Continuous flow bead-bed dissolution apparatus for suppositories

Comparison of three dissolution apparatuses for testing calcium phosphate pellets used as ibuprofen delivery systems

Porous calcium phosphate pellets were produced according to two granulation processes (low and high shear wet granulations) and drug loaded with five ibuprofen contents (1.75%, 7%, 12.5%, 22%, and 36%) in order to ensure both bone defect filling and local drug delivery. The drug-release kinetics from the two types of pellets was studied using three dissolution apparatuses: paddle apparatus, reciprocating cylinder, and flow-through cell. The paper compared the three dissolution methods and considered the effect of the granulation process on the ibuprofen-release kinetics. Dissolution data were analyzed using the Weibull function as well as the difference (f1) and similarity (f2) factors. Dissolution kinetics was not influenced by the granulation process, regardless of the dissolution apparatus and of the drug content. The comparison of the three dissolution devices indicated that ibuprofen was released faster from granules loaded with 36% of drug content with the reciprocating apparatus, due to the disintegration of the granules occurring during the dissolution test. For the other drug contents, dissolution profiles were not significantly different from one apparatus to another. However, the flow-through cell seemed to be more suitable for the drug-release study of implantable materials.

W/O/W multiple emulsions containing nitroimidazole derivates for vaginal delivery

The aim of our study was to formulate a stable multiple emulsions containing two nitroimidazole derivates, metronidazole (MT) and ornidazole (OR), for vaginal therapy. MT and OR were located internal and external phases of multiple emulsion, respectively, and the in vitro release studies were realized in phosphate (pH 7) and lactate buffer (pH 4.5) solutions to investigate better the effect of pH and location of active substance on the release. The imaging studies were realized in rabbits following labeling MT and OR with Technethium-99m ((99m)Tc) to evaluate the in vivo absorption characteristics. The percentage of MT and OR released from the multiple emulsions in alkaline media were 3.2- and 2.8-fold greater than that observed in acidic media, respectively, when they were introduced in the internal phase of the multiple emulsions. The absorption rate of MT from vaginal epithelium was faster than OR. We observed that especially in alkaline medium a high release was found that was convenient for the vaginal infections seen in the alkaline pH. We concluded that W/O/W multiple emulsions were locally effective in vagina and they could be introduced as a new drug carrier system for vaginal delivery.

Inclusion Complex Formation of Water- Soluble Drug, Captopril, and Peracetylated-β-Cyclodextrin in Supercritical CO2 for Controlled Release Applications

The inclusion complex of CO2-soluble peracetylated-β-cyclodextrin (PAc-β- CD), heptakis(2,3,6-tri-O-acetyl)-β-cyclodextrin, and highly water-soluble drug captopril, was prepared by a chemical solvent-free method using supercritical carbon dioxide. The captopril-PAc-β-CD inclusion complex was further confirmed by DSC and XRD studies. In- vitro release of captopril from an oily suspension confirmed that the dissolution rate of captopril was much retarded from the inclusion complex as a result of the hydrophobic properties of PAc-β-CD.

Supercritical Carbon Dioxide Assisted Impregnation of Molsidomine into Poly(DL-Lactide-co-Glycolide) for Sustained Release Applications

Supercritical carbon dioxide (scCO2) was used as a processing medium for the fabrication of drug encapsulated poly(DL-lactide-co-glycolide) (PLGA) monoliths for their potential application in the controlled release of water soluble drugs. Exposure of PLGA to scCO2 leads to effective plasticization and liquefaction due to the high solubility and interaction of the scCO2 in the copolymer. By exploiting this property, it was demonstrated that prolonged release formulations of molsidomine, a peripheral nitrovasodilator used to treat angina pectoris, can be prepared by chemical solvent-free, scCO2 assisted drug impregnation method. The in-vitro dissolution studies revealed that the release rates of drug from the porous polymer monoliths containing different amount of the drug samples were significantly retarded due to encapsulation of molsidomine into the PLGA matrix.

Development pharmaceutics of microbicide formulations. Part II: formulation, evaluation, and challenges

In recent years, AIDS and sexually transmitted diseases (STDs) have become a burgeoning problem and are spreading at an alarming rate. Microbicides are being developed as a new therapeutic category for prevention of transmission of sexually transmitted infections (STIs) and HIV. Many of the microbicide formulations (MF) may fail to elicit a protective response either because of a lack of efficacy or inadequate formulation. Manufacturing a stable, efficacious, safe, and optimal product is the main objective of formulation development programs. Preformulation parameters (PP), as discussed in Part I of this series, influence formulation development significantly and should be considered carefully before designing a formulation strategy. Initially, based on PP and market research, a target product profile (TPP) is generated, which defines product attributes that can be normally classified as "essential" and "desirable." A complex and dynamic process begins thereafter that takes into consideration myriad factors starting from selection of delivery system, selection of excipients, compatibility study, prototype composition, selection of process and optimization, stability testing, scale up, manufacturing under good manufacturing practices (GMP), and packaging development. Prototype formulations are evaluated for several performance characteristics (e.g., dispersion behavior, bioadhesion, retention, spreading, rheology). These compositions are also subjected to biologic evaluation by various in vitro and in vivo models. Such a well-planned, well-coordinated, and well-implemented formulation development program not only accelerates overall development but also minimizes failures in subsequent clinical development studies. The objective of this review is to highlight the importance of formulation science, outline the steps involved in this process, and explore how these can be exploited for achieving optimal MF.

