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Chem. Pharm. Bull. 60(12) 1514–1521 (2012)
Regular Article
Vol. 60, No. 12
Design and Evaluation of an Economic Taste-Masked Dispersible Tablet of Pyridostigmine Bromide, a Highly Soluble Drug with an Extremely Bitter Taste Qunyou Tan,a,# Li Zhang,b,# Liangke Zhang,b Yongzhen Teng,b and Jingqing Zhang*,b a
Department of Thoracic Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University; Chongqing 400042, P. R. China: and b Medicine Engineering Research Center, Chongqing Key Laboratory of Biochemical & Molecular Pharmacology, Chongqing Medical University; Chongqing 400042, P. R. China. Received July 18, 2012; accepted September 25, 2012 Pyridostigmine bromide (PTB) is a highly soluble and extremely bitter drug. Here, an economic complexation technology combined with direct tablet compression method has been developed to meet the requirements of a patient friendly dosage known as taste-masked dispersible tablets loaded PTB (TPDPTs): (1) TPDPTs should have optimal disintegration and good physical resistance (hardness); (2) a low-cost, simple but practical preparation method suitable for industrial production is preferred from a cost perspective. Physicochemical properties of the inclusion complex of PTB with beta-cyclodextrin were investigated by Fourier transformed infrared spectroscopy, differential scanning calorimetry and UV spectroscopy. An orthogonal design was chosen to properly formulate TPDPTs. All volunteers regarded acceptable bitterness of TPDPTs. The properties including disintegration time, weight variation, friability, hardness, dispersible uniformity and drug content of TPDPTs were evaluated. The dissolution profile of TPDPTs in distilled water exhibited a fast rate. Pharmacokinetic results demonstrated that TPDPTs and the commercial tablets were bioequivalent. Key words
pyridostigmine bromide; taste-masked; dispersible tablet; inclusion complex; bioequivalence
British Pharmacopoeia defined dispersible tablets (DPTs) as the uncoated tablets or film-coated tablets intended to be dispersed in water before administration giving a homogeneous dispersion. DPTs usually disintegrate within three minutes when put in a small amount (5 to 10 mL) of liquid (clean water or milk). It is easy for caregivers to prepare and easy for sick children to take.1–3) It is well established that DPTs may be a good dosage form of choice for geriatric, pediatric, bedridden, traveler, soldier, nauseous or non-complient patients. DPTs can also give a new lease of life to an existing drug for line extension or/and patenting new dosage form. Up to now, pharmaceutical companies have marketed various types of dispersible dosage forms, such as Afeksin® by Actavis Ltd., Coartem® by Novartis and Medicines,1) Amotaks® by Polfa Tarchomin SA.4) Pyridostigmine bromide (PTB; C9H13BrN2O2; molecular weight 261.12; very soluble; c log P −3.1; Fig. 1), also called 3-(dimethylcarbamyloxy)-1-methylpyridinium bromide, functions as a reversible competitive carbamate type of acetylcholinesterase inhibitor. PTB has been used to treat myasthenia
Fig. 1.
gravis for many years.5) The indication for prophylaxis against intoxication with nerve agents (such as sarin and soman) has been recently approved by the U.S. Food and Drug Administration (FDA) and the French Drug Agency.6) So far, the formulations of PTB used clinically are the sugar-coated tablet, sustained release tablet, injection and syrup. DPT may be an appropriate alternative dosage form of PTB. However, PTB is a highly soluble drug with a bitter taste, and thus effectively taste masking is critical to patient compliance, and it is also the first and foremost challenging task in the preparation of DPT.7) In brief, in terms of PTB (a highly soluble drug with an extremely bitter taste), it is a big challenge to develop a tastemasked dispersible tablet (TPDPTs) suitable for industrial production. Here, economic complexation technology combined with direct tablet compression method has been developed to meet the requirements of TPDPTs: (1) TPDPTs should have optimal disintegration and good physical resistance (hardness); (2) low-cost, simple but practical preparation methods are preferred from a cost perspective.
