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Acta Pharm. 60 (2010) 267280 10.2478/v10007-010-0025-8 Original research paper MADHUSUDHAN MALLADI1 RAJU JUKANTI2* RASHMI NAIR1 SANJAY WAGH1 HARI SHANKER PADAKANTI2 ASHOK MATETI2 1 CPS Formulations, DR. Reddy's Laboratories Limited, Bachupally Hyderabad-500090, India 2 Department of Pharmaceutics St. Peter's Institute of Pharmaceutical Sciences, Vidyanagar, Hanamkonda Warangal-506001, India The present study is aimed to develop dextromethorphan hydrobromide (DXM) oral disintegrating tablets (ODT) with acceptable palatability to help patients of all age groups. The bitter taste of the drug was masked by binding the drug to ion exchange resin. The effect of the particle size of resin on drug loading was studied. In vitro and in vivo disintegration time and in vitro drug release studies were performed. Drug loading increased significantly with a decrease in the particle size of the resin. DSC and XRPD studies reveal that the molecular state of the drug changed from crystalline to amorphous form. The dissolution efficiency calculated for optimized ODT and conventional directly compressed tablet were almost comparable, indicating free dissociation of the drug from the resinate. The bitter taste of DXM can be masked by binding with ion exchange resin and the resinate can be successfully formulated into oral disintegrating tablets. Keywords: dextromethorphan hydrobromide, ion exchange resin, taste masking, superdisintegrants Accepted July 30, 2010 Oral disintegrating tablets (ODTs) have advantages of solid dosage forms such as good stability, accurate dosing, small packaging size, and easy handling, as well as those of liquid formulations such as easy administration and minimal risk of suffocation. Therefore, they are beneficial for children, elderly and schizophrenic patients who have difficulty in swallowing conventional solid dosage forms (1). The success of ODT depends on patient acceptance, palatability and the challenging aspect in the formulation of orally disintegrating tablets is to mask the bitterness of active pharmaceutical ingredients, since most drugs have bitter taste. The distasteful sensation of a drug can be masked either by the addition of flavors, sweeteners and effervescent agents or by reducing direct contact with the patient's taste buds through coating or granulation (2, 3). Flavor is often overpowered by the taste of the medicine and the use of effervescent agents is not always convenient. Moreover, coating and granulation of the active ingredient may * Correspondence; e-mail: email@example.com M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. often rupture during compression and chewing of the tablet, as well as contribute to a gritty feel. Drug binding to ion exchange resin is a simple and efficient technique of masking drug bitterness. Active ingredients, if ionized, can be bound with fixed ions of ion-exchange resins (46). The advantages of utilizing ion-exchange resins include the simple preparation method and no uncontrolled burst effect in the drug resinate even in case of high drug loading. The only limiting factor for drug loading is the limited exchanging capacity of the resin. Particle size of the resin has been reported to have a pronounced effect on the rate and extent of drug loading (7). When active ingredient/resin complexes are administered orally, the active ingredient can be released by the ion-exchange reaction with ions present in the GI tract. Dextromethorphan hydrobromide is an antitussive agent, used to relieve cough. The commercial formulations available for DXM are syrups, lozenges and spray forms but its availability as solid dosage forms is limited. Since liquid dosage forms are bulky and stability is a key issue, we decided to develop taste masked ODTs of DXM for immediate relief of cough with improved patient compliance. This could be achieved by selecting appropriate pharmaceutical excipients in correct proportion, in combination with optimal manufacturing techniques and compression parameters. EXPERIMENTAL Materials Ion-exchange resin (Amberlite® IRP69, sodium polystyrene sulfonate (150125, 10675 and 6345 mm) was donated by Rohm and Haas, USA. Dextromethorphan hydrobromide monohydrate (DXM) was obtained from Dr. Reddy's Laboratories Ltd, India. The diluents used were spray-dried mannitol (Pearlitol® SD 200, Roquette Frères, France) and microcrystalline cellulose (Avicel PH 101, FMC International, Ireland). The superdisintegrants used were Crospovidone (CP) (Polyplasdone XL-10, ISP Technologies, Inc, USA), sodium