Controlled-Release Matrix of Acetaminophen-Ethylcellulose Solid Dispersion

Development of novel fast-dissolving tacrolimus solid dispersion-loaded prolonged release tablet

The goal of this research was to develop a novel prolonged release tablet bioequivalent to the commercial sustained release capsule. A number of tacrolimus-loaded fast-dissolving solid dispersions containing various amounts of DOSS were prepared using the spray drying technique. Their solubility, dissolution and pharmacokinetics in rats were studied. DOSS increased drug solubility and dissolution in the solid dispersions. Compared with the drug powder, the solubility, dissolution and bioavailability of tacrolimus with the fast-dissolving solid dispersion containing tacrolimus/HP-β-CD/DOSS in the weight ratio of 5:40:4 were boosted by approximately 700-, 30- and 2-fold, respectively. Several tablet formulations were accomplished with this solid dispersion in combination with various ratios of HPMC/ethylcellulose. The release behaviour and pharmacokinetic studies in beagle dogs were assessed compared with the commercial prolonged release capsule. A decrease in HPMC/ethylcellulose ratios reduced the dissolution of tacrolimus from the tablets. Particularly, the tacrolimus-loaded prolonged release tablet consisting of fast-dissolving tacrolimus solid dispersion, HPMC, ethylcellulose and talc at the weight ratio of 20:66:112:2 exhibited a dissolution profile similar to that produced by the commercial prolonged release capsule. Furthermore, there were no significant differences in the AUC, Cmax, Tmax and MRT values between them in beagle dogs. Consequently, this tacrolimus-loaded prolonged release tablet might be bioequivalent to the tacrolimus-loaded commercial capsule.

Improved bioavailability of poorly water-soluble drug curcumin in cellulose acetate solid dispersion

Curcumin (Cur), one of the most widely used natural active constituents with a great variety of beneficial biological and pharmacological activities, is a practically water-insoluble substance with a short biologic half-life. The aim of this study was to develop a sustained-release solid dispersion by employing water-insoluble carrier cellulose acetate for solubility enhancement, release control, and oral bioavailability improvement of Cur. Solid dispersions were characterized by solubility, in vitro drug release, Fourier transform infrared spectroscopy, X-ray diffractometry, and differential scanning calorimetry studies. The in vivo performance was assessed by a pharmacokinetic study. Solid-state characterization techniques revealed the amorphous nature of Cur in solid dispersions. Solubility/dissolution of Cur was enhanced in the formulations in comparison with pure drug. Sustained-release profiles of Cur from the solid dispersions were ideally controlled in vitro up to 12 h. The optimized formulation provided an improved pharmacokinetic parameter (C(max) = 187.03 ng/ml, t(max) = 1.95 h) in rats as compared with pure drug (C(max) = 87.06 ng/ml, t(max) = 0.66 h). The information from this study suggests that the developed solid dispersions successfully enhanced the solubility and sustained release of poorly water-soluble drug Cur, thus improving its oral bioavailability effectively.

Development of a novel combination tablet containing trimebutine maleate and mosapride citrate for the treatment of functional dyspepsia

To develop a novel combination tablet which contained 100 mg trimebutine maleate and 5 mg mosapride citrate (TMCT) for the treatment of functional dyspepsia, the wet granulation method was used to prepare TMCTs with various amounts of diluents and stabilizers. The levels of impurities, the stability and the dissolution of the TMCTs were investigated. The oral bioavailability of drugs in the TMCTs was then evaluated and compared to the simultaneous oral administration of trimebutine maleate-loaded and mosapride citrate-loaded commercial products in the beagle dog. Among the diluents tested, D-mannitol was selected, since the microcrystalline cellulose and lactose did not inhibit the production of drug impurities due to their hygroscopic properties and chemical interactions, respectively. Furthermore, succinic acid was selected as the stabilizer because it gave the lowest level of total drug impurities of the organic acids tested. The combination tablet of trimebutine maleate and mosapride citrate prepared with D-mannitol and succinic acid gave a total drug content higher than 95% and total impurities lower than 0.5% at 25°C/60% RH and 40°C/75% RH during a 6-month period, indicating that the tablets were stable for at least 6 months. Furthermore, this combination tablet showed a similar dissolution to the trimebutine maleate-loaded and mosapride citrate-loaded commercial products and gave insignificantly different absorption compared to these commercial products in beagle dogs. Thus, the combination tablet of trimebutine maleate and mosapride citrate prepared with D-mannitol and succinic acid would be a stable and effective oral pharmaceutical product for the treatment of functional dyspepsia.

Formulation of sustained-release dosage form of verapamil hydrochloride by solid dispersion technique using Eudragit RLPO or Kollidon SR

The release of verapamil hydrochloride from tablets with Eudragit RLPO or Kollidon SR with different drug-to-polymer ratios were investigated with a view to develop twice-daily sustained-release dosage form by solid dispersion (SD) technique. The SDs containing Eudragit RLPO or Kollidon SR at drug-polymer ratios of 1:1, 1:2, and 1:3 with verapamil hydrochloride were developed using solvent evaporation technique. The physical mixtures of drug and both polymers were prepared by using simple mixing technique at the same ratio as solid dispersion. The physicochemical properties of solid dispersion were evaluated by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The study of DSC, XRD, and FTIR could not show significant interaction between verapamil HCl and Kollidon SR or Eudragit RLPO. The solid dispersions or physical mixtures were compressed to tablets. The tablets were prepared with solid dispersions containing Eudragit RLPO or Kollidon SR, with all the official requirements of tablet dosage forms fulfilled. Tablets prepared were evaluated for the release of verapamil hydrochloride over a period of 12 h in pH 6.8 phosphate buffer using US Pharmacopoeia type II dissolution apparatus. The in vitro drug release study revealed that the tablet containing Eudragit has extended the release rate for 12 h whereas the tablet containing Kollidon SR at the same concentration has extended the release rate up to 8 h. The in vitro release profile and the mathematical models indicate that release of verapamil hydrochloride can be effectively controlled from a tablet containing solid dispersions of Eudragit RLPO. The reduction of size fraction of the SD system from 200-250 to 75-125 microm had a great effect on the drug release.