The Chemical Structure of PTB (A) and βCD (B), and the Proposed Structure Model of PTBCD (C)
The authors declare no conflict of interest. # These authors contributed equally to this work. * To whom correspondence should be addressed.
e-mail:
[email protected]
© 2012 The Pharmaceutical Society of Japan
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Taste-masking technologies8) that have commonly been used in drug solid formulations, in general, include micronization,9,10) solid dispersion,11–13) and complexation.14) Betacyclodextrin (βCD) is a cyclic oligosaccharide composed of seven dextrose units joined through α-1,4-glucosidic bonds.15) Being a non-toxic and low-cost excipient with some favourable characteristics, βCD has been recorded in many national pharmacopoeias (such as United States Pharmacopoeia, Chinese Pharmacopoeia and Japanese Pharmacopoeia). It has been successfully used to improve the solubility, dissolution rate and bioavailability of poorly water-soluble drugs,16) enhance the physicochemical stability of unstable drugs17) and eliminate the undesired taste of the bitter drug.18–20) Regarding the application of βCD to mask the bitter taste of drugs, the effects of βCD on both the tablet hardness and disintegration time should be considered simultaneously: in general, tablet hardness increases with the increased amount of βCD, and the disintegration time increases with the increase in hardness.21) So, in order to produce taste-masked DPTs with optimal disintegration and good physical resistance (hardness), it is important to use effective disintegrants combined with suitable amounts of drug inclusion complexes with βCD. In the experiments, complexation technology was employed to develop an alternative drug delivery system with a favorable taste for PTB (a highly soluble drug with an extremely bitter taste) for increasing patient compliance and guaranteeing the effectiveness of the therapy. The objectives of this study were as follows: (1) PTB complexed with βCD (PTBCDs) were prepared by using the kneading method. Physicochemical properties of PTBCDs were investigated by Fourier transformed infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and UV (UV) spectroscopy. (2) Taste-masked PTB DPTs (TPDPTs) were prepared by direct compression, and a four-factor, three-level orthogonal design was chosen to properly formulate TPDPTs. (3) The properties including the bitter taste, disintegration time, weight variation, friability, hardness, dispersible uniformity and drug content of TPDPTs were Table 1.
Experimental
Materials PTB was obtained from Yuancheng Technology and Development Co., Ltd. (Wuhan, China). Lactose was kindly donated by Meggle Co., Ltd. (Bavaria, Germany). Microcrystalline cellulose (MCC), carboxymethyl starch sodium (CMS-Na) and low-substituted hydroxypropylcellulose (L-HPC) were obtained from Ahua Pharmaceutical Co., Ltd. (Liaocheng, China). Polyvinylpolypyrrolidone cross-linked (also called Crospovidone, PVPP) was obtained from Boai New Kaiyuan Pharmacy Co., Ltd. (Jiaozuo, China). Mannitol was obtained from Bright Moon Seaweed Group Co., Ltd. (Qingdao, China). Mint flavor was kindly donated by Firmenich Fragrance Co., Ltd. (China). Aspartame was obtained from Changmao Biochemical Engineering Co., Ltd. (Chaozhou, China). Commercial conventional PTB tablets were obtained from Shanghai Sanwei Pharmaceutical Co., Ltd. (Shanghai, China). Acetonitrile (HPLC grade) was obtained from Fisher Scientific U.K., Ltd. (Loughborough, U.K.). Other reagents were analytical grade and used as received. Preparation of PTBCDs The PTBCDs were prepared according to the kneading method reported previously.22,23) Weighed amounts of PTB and βCD with a 1 : 1 molar ratio were mixed with the dropwise addition of 5 mL of water to form a homogenous paste. The paste was further ground for 60 min and dried. The obtained mass was washed three times with absolute ethanol and the solvent was eliminated by vacuum evaporation at 55°C. The final product was pulverized and sieved with an 80 mesh filter. FT-IR Spectroscopy of PTBCDs The FT-IR spectroscopic experiments were carried out with a FT-IR spectrophotometer (Spectrum One NTS, PerkinElmer Instruments