starch glycolate NF (SSG) (Primojel, DMV International, USA) and Amberlite IRP88 (potassium salt of methacrylic acid polymer with divinyl benzene, Rohm and Haas, USA). The glidants used were colloidal silicone dioxide NF (Aerosil®, Evonik Industries Degussa, Belgium) and sodium starch fumarate (JRS Pharma, Spain). The flavor used was tutti frutti flavor (Firmenich, India). All other chemicals and solvents used were of analytical grade. Methods Preparation of drug resinate. Drug resinates were prepared by a single batch process. Purified resin (3.0 g) was placed in 200 mL of 1.5 % (m/V) of DXM aqueous solution. The mixture was stirred for 24 h on a magnetic stirrer at ambient temperature and intermittently the supernatant was removed to find out the amount of drug loaded in the resin spectrophotometrically at 278 nm (UV-2450/2550, Shimadzu, Japan). The resinate was retrieved by filtration and washed repeatedly with deionized water until the free drug was removed. The resinates were dried for 2 h at 60 °C and stored in a tightly M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. closed vial. The drug content in the final filtrate was analyzed at 278 nm. The amount of drug in the resinate was obtained by subtracting the amount of drug in final filtrate from the initial amount. Since the particle size of resin influences the extent of drug loading, we have tested different ranges of Amberlite® IRP69 particle size. In vitro dissolution. Dissolution study on resinates of different particle size (150125, 10675 and 6345 mm) equivalent to 30 mg of DXM was carried out in 900 mL of simulated gastric fluid (SGF), without enzymes, using USP dissolution apparatus (8), type II (rotating paddle), maintained at 37 ± 0.5 °C and mixed at 50 rpm. Based on the dissolution data, we have selected Amberlite IRP69 of particle size 6345 mm for further studies. Differential scanning calorimetry (DSC). The molecular state of the drug in the resinate was evaluated by performing DSC analyses of pure drug, resin, physical mixture and resinate. DSC curves of the samples were obtained with a differential scanning calorimeter (DSC 6, Perkin Elmer, USA). Each sample was placed in an aluminum pan and then crimped with an aluminum cover. Heating and cooling rates were 10 and 250 °C min1, respectively. All measurements were performed over 40250 °C under a nitrogen purge at 50 mL min1. X-ray powder diffraction. The XRPD patterns of pure drug, resin, physical mixture and resinate were obtained using an X-ray diffractometer (X' Pert PRO PANalytical, USA). The measuring conditions were as follows: CuKa radiation, nickel filtered, graphite monochromator, 45 kV voltage and 40 mA current with X'celerator detector. All samples were run at 1° (2q) min1 from 3 to 45 ° (2q). FTIR spectroscopy. Chemical interaction between the drug and resin was studied by FTIR spectroscopy. The IR spectra of the samples were obtained using a Fourier transform infrared spectrometer (Perkin Elmer, USA). Measurements were carried out according to the KBr disk method, the scanning range was 4000 to 450 cm1. Table I. Composition of DXM oral disintegrating tablets Disintegrant concentration CP/SSG/ IRP88 (%, m/m) Ingredient 3 Drug-resinate (32.5 %) (mg) Pearlitol® SD 200 (mg) Avicel pH 101 (20 %) (mg) Superdisintegrants (mg) Aspartame (0.5 %) (mg) Aerosol® (1 %) (mg) Sodium stearyl fumarate (0.5 %) (mg) Total (mg) 65 85 40 6 1 2 1 200 5 65 81 40 10 1 2 1 200 10 65 71 40 20 1 2 1 200 CP, SSG and IRP88 indicate Crospovidone, sodium starch glycolate and ion exchange resin, respectively. M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. Formulation of DXM oral disintegrating tablets. In our preliminary studies, ODTs were prepared using superdisintegrants like Crospovidone (CP), sodium starch glycolate (SSG) and amberlite IRP88 at various concentrations (3, 5 and 10 % m/m, respectively). The composition of ODTs prepared with different concentrations of superdisintegrants is shown in Table I. Based on the disintegration time, the type and concentration of superdisintegrant was selected and different batches of ODTs (A1, A2 and A3) containing diluents like Avicel PH 101 and Pearlitol SD 200, either alone or in combination, were prepared as outlined in Table II. All formulation components were accurately weighed, passed through a 0.4-mm sieve (except lubricant) and mixed in a polyethylene bag for 15 min. The blend was lubricated with sodium stearyl fumarate and Aerosil® (each passed through 0.25-mm mesh) for another 5 min and directly compressed into tablets