the kneading paddle elements were detached from the screws and only the feed screw elements were operated, GAS-Na lost its stability. These results show that the kneading paddle elements play a role in uniformly dispersing a small amount of water into the powder and stabilizing GAS-Na. It was found that the water presence was a very important factor with respect to the decomposition of GAS-Na, irrespective of the crystallinity. Furthermore, a twin-screw extruder with kneading paddle elements is useful for uniformly dispersing water to prepare stable formulations of GAS-Na.

Azulenes↗

PubMed1998

In vitro and in vivo erosion of two different hydrophilic gel matrix tablets.

The aim of the present work was to establish in vivo predictive in vitro tests for the tablet erosion of two different compositions (A and B) of hydrophilic matrix tablets based on hydroxypropyl methylcellulose. The tablet erosion was studied in a modified USP II apparatus at different agitation intensities and ionic strengths according to 2(2) factorial design. The in vivo tablet erosion was studied in 8 healthy human volunteers by gamma scintigraphy after administration of the tablets together with breakfast. In vitro agitation intensity increased the erosion rate for both tablets whereas increased ionic strength caused a slower rate for tablet A and a faster rate for tablet B. The choice of in vitro testing conditions proved to be critical for the attainment of in vivo predictive results. The best in vitro/in vivo correlation for the two formulations was obtained at a paddle stirring rate of 140 rpm and a ionic strength of 0.14 obtained by addition of sodium chloride.

Adult↗

PubMed2001

Influence of crystal structure on the tableting properties of sulfamerazine polymorphs.

PURPOSE: To understand the influence of polymorphic structure on the tableting properties of sulfamerazine. METHODS: Bulk powders of sulfamerazine polymorph I and of two batches. II(A) and II(B) of different particle size, of polymorph II were crystallized. The powders were compressed to form tablets whose porosity and tensile strength were measured. The relationships between tensile strength, porosity and compaction pressure were analyzed by the method developed by Joiris. E., et al. Pharm. Res. 15:1122-1130 (1998). RESULTS: The sensitivity of tensile strength to compaction pressure, known as the tabletability, follows the order. I >> II(A) > II(B) and the porosity at the same compaction pressure, which measures the compressibility, follows the order, I << II(A) < II(B). Therefore. the superior tabletability of I over II(A) or II(B) is attributed to its greater compressibility. Molecular simulation reveals slip planes in crystals of I but not in II. Slip planes provide I crystals greater plasticity and therefore greater compressibility and tabletability. Larger crystal size of II(B) than of II(A) leads to fewer contact points between crystals in the tablets and results in a slightly lower tabletability. CONCLUSIONS: Slip planes confer greater plasticity to crystals of I than II and therefore greater tabletability.

Anti-Infective Agents↗

PubMed1992

Application of curdlan to controlled drug delivery. I. The preparation and evaluation of theophylline-containing curdlan tablets.

To study the use of curdlan, a natural beta-1,3-glucan, in drug delivery, in vitro release studies were carried out with curdlan tablets containing theophylline. Tablets were readily prepared by compressing three different curdlan and theophylline mixtures, namely, a physical mixture, spray-dried curdlan particles with theophylline powder, and spray-dried particles of curdlan/theophylline solution. Drug release from the tablets prepared from spray-dried particles of curdlan/theophylline was lowest. The release rate was constant from 1 to 8 hr, and 59% cumulative release was obtained at 8 hr. Drug release from curdlan tablets was unaffected by pH or various ions; these curdlan tablets might also control drug release in vivo after oral administration. Application of Higuchi's equation indicated that drug release from curdlan tablets was diffusion-controlled. The release profiles of the curdlan tablets were compared to those of a commercial theophylline sustained-release tablet.

Chemistry, Pharmaceutical↗