Inc., Massachusetts, U.S.A.). The samples (PTB, βCD, the physical mixture and PTBCDs) were compressed into KBr pellets and then scanned over the frequency range of 400–4000 cm−1. Differential Scanning Calorimetry (DSC) of PTBCDs The samples, sealed in the aluminum crimp cell, were heated at the speed of 10°C min−1 from 30 to 200°C under a nitrogen atmosphere.24) The phase transition onset temperatures of pure PTB, βCD, the physical mixture and PTBCDs were determined and compared with the help of a differential scanning calorimeter (Netzsch STA-449C, Selb, Germany). UV Spectroscopy of PTBCDs The complex formation composed of PTB and βCD in water was studied using the spectral shift method.25) The concentration of PTB was 180 µmol/L while the βCD concentration varied from 180 to 720 µmol/L (PTB and βCD with 1 : 0, 1 : 1, 1 : 2, 1 : 3, 1 : 4 molar ratios, respectively). The mixtures were kneaded for 1 h and the UV absorption spectra were recorded with a UV-3150 spectrophotometer (Shimadzu, Kyoto, Japan)
Optimal Formulation of TPDPTs
Ingredient (prescription analysis)
Content (%, w/w)
PTBCDs equivalent to 30 mg PB (principle or active agent) Anhydrous citric acid (effervescent disintegrants) Sodium bicarbonate (effervescent disintegrants) MCC (disintegrant and diluent) L-HPC (superdisintegrant) Talc (anti-adherent) Aspartame (sweetener) Menthol (sweetener) Mannitol (diluent)
Table 2.
evaluated. (4) The dissolution in vitro and pharmacokinetics in vivo were evaluated for the tested TPDPTs compared to the commercial tablets.
40 10 8 10 6 1 2 2 to 100
Factors and Levels of Orthogonal Design Factor
A (mg)
B
Level 1 Level 2 Level 3
20 40 60
PVPP CMS-Na L-HPC
A, amount of MCC; B, type of superdisintegrant; C, amount of superdisintegrant; D, amount of talc.
C (mg) 8 16 24
D (mg) 4 8 12
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Preparation of TPDPTs The TPDPTs containing the equivalent of 60 mg of PTB were compressed on a single rotary tabletting press (ZDY-8, Shanghai Far-east Pharmaceutical Machinery Co., Shanghai, China) using an 12-mm flat faced punch by direct compression. The PTB and excipients for 100 tablets were weighed according to the proportions listed in Table 1, and then passed through 80 meshes and blended to uniformity. The requisite quantity of the powder mixture was added into a die, and the pressure was adjusted to form the round tablets of hardness ca. 40 N. The tablet weight was adjusted to ca. 400 mg. Orthogonal Experimental Design (OED) Preliminary experimental results revealed that the factors of the amount of MCC (A, mg), kind of superdisintegrant (B), amount of superdisintegrant (C, mg), and amount of talc (D, mg) had relatively great influence on the disintegration time (T, s). Thus, a fourfactor, three-level OED was used to determine the optimal factors of the formulation for TPDPTs26,27) (Table 2). In order to study the influence of the tablet formulation on the disintegration time in vivo, TPDPTs with various formulations were prepared according to the orthogonal design (Table 3). The data was analyzed using the statistical package StatView, version 5.0 (SAS Institute, Inc., Cary, U.S.A.) Disintegration Time of TPDPTs The disintegration time was determined by Chinese Pharmacopoeia (CHP) 2010. Briefly, Six tablets were placed in a disintegration apparatus (ZB-lD, Taijin Tiandatianfa Scientific Co., Ltd., Tianjin, China). The core barrels were immersed in 1000 mL of water at 37±1°C, and kept moving up and down at 30–32 rpm. The disintegration time was recorded as the time when all granules passed through the sieve. The Taste Evaluation of TPDPTs The sensory evaluation was performed in 18 healthy volunteers (9 males and 9 females). Each volunteer was asked to wash his/her mouth well with distilled water prior to testing. Every tablet was dispersed in 10 mL of water before administration giving a homogeneous dispersion. One milliliter of the resulting dispersion was placed on the center of the tongue and retained in the mouth for 10 s, and then spat out. The bitterness was recorded according to the bitterness intensity scale: no bitterness, slight bitterness (slightly bitter but acceptable), and strong bitterness Table 3.