using an 8-station rotary tablet compression machine (Kambert, India). Round biconvex tablets of 200 mg in mass and 8 mm in diameter were prepared. Conventional tablets were also prepared with the same formula (A1) using DXM instead of drug-resinate. Evaluation of DXM oral disintegrating tablets Mass variation, thickness and assay. Mass variation was carried out using a digital balance (Shimadzu) and thickness was measured with a digital screw gauge micrometer (Digimatic micrometer Series 293, Mitutoyo, Japan). Accurately weighed amount of powder equivalent to a single dose of DXM was taken, in triplicate, and assayed for the drug content. Hardness, friability and in vitro disintegration time. Hardness, friability and in vitro disintegration time (DT) of ODTs was determined as per the procedure described for uncoated tablets in USP (8). Wetting time and water absorption ratio. The wetting time (WT) and water absorption ratio (R) were determined by using the procedures described in literature (9). Taste evaluation and in vivo disintegration time. The study was conducted after prior approval from the Institutional Ethical Committee, St Peter's Institute of Pharmaceutical Sciences, Warangal, India. After informed consent from six human volunteers, taste evaTable II. Composition of DXM oral disintegrating tablets containing different diluents Ingredient Drug-resinate (32.5 %) (mg) Pearlitol® SD 200 (mg) Avicel pH 101 (mg) Superdisintegrants (10 %) (mg) Aspartame (0.5 %) (mg) Aerosil® (1 %) (mg) Sodium stearyl fumarate (0.5 %) (mg) Total (mg) A1 65 111 20 1 2 1 200 A2 65 111 20 1 2 1 200 A3 65 77 34 20 1 2 1 200 M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. luation was done by the time intensity method (10). Resinates equivalent to 30 mg of DXM and ODT formulations, with and without flavor, were held in the mouth of six volunteers for 30 seconds. Bitterness was recorded immediately according to the bitterness intensity scale from 0 to 3 where 0, 0.5, 1, 2, and 3 indicate no, threshold, slight, moderate and strong bitterness, respectively. The readings were taken immediately and at several intervals over a period of 10 min. Oral DT of the optimized ODT formulation (determined based on its in vitro DT and drug release) was assessed on six healthy male human volunteers according to the procedure described by Abdelbary et al. (11). The subjects were informed of the purpose and protocol of the study. As per the protocol, all volunteers were asked to rinse their mouth with distilled water prior to the test. Tablets were placed on the tongue and a stopwatch was started immediately. Volunteers were allowed to move the tablet against the upper palate of the mouth with their tongue and cause a gentle tumbling action on the tablet without chewing it. Time taken for the volunteer to feel that the last noticeable granule had disintegrated in the oral cavity was considered the in vivo DT. Swallowing of saliva was prohibited during the test, and the mouth was rinsed after each measurement. This experiment was conducted on all six subjects and the mean ± SD were calculated for each. In vitro release. Release studies of ODTs were performed according to the USP (8) type-II dissolution apparatus (Model-TDL 08L, Electrolab, India), equipped with an auto sampler and fraction collector. Paddle speed was maintained at 50 rpm and 900 mL of simulated gastric fluid without enzymes was used as the dissolution medium. Samples (5 mL) were collected at predetermined time intervals and replaced with an equal volume of fresh medium to maintain sink conditions. The samples were filtered through a 0.45-mm membrane filter (Millipore, USA) and analyzed spectrophotometrically at 278 nm. Conventional tablets of DXM containing the same formula as A1 batch (DXM instead of drug-resinate) were prepared by direct compression to compare the dissolution behavior of ODT. Cumulative percent drug release was plotted as a function of time. Dissolution efficiency (DE) was calculated from the area under the dissolution curve at time t (measured using the trapezoidal rule) and expressed as a percentage of the area of the rectangle described by 100 % dissolution over the same time (12). RESULTS AND DISCUSSION Initially, ODTs containing superdisintegrants in concentrations of 3, 5, and 10 % (m/m) were tested for disintegration time. The tablets showed disintegration time of 810 s, 1317 s and 1320 s with Crospovidone, sodium starch glycolate and Amberlite IRP88, respectively (Table III). Among the superdisintegrants tested, CP at a concentration of 10 % m/m showed lower disintegration time. Since lower disintegration time is required for an ODT, we have selected CP at a concentration of 10 % m/m, for formulations of ODTs. M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. Drug loading (%) 40 150125 mm 10675 mm 20 6345 mm 0 0 5 10 15 Time (h) 20 25 30 Fig. 1. Effect of particle size of ion-exchange resin on drug loading (mean ± SD, n = 3). Drug loading and in vitro dissolution from different particle size resinates Drug loading was 85 % with the resin particle size 6345 mm and this was reduced to 75 and 50 % with an increase in the particle size of resin to 10675 and 150125 mm, respectively (Fig. 1). A linear relation of drug loading to resin particle size was established. As the particle size decreased, the drug loading increased significantly (7). Similar observations were made in our study as well. Fine particles have a larger surface area than coarse particles and less internal volume for ions to diffuse, so less time is required to establish equilibrium. Similarly, desorption of bound drug from the complex is faster in fine particles. Particle size of resinate had an impact on the dissolution rate, as the sustained release was more evident from larger particles (13). From the dissolution profiles along with cross-linking, particle size was reported to be an important factor in controlling the Table III. Effect of superdisintegrants on in vitro DT of DXM oral disintegrating tablets Superdisintegrant (%, m/m) 3 Crospovidone 5 10 Sodium starch glycolate 3 5 10 3 Amberlite IRP 88 5 10 DT dissolution time In vitro DT (s) 9.27 10.41 8.50 13.54 15.42 17.51 13.20 20.03 19.63 M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. Cumulative drug release (%) 60 150125 mm 10675 mm 40 6345 mm Fig. 2. Dissolution profiles of different particle size resinates in simulated gastric fluid (pH 1.2) (mean ± SD, n = 3). 0 0 1 2 3 4 Time (h) 5 6 7 8 release of the drug from ion exchange resin (14). The reduced dissolution behavior of DXM from resinate with larger particle size might be due to the hurdles in drug movement through the polymeric network requiring more time for deeply penetrated drug molecules to elute. The dissolution of DXM was much higher from resinate with particle sizes 6345 and 10675 mm compared to 150125 mm particle size resinate (Fig. 2). Since particle size is an important parameter for improved dissolution characteristics, we have selected the resinate with smaller particle size of 6345 mm. Molecular interactions of drug and resin Molecular interactions between drug and resin were studied using differential scanning calorimetry, X-ray powder diffraction and Fourier transform infrared spectroscopy. Fig. 3 represents the DSC curves of DXM, Amberlite® IRP69, physical mixture and resinate. A sharp endothermic peak was observed at 123.07 °C for pure drug, indicating the melting point of DXM. The endothermic peak of pure drug was also shown in case of the physical mixture at 120.1 °C. On the other hand, no intense peak over the range of 40250 °C was found in the DSC thermogram of resinate, which clearly indicates that the drug was not in its native form in the resinate. This finding could be considered indicative of drug amorphization as a consequence of interaction between the components (15), which was further confirmed by XRPD analysis. The XRPD of the pure drug contained a number of sharp peaks, while the resin showed diffused peaks. The XRPD of the physical mixture exhibited simply the sum of characteristic peaks of the pure drug and diffused peaks of the resin, whereas the characteristic peaks of the pure drug were absent in the resinate (Fig. 4). On the basis of diffractograms, it can be said that pure crystalline drug was found to convert into amorphous form with monomolecular dispersion in the resin (16). This was supported by the absence of sharp peaks of the drug in the resinate. These results coincide with those obtained by Akkaramongkolporn and co-workers (17), who studied the change in molecular properties of propranolol upon binding with an ion exchanger. M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. drug resinate physical mixture Heat flow amberlite IRP69 20 dextromethorphan 30 40 60 80 100 120 140 160 180 200 220 240 Temperature (°C) Fig. 3. DSC curves of dextromethorphan, Amberlite IRP69, physical mixture and drug resinate. From Fig. 5, it is evident that the FTIR spectra of the physical mixture exhibited superimposition of the drug and resin spectra. This indicates that there was no appreciable interaction between the drug and resin in the physical mixture, which is in accord with the results from DSC and XRPD. The spectra of the resinate in the 2000400 cm1 region had a similar result, demonstrating the presence of the drug in the complex. However, Counts 4000 2000 0 400 200 0 15000 10000 5000 0 3000 2000 1000 0 10 20 30 Position [°2Theta] (Copper (Cu)) 40 drug resinate amberlite IRP69 dextromethorphan physical mixture Fig. 4. XRPD patterns of dextromethorphan, Amberlite IRP69, physical mixture and drug resinate. M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. 