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Physiologically-based biopharmaceutics modeling (PBBM) has potential to accelerate the development of new drug and formulations. An important application of PBBM is for special populations such as pediatrics that have pharmacokinetics dependent on the maturation process. Lamotrigine (LTG) is a Biopharmaceutics Classification System (BCS) II drug and is widely prescribed. Therefore, the goal of this study was to assess the biopharmaceutics risk of the low-soluble drug LTG when the ontogeny on gastrointestinal tract (GIT) physiological parameters are considered. An oral physiologically-based pharmacokinetic model and a PBBM were developed and verified using GastroPlus™ software for both adults and children (2-12 years old, 12-52 kg). The biopharmaceutics properties and GIT physiological parameters were evaluated by sensitivity analysis. High doses were simulated assuming a worst case scenario, that is, the dose of 200 mg for adults and 5 mg/kg (up to the maximum of 200 mg) for 2-year-old children. Although several authors have suggested that ontogeny may have an effect on gastrointestinal fluid volume, our study found no evidence of interference between fluid and dose volumes with in vivo dissolution of LTG. The most impactful parameter was found to be the gastric transit time. Therefore, the hypothesis is developed to examine whether LTG exhibits characteristics of a BCS II classification in vitro while showing BCS I-like behavior in vivo. This hypothesis could act as a base for conducting novel studies on model-informed precision dosing, tailored to specific populations and clinical conditions. In addition, it could be instrumental in assessing the influence of various release profiles on in vivo performance for both adult and pediatric populations.

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Pediatric drugs knowledge still leaves several gaps to be filled, all the while many biopharmaceutic properties applied to adults do not work in pediatrics. The solubility in many cases is extrapolated to pediatrics; however, sometimes it may not represent the real scenario. In this context, the aim of this study was to assess the possibility of the extrapolation of the solubility data assumed for adults to children aged 2-12 years using lamotrigine (LTG) as a model. LTG showed that its solubility is dependent on the pH of the medium, no precipitate formation was seen, and biomimetic media showed a greater capacity to solubilize it. Based on the dose number (D0 ) in adults, the LTG was soluble in acidic pH media and poorly soluble in neutral to basic. Similar behavior was found in conditions which mimic children aged 10-12 years at a dose of 5 and 15 mg/kg. The D0 for 5-year-old children at a dose of 15 mg/kg showed different behaviors between biorelevant and pharmacopeial buffers media. For children aged 2-3 years, LTG appeared to be poorly soluble under both gastric and intestinal conditions. Solubility was dependent on the volume of fluid calculated for each age group, and this may impact the development of better pharmaceutical formulations for this population, better pharmacokinetic predictions in tools as PBPK, and physiologically-based biopharmaceutics modeling, greater accuracy in the justifications for biowaiver, and many other possibilities.

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Thermosensitive bioadhesive formulations can display increased retention time, skin permeation, and improve the topical therapy of many drugs. Acne is an inflammatory process triggered by several factors like the proliferation of the bacteria Propionibacterium acnes. Aiming for a new alternative treatment with a natural source, propolis displays great potential due to its antibiotic, anti-inflammatory, and healing properties. This study describes the development of bioadhesive thermoresponsive platform with cellulose derivatives and poloxamer 407 for propolis skin delivery. Propolis ethanolic extract (PES) was added to the formulations with sodium carboxymethylcellulose (CMC) or hydroxypropyl methylcellulose (HPMC) and poloxamer 407 (Polox). The formulations were characterized as rheology, bioadhesion, and mechanical analysis. The selected formulations were investigated as in vitro propolis release, cytotoxicity, ex vivo skin permeation by Fourier Transform Infrared Photoacoustic Spectroscopy, and the activity against P. acnes. Formulations showed suitable sol-gel transition temperature, shear-thinning behavior, and texture profile. CMC presence decreased the cohesiveness and adhesiveness of formulations. Polox/HPMC/PES system displayed less cytotoxicity, modified propolis release governed by anomalous transport, skin permeation, and activity against P. acnes. These results indicate important advantages in the topical treatment of acne and suggest a potential formulation for clinical evaluation.