(strongly bitter and unacceptable). Reference conventional tablets (containing PTB instead of PTBCDs) were prepared by the method described above. Informed consents from the volunteers were first obtained. The trial in human was conducted according to the protocol approved and reviewed by the Institutional Ethics Committee. Dissolution Test of TPDPTs Dissolution studies were carried out with a dissolution apparatus (ZBR-6B, Huanghai Drug Examine Instrument Factory, Shanghai, China) according to the specifications of the CHP (2010 edition, paddle method). Dissolution flasks were immersed in 200 mL of distilled water at 37±0.5°C. The dissolution medium was continuously stirred at 100 rpm. The TPDPTs and the reference commercial tablet (SUNV®, conventional tablet) equivalent to 30 mg of PTB were added on the surface of the stirred dissolution medium. At different time intervals, 2 mL of samples were withdrawn and filtered using 0.22 µm cellulose nitrate membranes, and then analyzed by UV. Equal quantity of fresh distilled water was supplemented into the corresponding flasks. A similar factor ( f 2) method was investigated for dissolution profile comparison in our experiments.28) The f 2 value was calculated using the following formula (Eq. 1): f 2 = 50lg 1+ (1 / n)
−1/ 2 2 Wt ( X ii − X ri ) ×100 (1) i=1 where f 2 was the similar factor, X ii and X ri were drug cumulative release at time t of the two dissolution curves, respectively, n was the number of the sample point, Wt was the weight and set as 1 here. When the two profiles are identical, the f 2 value is equal to 100. In the case of an average difference of 10% at all sampling time points, the f 2 value changes to 50. The Food and Drug Administration (United States) has set a common criterion of f 2 value (50–100) to illustrate similarity between a pair of dissolution curves. The higher the value of a similar factor the closer the similarity. On the other hand, there is a significant difference between two curves when the f 2 value is below 50. The PTB concentrations were determined with a UV n
Results of Orthogonal Design (n=3)
Experiment number 1 2 3 4 5 6 7 8 9 k1 k2 k3 Δk
Factor A
B
C
D
1 1 1 2 2 2 3 3 3 72.24 54.45 76.84 22.39
1 2 3 1 2 3 1 2 3 69.54 73.48 60.52 12.96
1 2 3 2 3 1 3 2 1 78.18 63.19 62.17 16.01
1 2 3 3 1 2 2 3 1 62.69 67.15 73.69 11.00
T (s) 79.11±5.53 72.53±6.62 65.09±5.36 57.34±7.62 49.25±6.58 56.77±7.04 72.16±3.24 98.65±5.86 59.71±4.10
ki is the average scores of each factor at its different level (here, i equals to 1, 2, 3, respectively); Δk is the range among the average scores of each factor at its different levels. T is the disintegration time.