2833.33,36.24 2152.17,50.09 2579.71,38.78 2927.53,28.11 2152.17,63.49 1613.40,38.72 drug resinate Transmittance (%) 2833.33,50.24 2927.53,31.77 2833.33,48.14 1613.40,46.48 2579.71,41.60 dextromethorphan 2152.17,56.61 1613.40,44.59 2927.53,31.77 2927.53,34.91 2833.33,50.21 physical mixture 2152.17,53.37 2579.71,52.39 1613.40,48.47 2927.53,45.67 Fig. 5. FTIR spectra of dextromethorphan, Amberlite IRP69, physical mixture and drug resinate. amberlite IRP69 1000 450 Wavenumber (cm1) around 40002000 cm1 the spectrum was obviously different from the combination of each component. Drug spectrum shows that prominent absorption bands at 2167.03 and 2593.69 cm1, corresponding to the NH+ stretching vibration in the tertiary amine group of the drug, disappeared (or shifted) in the resinate. In addition, new absorption bands emerged around 3022.89 cm1 in the resinate spectra. In comparison with certain absorption bands around this wavelength position, the distinct increase in intensity of the new absorption bands in the resinate spectra indicates that they are not the usual absorption bands associated with either pure drug or resin. The formation of new chemical bonds would be expected to result in emergence of additional absorption bands or alterations in wavenumber position (18). From this standpoint, the above finding can imply that dextromethorphan in resinate exists in the positively charged form (NH+ group of drug in resinate), which interacts with the sulfonate group of the resin in the complex. This kind of ionic association is referred to as a »salt bridge«. Like the hydrogen-bonding effect, the degree of this ionic association, which closely relates to the H-donating and accepting ability of an ion pair, significantly affects the NH+ stretching. As the ionic association increases, the NH+ stretching decreases and subsequently shifts to a lower frequency, and vice versa. Therefore, the shifting of the NH+ stretching of the drug to a higher frequency in resinate suggests that the ionic association in resinate is weaker than in the drug (19). Evaluation of tablets Initially, tablets containing superdisintegrants in concentrations of 3, 5, and 10 % (m/m) were tested for disintegration time. The tablets containing CP showed fast disintegration (810 s) followed by SSG (1317 s) and Amberlite IRP88 (1320 s) (Table III). Based on the results, CP at a concentration of 10 % was selected for the formulations of ODTs. Tablet thickness and hardness were maintained at 4.5 ± 0.1 mm and 3.5 ± 0.5 kg cm2, respectively, for all formulations. The mass variation (less than 7.5 %), friability (less than M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. Table IV. Evaluation parameters of DXM oral disintegrating tablets Parameter WT (s) Water absorption ratio In vitro DT (s) Oral DT (s) A1 19.2 ± 0.4 82.69 ± 1.6 5.89 ± 1.2 26.7 ± 1.6 A2 65.3 ± 0.7 132.5 ± 1.8 19.2 ± 2.4 45.39 ± 2.7 A3 35.6 ± 0.8 116.7 ± 1.7 9.27 ± 1.9 32.56 ± 1.7 WT and DT represent wetting time and disintegration time, respectively. 1 %) and content uniformity of tablets (95100 %) of all batches (A1, A2 and A3) were found to be within the limits. Wetting time of A1 formulation of 19.2 ± 0.4 s was lower compared to A2 and A3 formulations (65.3 ± 0.6 and 35.6 ± 0.8 s, respectively) (Table IV). Faster wetting of A1 tablets containing Avicel PH 101 might be due to its rapid water absorbing nature involving both capillary and swelling mechanisms (20). Water absorption ratio, R, of formulations containing Pearlitol® SD 200 (132.5 ± 1.8) was higher than that of Avicel PH 101 and combination of Pearlitol® SD 200 and Avicel PH 101 (82.7 ± 1.6 and 116.7 ± 1.3, respectively) (Table IV). Formulation containing a higher amount of Pearlitol® SD 200 showed increased wetting and disintegration time. Increase in wetting and disintegration time may be due to the increase in polyol quantity in the tablet formulation. As polyols are readily soluble in water, there is a competition between spray-dried mannitol and CP for water