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Hypericin (Hyp), a natural hydrophobic and photoactive pigment, and methylene blue (MB), a hydrophilic cationic dye, are utilized as photosensitizer (PS) for photodynamic therapy of cancer. Bioadhesive and thermoresponsive polymeric systems can improve the drug availability by increasing the contact time between the system and the mucosa and also controlling the drug release. In this work, an accelerated physicochemical stability study of binary polymeric systems composed of poloxamer 407 (Polox) and Carbopol 934 P (Carb) for MB or Hyp release was performed. Formulations were prepared containing Polox (20%, w/w), Carb (0.15%, w/w) and MB (0.25%, w/w) or Hyp (0.01%, W/W) and submitted to different stress conditions (5 ± 3 °C, 25 ± 2 °C and 40 ± 2 °C with relative humidity of 75 ± 5%) during 180 days. The samples were analyzed as macroscopic characteristics, photosensitizer content and mechanical properties by texture profile analysis. Both systems displayed decrease of photosensitizer content less than 5% during 180 days. MB-system showed an undefined reaction model, while Hyp-system displayed PS decay following a pseudo first-order reaction. Systems also displayed stable mechanical characteristics. The pharmaceutical analyses showed the good physicochemical stability of the bioadhesive platform for delivery Hyp and MB in photodynamic therapy.

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Hypericin (Hyp) is a natural photoactive pigment utilized in the treatment of different types of cancer and antimicrobial inactivation using photodynamic therapy (PDT). Hyp is poorly soluble in water leading to problems of administration, getting close contact with the site, and bio-availability. Therefore, this study aimed to develop bioadhesive thermoresponsive system containing Hyp for local PDT. Carbomer 934P, poloxamer 407, and Hyp were used to prepare the thermoresponsive bioadhesive formulations. They were characterized for sol-gel transition temperature, mechanical, mucoadhesive, rheological (continuous flow and oscillatory) and dielectric properties, syringeability, in vitro Hyp release kinetics, ex vivo permeability, and photodynamic activity. The formulations displayed suitable gelation temperature and rheological characteristics. The compressional, mechanical and mucoadhesive properties, as well the syringeability showed the easiness of administration and the permanence of the system adhered to the mucosa or skin. The dielectric analysis helped to understand the Hyp availability, and its release presented an anomalous behavior. The system did not permeate the pig skin nor rat intestine and showed good biological photodynamic activity. Therefore, data obtained from the bioadhesive system indicate a potentially useful role as a platform for local hypericin delivery in PDT, suggesting it is worthy of in vivo evaluation.

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Polycarbophil is widely used in a variety of pharmaceutical formulations, mainly for their strong ability to adhere to the epithelial and mucous barriers (bio/mucoadhesion). On the other hand, its association with the thermoresponsive polymer (poloxamer 407) has been poorly explored. This work investigates the rheological, mechanical and mucoadhesive properties of polymer blends containing polycarbophil and poloxamer 407, in order to select the best formulations for biomedical and pharmaceutical applications. Mechanical (hardness, compressibility, adhesiveness, softness, and mucoadhesion) and rheological characteristics (consistency index, yield value and hysteresis area) showed that 20% (w/w) poloxamer 407- polymer blends exhibited higher values parameters. However, the rheological interaction parameter, which was more sensible than the mechanical interaction parameter, revealed higher synergism for systems comprising 15% (w/w) poloxamer 407, due to the system organization and polymers' properties. Furthermore, gelation temperatures were appropriated, suggesting that polymer blends can be used as biomedical materials, and displaying easy administration, enhanced retention and prolonged residence time at the site of application. Therefore, rheological, mechanical and mucoadhesive characterization provided a rational basis for selecting appropriated systems, useful for mucoadhesive drug delivery systems and biomedical applications.