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spectrophotometer (UV-3150, Shimadzu, Kyoto, Japan). The calibration curve was linear in the range of 16–40 µg/mL (A=1.79×10−2C+6.5×10−3, r=0.9999, n=7; A means the absorbance of PTB at 269 nm, and C means the concentration of PTB). The recoveries of PB are (99.46±1.54)% (mean±S.D., n=9). The UV method provided an assay that was both sensitive and specific for quantifying PTB. Evaluation of Weight Variation, Friability, Hardness, Dispersible Uniformity and Drug Content of TPDPTs The TPDPTs were determined for weight variation, friability, hardness, dispersible uniformity and drug content as per the CHP (2010 edition) method of tablet evaluation. Briefly, (1) Twenty randomly selected tablets were weighed individually (Mettler Toledo, Greifensee, Switzerland). The average weight and the relative standard deviation were calculated. (2) Sixteen tablets (about 0.65 g) were accurately weighed and placed in the drum of friabilator (CJY-300C, Shanghai Huanghai Drug Inspection Instrument Co., Shanghai, China). The tablets were rotated at 25 rpm for 4 min. After 100 revolutions, the tablets were removed, carefully dedusted and accurately reweighed. The percentage of weight loss was calculated and the friability was evaluated. (3) The hardness (fracture strength) of TPDPTs was measured with a hardness tablet tester (YPJ-200A, Shanghai Huanghai Drug Inspection Instrument Co., Shanghai, China). (4) Dispersible uniformity of TPDPTs was determined as follows: six tablets were placed in 100 mL of distilled water at 15–25°C and shanked for 3 min. Each tablet should disintegrate within 3 min and pass through 24 meshes (the aperture size is (850±29) μm). (5) Twenty tablets were crushed and the powder equivalent to 30 mg of PTB was dissolved by distilled water, transferred into a 100 mL of volumetric flask, fixed and sonicated for 15 min. The resulting solution was filtered through a 0.45 µm microfilter and the filtrate was analyzed by the UV method described above. The drug content was then calculated. Preliminary Evaluation of Suspension Stability of TPDPTs DPTs are expected to disintegrate within 3 min in water, disperse into small granules, and eventually form a uniform suspension before administration. In case of a conventional suspension formulation, the suspension stability is often evaluated by the sedimentation rate method. However, this method is not suitable for DPTs due to the unclear sedimentation boundary. So, a simple and fast method (namely, light transmittance method) for the preliminary evaluation of the suspension stability of DPTs has been developed.29) The basic principles of the light transmittance method are based on two findings: (1) the light transmittance values are related with the sedimentation of the suspension formed by a dispersible tablet. (2) the change values of light transmittance have a linear correlation with the sedimentation time in the range of t (time)=0–30 min. The regression equation can be expressed as follows: (TRAt − TRA 0 ) / TRA 0 = Kt + b 0
(2)
where t refers to the sedimentation time, TRAt is the value of light transmittance determined at a certain time (t), TRA0 is the value of light transmittance determined at the beginning. K is the slope of the regression curve, b0 is the intercepts. The smaller the value of K is, the slower the suspension sedimentation is, and the higher the suspension stability is. In our experiments, six randomly selected tablets were
evaluated for the the suspension stability of TPDPTs using the light transmittance method. Briefly, each tablet was placed in 50 mL of distilled water and stirred until completely and evenly dispersed, followed by the determination of TRA at the wavelength of 700 nm at different times (0, 5, 10, 15, 20, 30 min). Then, the data were fitted according to the Eq. 2. Pharmacokinetics Study in Vivo Animal facilities and protocols were in accordance with the National Institute of Health’s guidelines regarding the principles of animal care (2004). To evaluate the effects of TPDPTs on the release profiles in vivo, 12 male New Zealand White (NZW) rabbits weighing 2.5–3.0 kg were used. In a single-dose, randomized, open-label, two-period crossover trial, all the rabbits were divided into two groups and fasted for overnight.26,30) The test TPDPTs were dispersed in 5 mL of water and immediately administered by gastric perfusion. The reference commercial tablets (SUNV®, conventional