Effects of absorption enhancers in chloroquine suppository formulations: I. In vitro release characteristics

The need to develop chloroquine suppository formulations that yield optimal bioavailability of the drug has been emphasized. This study demonstrates the effects of incorporation of known absorption-enhancing agents (nonionic surfactants and sodium salicylate) on the in vitro release characteristics of chloroquine from polyethylene glycol (1000:4000, 75:25%, w/w) suppositories. The release rates were determined using a modification of the continuous flow bead-bed dissolution apparatus for suppositories. Results showed that the extent of drug release from suppositories containing any of three surfactants (Tween 20, Tween 80 and Brij 35) was 100%, whereas 88% release was obtained with control formulation (without enhancer) (P<0.05). However, Tween 20 was more effective than Brij 35 and Tween 80 in improving the drug release rate. There was a concentration-dependent effect with Tween 20, and 4% (w/w) of this surfactant was associated with the highest increase in the rate of drug release from the suppositories. Sodium salicylate at a concentration of 25% (w/w) also significantly enhanced the drug release rate, but a higher concentration of the adjuvant markedly reduced both the rate and extent of drug release. Combined incorporation of Tween 20 and sodium salicylate did not significantly modify (P0.05) the rate of drug release when compared to the effect of the more effective single agent. Due to their effects in improving the drug release profiles coupled with their intrinsic absorption-promoting properties, it is suggested that incorporation of 4% (w/w) Tween 20 and/or 25% (w/w) sodium salicylate in the composite polyethylene glycol chloroquine suppository formulations, may result in enhancement of rectal absorption of the drug. This necessitates an in vivo validation.

The release of isoconazole nitrate from different suppository bases: in-vitro dissolution, physicochemical and microbiological studies

The influence of the suppository base on the in-vitro release of isoconazole nitrate was studied by dissolution, physicochemical diffusion and microbiological disk-diffusion methods. Vaginal suppository formulations containing 25 mg isoconazole nitrate for local treatment of vaginitis were prepared by a fusion method, using different hydrophilic and lypophilic suppository bases (PEG 6000, PEG 4000, PEG 1500, Witepsol H15, Novata BD and Cremao). In-vitro release rates were examined by dissolution, physicochemical diffusion and microbiological disk-diffusion methods. In the physicochemical investigations the pH indicators (pH 1-14) erythrosin B, thymol blue, bromocresol green, chlorophenol red, phenol red, and alkali blue were added to agar gels. The discs were placed onto the agar gels and 21 h later, the coloured zone diameters were measured. In the microbiological investigations, the discs were put on the inoculated plates with the suspension of Candida albicans (Institute Pasteur 628). The inoculated plates were incubated at 37 degrees C for 3 days, then the diameters of inhibition zones were measured. In the dissolution investigations release rates were in the order PEG 6000 > PEG 4000 > PEG 1500 > > Witepsol H15 > Cremao > Novata BD. The diffusion distance of isoconazole nitrate in the physicochemical investigation was in the order polyethylene glycols > Witepsol H15 > Novata BD. In the microbiological studies release rates were found with polyethylene glycols > Witepsol H15 > Novata BD > Cremao. The findings in the in-vitro studies suggested that polyethylene glycols are suitable bases for vaginal suppositories.

Sustained release of buserelin acetate, a luteinizing hormone-releasing hormone agonist, from an injectable oily preparation utilizing ethylated beta-cyclodextrin

The possible use of heptakis (2,6-di-O-ethyl)-beta-cyclodextrin (DE-beta-CyD) as a parenteral sustained-release carrier for buserelin acetate, a luteinizing hormone-releasing hormone superagonist, has been examined. The in-vitro release of buserelin from the oily suspension was significantly retarded by the complexation with DE-beta-CyD, mainly due to the poor water solubility of the complex. A single subcutaneous injection of the suspension containing the buserelin-DE-beta-CyD complex to rats provided an effective continuous plasma level of buserelin lasting for at least one month, indicating a potential therapeutic efficacy for the treatment of the endocrine-dependent diseases. These results suggest that DE-beta-CyD serves as an injectable sustained-release drug carrier suitable for chronic treatment with buserelin acetate.

Improvement of dissolution and suppository release characteristics of flurbiprofen by inclusion complexation with heptakis(2,6-di-O-methyl)-beta-cyclodextrin

The inclusion behavior of methylated beta-cyclodextrins, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis-(2,3,6-tri-O-methyl)-beta-cyclodextrin in solution and the solid state was compared with that of natural beta-cyclodextrin using an anti-inflammatory drug, flurbiprofen, as a guest molecule. Stability constants were determined by the solubility method at various temperatures, and the thermodynamic parameters were calculated for inclusion complex formation in aqueous solution. The solid complexes were obtained in a molar ratio of 1:1, and their dissolution behavior and release from suppository bases were examined. The data suggest that the inclusion mode of the complex with 3 is somewhat different from that of the complexes with 1 and 2. From a practical point of view, 2 seems to be particularly useful for improving the pharmaceutical properties of flurbiprofen in various dosage forms.