penetrating into the tablet, consequently leading to poor swelling of CP with subsequent delay in disintegration. These results are consistent with the reports of Shagufta et al. (21). Taste evaluation and in vivo disintegration time Taste evaluation was performed on six healthy human volunteers and the results are given in Table V. Pure drug was felt bitter immediately after it was kept on the ton- Table V. Comparative taste evaluation Degree of bitterness after time Form of DXM 10 s Pure drug Drug resinate Unflavoured tablet with drug resinate Flavoured tablet with drug resinate 3 0 0 0+ 1 min 3 0 0 0+ 5 min 3 0.5 0 0+ 10 min 3 0 0 0+ Results are the mean of 6 observations. + indicates palatability. gue and the sense persisted up to 10 minutes. However, drug bitterness was masked af276 M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. ter its binding to the resin. Among the formulations tested, unflavoured tablets exhibited no bitterness even after 10 min whereas flavoured tablets exhibited palatability. Since the drug is not in the native form and is bound to the resin, reduced availability of free drug in the saliva could have led to the masking of the bitter taste. As regards wetting time, R value, in vitro DT, and cumulative drug released, formulations containing CP with Avicel pH 101 were considered to be better than those containing CP with Pearlitol® SD 200. A1 formulations showed lower DT with 5.9 ± 1.2 s compared to A2 and A3 (19.2 ± 2.4 and 9.3 ± 1.9, respectively). Complete in vivo disintegration was achieved within 26.7 ± 1.6 s for A1 formulation whereas it increased to 45.4 ± 2.7 and 32.6 ± 1.7 for A2 and A3 formulations (Table IV). Based on in vitro and in vivo disintegration, A1 was considered to be the optimal ODT formulation among all the formulations tested. In vitro release Based on the investigation, tablets of batch A1 were considered to possess the best physical properties accompanied with fast disintegration time. Therefore, to understand the dissolution behavior, the in vitro release study was conducted for optimized DXM oral disintegrating tablets (A1) and compared with the conventional, directly compressed DXM tablet that contains pure drug in place of drug-resin complex. Since ODT is meant to release the drug in stomach and the drug release from resinate is dependent on the exchange of hydrogen ions, the dissolution was conducted in simulated gastric fluid. The drug release from both formulations was almost 80 % within 60 min (Fig. 6). However, in case of A1 formulation, the drug release was 55 % in 10 min, which is higher compared to the drug release from the conventional tablet (40 %). The dissolution efficiency calculated was 70.9 and 63.8 % for optimized and conventional directly com- Cumulative drug release (%) 60 optimized conventional 40 Fig. 6. In vitro release profiles of optimized formulation (A1) and conventional tablet (mean ± SD, n = 6). 0 0 10 20 30 Time (min) 40 50 60 M. Malladi et al.: Design and evaluation of taste masked dextromethorphan hydrobromide oral disintegrating tablets, Acta Pharm. 60 (2010) 267280. pressed formulations, respectively. The optimized ODT dissolution behavior was almost comparable to the conventional tablet, which clearly demonstrates that drug is displaced from resinate without any delay in the dissolution process despite the fact that the drug is in complex with ion-exchange resin. Obviously, this could be due to free dissociation of the drug from resinate due to the exchange with hydrogen ions present in the dissolution medium. However, longer time was necessary for the drug to dissociate completely from the resinate. CONCLUSIONS The study has revealed the effect of particle size of resin on drug loading and release. The extent of drug loading and release were higher with small particle size resins compared to larger particle size resins. Characterization of the ODTs confirmed that adequate taste masking and faster disintegration could be achieved for the optimized (A1) formulation. Based on the results, it can be concluded that the bitterness of DXM can be masked with the resin and can be incorporated in ODTs with good dissolution behavior. Acknowledgments. The authors are grateful to CPS Formulations, DR. Reddy's Laboratories Ltd, India, for providing the gift sample of Dextromethorphan and for allowing the use of DSC, XRPD and FTIR and also thank Rohm and Haas, USA, for providing Amberlite IRP69 and Amberlite IRP 88.
Acta Pharmaceutica – de Gruyter
Published: Sep 1, 2010
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