tablets) were placed in the pharynx, and swallowed whole with 5 mL of water. (By the way, the reason that the conventional PTB-loaded commercial tablet not PTB-loaded dispersible tablet was used as reference tablets in our study is because that no PTB-loaded dispersible tablet is available on the market, it has been neither reported.) The concentrations of PTB from the rabbits at the predetermined timepoints post-administration were measured by HPLC.31,32) The peak concentration (Cmax) and peak time (Tmax) were derived directly from the concentration–time curve. The other pharmacokinetic parameters were calculated using the DAS 2.1.1 statistical software (Mathematical Pharmacology Professional Committee of China, Shanghai, China). A 1.0 mL aliquote of ear vein blood was collected from the rabbits at the predetermined time points after dosing. The plasma samples obtained from the upper layer after centrifugation (15 min, 1500 rpm) were stored at −80°C until HPLC analysis.33) The plasma samples were pre-treated as follows: a 100 µL aliquot of internal standard solution (Prostigmin, 208 µg·mL−1), 200 µL of picric acid (0.1 M) in 0.1 M sodium hydroxide (pH adjusted to 7), and 1.0 mL of water-saturated dichloromethane was added to each plasma sample (100 µL). The resulting mixture was vortexed for 3 min and then centrifuged at 12000 rpm for 10 min. After 200 µL of tetrabutyl ammonium bromide (1 m M) was added to the solution below, this mixture was shaken for 1 min and centrifuged at 12000 rpm for 5 min. Aliquots of the supernatant were injected into the HPLC system for further analysis. The plasma concentrations of PTB were determined by using the reversed-phase HPLC (Shimadzu System). The stationary phase (Hypersil ODS-2 column, 250 mm×4.6 mm, 5 µm) was kept at 30°C. The mobile phase was a mixture, with ratio of acetonitrile : aqueous buffer (10 m M sodium dihydrogen phosphate, 10 m M sodium heptanesulfonate, 0.5% triethylamine)=20 : 80 (v/v, pH adjusted to 3.0 with phosphoric acid). The flow rate was 1.0 mL/min. The sample injection volumes were 20 µL and PTB detection was performed using the UV detector at a wavelength of 270 nm. The calibration curve was linear in the range of C=20–2000 ng/mL (Y=0.5500C+0.07546, r=0.9996, n=7; Y means the peak area ratio between PTB and prostigmin). The limit of detection (LOD) was 5 ng/mL. The HPLC method provided an assay that was both sensitive and specific for quantifying PTB.
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Fig. 3. DSC Thermograms of βCD (a), PTB (b), Physical Mixture (c) and PTBCDs (d)
Fig. 2. FT-IR Spectra of βCD (a), PTB (b), Physical Mixture (c) and PTBCDs (d)
Results and Discussion
FT-IR Spectroscopy of PTBCDs The FT-IR spectra of PTB, βCD, physical mixtures and PTBCDs in the transmittance mode were depicted in Fig 2. The peaks of βCD at 3403 cm−1, 2923 cm−1, 1657 cm−1, 1158 cm−1 and 1081 cm−1 were assigned to the O–H stretching vibrations, the C–H stretching vibrations,34) the H–O–H bending vibrations, the C–O stretching vibration and the C–O–C stretching vibration, respectively. The peaks of PTB at 2945 cm−1, 3044 cm−1, 1000–1200 cm−1, 1200–1500 cm−1 and 1734 cm−1 were assigned to the C–H stretching vibration of the methyl group, the C–H stretching vibration of pyridine ring, the C–N stretching vibration of the tertiary amine, the skeleton vibration of the pyridine ring and C=O stretching vibration of the ester carbonyl, respectively. The FT-IR spectrum of the physical mixtures showed overlapping effects of PTB and βCD, accompanying with the attenuation of the PTB peaks. However, in the spectrum of PTBCDs, the characteristic peaks of βCD remain strong while the peaks of PTB almost disappear. The results suggested the modification of the drug environment and that the guest molecules (PTB) were entrapped inside the cavities of the host moleculars (βCD) through forming an