High-amylose carboxymethyl starch matrices for oral sustained drug-release: In vitro and in vivo evaluation

High-amylose corn starch, that contains 70% of amylose chains and 30% of amylopectin, has been used to obtain substituted amylose (SA) polymers. Tablets have been prepared by direct compression, i.e. dry mixing of drug and SA, followed by compression, which is the easiest way to manufacture an oral dosage form. Until now, their controlled-release properties have been assessed only by an in vitro dissolution test. Amylose-based polymers are normally subject to biodegradation by alpha-amylase enzymes present in the gastrointestinal tract, but matrix systems show no significant degradation of tablets by alpha-amylase in vitro. High-amylose sodium carboxymethyl starch (HASCA) is an interesting excipient for sustained drug-release in solid oral dosage forms. In addition to the easy manufacture of tablets by direct compression, the results show that in vitro drug-release from an optimized HASCA formulation is not affected by either acidic pH value or acidic medium residence time. In addition, a compressed blend of HASCA with an optimized quantity of sodium chloride provides a pharmaceutical sustained-release tablet with improved integrity for oral administration. In vivo studies demonstrate extended drug absorption, showing that the matrix tablets do not disintegrate immediately. Nevertheless, acetaminophen does not seem to be the most appropriate drug for this type of formulation.

Formulation, release characteristics and bioavailability of novel monolithic hydroxypropylmethylcellulose matrix tablets containing acetaminophen

Effect of incorporating pharmaceutical excipients on the in vitro release profiles and the release mechanism of monolithic hydroxypropylmethylcellulose (4000 cps) matrix tablets (m-HPMC tablets) in terms of mimicking the dual drug release character of bi-layered Tylenol ER tablets was studied. We also compared the in vitro release profiles of optimized m-HPMC matrix tablet and Tylenol ER tablet in water, pH 1.2 gastric fluid, and pH 6.8 intestinal fluid, and in vivo drug bioavailabilities in healthy human volunteers. Acetaminophen was used as the model drug. The m-HPMC tablets were prepared using a wet granulation method followed by direct compression. Release profiles and swelling rates of m-HPMC tablets were found to be highly influenced by the types and amounts of pharmaceutical excipients incorporated. Starch 1500 (Prejel) and sodium lauryl sulfate (SLS) played a key role in determining the dissolution rate of m-HPMC tablets. Additional excipients, i.e., microcrystalline cellulose (Avicel PH101) and NaH2PO4 were used to tune the release profiles of m-HPMC tablets. The effect of pharmaceutical excipients on drug release from HPMC-based matrix tablets was found to be mainly due to a change in hydrophilic gel expansion and on physical interactions between the drug and HPMC. The optimized m-HPMC tablet with a balanced ratio of Prejel, SLS, Avicel PH101, and NaH2PO4 in the formulation showed dual release profiles in water, pH 1.2 gastric fluid, and pH 6.8 intestinal fluid in vitro. Dual release was defined as immediate drug release within few minutes followed by extended release over 8 h. The similarity factors of m-HPMC tablets and bi-layered Tylenol ER tablets were 79.8, 66.1, and 82.7 in water, gastric fluid and intestinal fluid, respectively, indicating the equivalence of the two release profiles. No significant in vivo bioavailability differences were observed in healthy human volunteers. The developed m-HPMC tablet with dual release characteristics can be easily prepared using a conventional high-speed tablet machine and could provide an alternative to commercially available bilayered Tylenol ER tablets.

Tableting of Eudragit RS and propranolol hydrochloride solid dispersion: effect of particle size, compaction force, and plasticizer addition on drug release

The application of a solid dispersion (SD) system of propranolol HCl and Eudragit RS was evaluated in the preparation of prolonged release tablets. The effects of SD size fraction, compaction force, and inclusion of plasticizers [namely diethylphtalate (DEP) and triethylcitrate (TEC)] on crushing strengths of matrices and release profile of drug were also investigated. The results showed that when compressed as a tablet, the SD system was more efficient in prolonging drug release than physical mixture. This effect was due to formation of much harder tablets of the SD system (crushing strength 8.5 kg) compared with those of physical mixtures (crushing strength 2.7 kg). All matrices of the SD system showed release rate patterns that were best described by the Higuchi equation. It was also shown that the rate of drug release decreased from 19.8% to 9.13% min(-1/2) as the SD size fraction decreased from 300-350 to 125-250 microm. However, further reduction of size fraction did not significantly affect tablet crushing strength and drug release rate. Increase in compaction force from 5 to 30 kN increased the crushing strength of matrices from 2.9 to 13.6 kg. However, the rate of drug release remained nearly unchanged beyond compaction pressure of 10 kN, indicating that crushing strength of matrices in the range of 8.5-13.6 kg did not affect drug release rate. The addition of 5% or 10% of either plasticizer (DEP or TEC) led to an increase in crushing strength of matrices and more retardation of drug release. This effect was more pronounced for higher concentrations of plasticizers. This effect was probably due to more plastic deformation of matrices under the compaction force, which helped matrices to retain their shape throughout the dissolution test.