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This study describes the investigation about the physicochemical behavior of methylene blue (Mb) addition to systems containing poloxamer 407 (Polox), Carbopol 934P (Carb), intended to be locally used by photodynamic therapy. A factorial design 23 (plus center point) was used to analyze the rheological, mucoadhesive and textural properties of the preparations. Systems containing the lower concentrations of Polox (15 and 17.5%, w/w) exhibited pseudoplastic flow and low degrees of rheopexy. On the other hand, at higher Polox concentration (20%, w/w) the systems display plastic flow and thixotropy. Carb and Mb exhibited a negative influence for the consistency and flow behavior index, due to the interaction between them. For most of the formulations, the increase of Polox and Mb content significantly increased storage modulus, loss modulus and dynamic viscosity. The systems display a sol-gel transition temperature, existing as a liquid at room temperature and gel at 29-37 °C. Increasing the temperature and the polymer concentration, the compressional properties of systems significantly increased. The mucoadhesion was noted to all formulations, except to systems composed by 15% (w/w) of Polox. The analyses enabled to understand and predict the performance of formulations and the polymer-Mb interactions, tailoring to the suit systems (Polox/Carb/Mb): 17.5/0.50/0.20 and 20/0.15/0.25.

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PURPOSE: Photodynamic therapy (PDT) with methylene blue (MB) constitutes a potentially useful modality for colorectal cancer treatment. The limitations of the formulations containing MB are problems of administration and the inability to get the closeness contact at the site during the appropriate residence time. Present study aimed to develop and characterize mucoadhesive thermoresponsive system containing MB designed as platform for colorectal cancer therapy. METHODS: Formulations composed of different amounts of poloxamer 407 (Polox), Carbopol 934P (Carb), and MB were developed and characterized as rheological, compressional, mucoadhesive and syringeability properties, toxicity, photodynamic action, in vitro MB release profile, and ex vivo MB intestinal permeation. RESULTS: The different compositions resulted in formulations with distinctive macroscopic characteristics and wide range of gelation temperatures. The compressional flow, mucoadhesive, syringeability, and rheological properties were significantly influenced by temperature and/or composition. The MB release from formulation was governed by anomalous transport. In addition, it was observed that MB permeated the intestinal membrane; the formulation possesses photodynamic activity and low toxicity. CONCLUSIONS: The data obtained from the system composed of 20% Polox, 0.15% Carb, and 0.25% MB indicated a potentially functional role in PDT of the colorectal cancer and suggest it is worthy of clinical evaluation.

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The development of binary polymeric mixtures (polymer blends) containing bioadhesive and thermoresponsive polymers can provide new materials for biomedical applications, with higher contact, increased adhesion, prolonged residence time, protection, and in determined cases, secured absorption of an active agent from the site of application. Mixtures were prepared using a wide range of poloxamer 407 and Carbopol 971P(®) amounts. The rheological (flow and oscillatory), sol-gel transition temperature, mechanical (hardness, compressibility, adhesiveness, cohesiveness and elasticity), softness, and mucoadhesive properties of formulations were investigated. Moreover, the interaction between the different proportions of polymers was also analyzed. Continuous shear and oscillatory rheometry identified the plastic flow with various degrees of thixotropy, besides the viscoelastic behavior of formulations. The determination of gelation temperature displayed values ranged from 27.17 to 41.09°C. It was also found that low carbomer concentrations were enough to provide positive interaction parameter. However, the highest values were obtained for the polymeric blends with higher concentration of poloxamer 407. The mucoadhesion and softness index were greater in preparations containing 20% (w/w) poloxamer 407. The rheological, mechanical and mucoadhesive properties of the polymeric blends can be manipulated by changing the concentrations of the polymers and they suggest the blends are worthy of biomedical applications.

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