inclusion complex. These FT-IR spectroscopy change phenomena happened to the PTBCDs were similar to what happened to the simvastatin/hydroxypropyl-βCD inclusion complex reported by Jun et al.35) Differential Scanning Calorimetry (DSC) of PTBCDs It was believed that the DSC spectra could be used for the recognition of the inclusion complex.36) When the guest molecules were embedded into the cavity of the host molecules (βCD), their melting or boiling points generally disappeared or shifted to a different temperature. In our study, the thermograms of PTB, βCD, physical mixture and the inclusion complex were depicted in Fig. 3. Pure βCD showed a broad endothermic peak at 70.2°C, as corresponding to the dehydration process. The free PTB showed a sharp endothermic peak at 153.3°C, as corresponding to the melting point of the drug. The DSC curve of the physical mixtures mainly showed overlapping effects of PTB and βCD, accompanying with the reduction of the PTB peak, while the DSC curve of the PTBCDs showed that the characteristic endothermal peak of PTB disappeared, indicating the inclusion of PTB into βCD cavity. UV Spectroscopy of PTBCDs The effect of βCD on the UV absorption of PTB in the aqueous solution was showed in Fig. 4. PTB alone in aqueous solution exhibited one absorption peak at 269 nm, while the UV absorption of βCD alone in aqueous solution was negligible at 200–400 nm. No red shift or blue shift of the UV absorption spectra was observed when
Fig. 4. UV Spectra of PTB in the Presence of βCD in Different Molar Ratio (A) and the Profiles of Absorbance at 269 nm against the Concentration of βCD (B)
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Table 4. Properties of TPDPTs Prepared Under the Optimal Conditions (Mean±S.D., n=3) Properties
Batch 1
Batch 2
Batch 3
Disintegration time (s) Weight uniformity (mg) Friability (%) Hardness (N) Content uniformity (%) Slope K (×10−2)
48.5±4.76
49.2±3.60
48.2±2.64
406.34±1.55
409.13±2.24
402.77±0.87
0.52 40 97.55±0.43
0.50 40 99.46±0.75
0.47 40 99.64±0.93
1.09
1.13
Table 5.
Results of Taste Evaluation
Bitterness test No bitterness Slight bitterness Strong bitterness
The number of volunteers TPDPTs 12 6 0
Conventional tablets 0 1 17
1.06
Slope K is the slope of the regression curve (see the regression Eq. 2).
Fig. 6. PTB Plasma Concentration versus Time Profiles after Oral Administration of TPDPTs and the Commercial Tablets (n=12)
Fig. 5. The Dissolution Profiles of the TPDPTs and the Reference Commercial Tablet (n=6)
different amounts of βCD were added into the PTB solution. The absorbance of PTB at 269 nm decreased gradually with the addition of βCD. The more βCD was added, the lower the absorbance of PTB was obtained. The profiles of absorbance at 269 nm against the concentration of βCD (Fig. 4B) indicated that the PTB absorbance decreased with the increase of the βCD concentration in a linear fashion (the correlation coefficient value was 0.9887). These absorbance changes suggested the chromophore groups of PTB might be partially masked by βCD through the inclusion complextion.25) The UV results, considering together with the above described DSC and FT-IR profiles, indicated that PTB molecules might get into and remain in the βCD cavities (Fig. 1C). The bitter taste of PTB might be caused by the dimethylcarbamyloxy group since the bitter taste decreased or masked upon complexation of PTB with βCD (data not shown). Certainly, more efforts might be needed to testify this hypothesis about the mask mechanism. Preparation of TPDPTs Several process parameters (such as methods of preparation, hardness and size of the die)and compositions of tablets (such as diluents and disintegrants) were screened with a single factor design in the preliminary experiments (data not shown). After that, four critical factors (including the amount of talc, the amount of MCC, the amount of superdisintegrant, and the type of superdisintegrant) which had relatively great influence on the disintegration time were optimized using an orthogonal design. Taking the talc as an example, punch sticking usually happened when the recipe
contained a substantial of βCD. To prevent the punch from sticking, talc (as an effective anti-stick agent) was added into the formulation. However, excessive talc with very low water solubility would prevent water from infiltrating and wetting the tablet, and consequently prolonged the disintegration time. It was very important to use the right amount of talc. The function of each ingredient in the formulation was analysised (Table 2). Apparently, the best formulation had the shortest disintegration time. As shown in Table 3, the optimal levels of formulation were found to be A 2B3C3D1, that is, the optimal values for the amount of MCC (A, mg), the kind of superdisintegrant (B), the amount of superdisintegrant (C, mg), and the amount of talc (D, mg) should be 40 mg, L-HPC, 24 mg and 4 mg, respectively. Particularly, our study suggested that MCC (disintegrant and diluent) should be used in combination with L-HPC (superdisintegrant) to obtain the rapidly disintegrating tablet with a short disintegration time. Similar results were reported in former documents.37,38) The disintegration time of three batches of TPDPTs prepared under the above described optimal protocol (Table 1) was recorded as (48.63±0.51) s (Table 4). Other properties of three batches of TPDPTs prepared under the optimal conditions were also presented in Table 4. Characterization of TPDPTs The properties like weight variation, friability, hardness, dispersible uniformity drug content, and suspension stability of TPDPTs of three batches were found to be within acceptable limits (Table 4). An attempt had been made to mask the bitterness of PTB in TPDPTs by complexing it with βCD and combining the resultant complex with flavoring agents. As shown in Table 5, all volunteers regarded acceptable bitterness of TPDPTs but only about 5% of volunteers thought so in the case of conventional tablets (reference tablets). The dissolution profiles of the TPDPTs and the reference commercial tablet (SUNV®, conventional tablet) were depicted in Fig. 5. About (80.27±0.97)% (n=6) of the
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Vol. 60, No. 12 The Main Pharmacokinetical Parameters of TPDPTs and the Commercial Tablets (Mean±S.D., n=12) Parameters −1)
Cmax (mg·L Tmax (h) t1/2 (h) AUC0–24 (mg·h·L−1) AUC0–∞ (mg·h·L−1)
TPDPTs 1.83±0.08 2.33±0.41 3.44±0.63 15.50±0.62 15.82±0.70
drug in TPDPTs were released in the first 5 min, indicating that TPDPTs could be dissoluted in the distilled water at 37°C immediately. As for the reference commercial tablet, under the same conditions, only (7.51±1.30)% (n=6) was released. The dissolution profile of TPDPTs exhibited a faster rate of PTB compared with that of the reference commercial tablet. The difference between the curves of TPDPTs and the reference commercial tablet was statistically significant (the f 2 value was below 50). Pharmacokinetics and Bioequivalence Study in Vivo As shown in Fig. 6, the mean PTB plasma concentration–time profiles after oral administration of TPDPTs and the reference commercial tablet (SUNV®, conventional tablet) were comparable and exhibited closely similar pattern. The reasons for similar plasma exposure profiles of the two formulations are listed as follows: PTB, belongs to biopharmaceutics classification system (BCS) III, has low permeability and high solubility. The absorption is limited by the permeation rate, but the drug solvates very fast. Compared to the commercial tablets, the test TPDPTs do not change the PTB permeability or the gastro-intestinal duration time much under the experimental condition, so the plasma exposure profiles of two formulations are similar. However, it should be noted that there were still a few differences between the plasma exposure profiles of two formulations. For example, the Cmax and Tmax of TPDPTs were higher than that of the commercial conventional tablets. Pharmacokinetic parameters and 90% confidence intervals were listed in Table 6. The values (AUC0–24, AUC0–∞ and Cmax) were within the bioequivalence range of 80–125%. Tmax of the two formulations were not significantly different (p>0.05) when using the Wilcoxon rank sum test. The results demonstrated that PBODTs and commercial tablets were bioequivalent. The relative bioavailabilities of F0–24 and F0–∞ were 102.38% and 106.61%, respectively.
Conclusion
In the present work, a patient friendly dosage form known as PTB-loaded dispersible tablets with desirable taste, short disintegrating time, fine dispersible uniformity and rapid dissolution rate were successfully prepared using inclusion complexation technology in combination with the direct compression method. TPDPTs and the commercial tablets are bioequivalent. TPDPTs may be a very promising candidate for drug delivery and have good market prospects. Acknowledgements This research was partially supported by Grants from the National Natural Science Foundation of China (No. 30973645), Specialized Research Fund for the Doctoral Program of Higher Education (20095503120008), Chongqing Natural Science Foundation (CSTC2012JJB10027), and Chongqing Education Committee Fund (Excellent
Commercial tablets 1.68±0.03 2.58±0.20 3.95±0.34 15.14±0.30 15.57±0.32
90% Confidential interval 102.53–116.01%
98.37–106.19% 97.40–105.87%
university personnel financial aid plan, KJ120321). The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
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