An in vitro-in vivo investigation of oral bioadhesive controlled release furosemide formulations

Colloidal carriers for extended absorption window of furosemide

Objectives

The aim was to investigate the potential of self-microemulsifying drug delivery systems (SMEDDS) and niosomes as carriers for widening the gastrointestinal absorption window of furosemide (model acidic drug).

Methods

The drug was incorporated in SMEDDS and was encapsulated into niosomes. The intestinal absorption was monitored at two anatomical sites (duodenum and jejuno-ileum). This employed in situ rabbit intestinal perfusion technique.

Key findings

Perfusion of drug solution (control) revealed poor intestinal permeability with per cent fraction absorbed (%Fa) from the duodenum and jejuno-ileum being 1.3 and 0.6 % per cm, respectively. Formulation of furosemide as SMEDDS increased the %Fa from the duodenum and jejuno-ileum to reach 1.7 and 1 % per cm, respectively. Niosomal encapsulation increased the %Fa from duodenum and jejuno-ileum to record 1.9 and 1.2 % per cm, respectively. The increase in the %Fa was also revealed as a reduction in the length required for 95 % absorption of the drug which was reduced from 557.2 to 245.8 cm and to 279.8 cm after delivery as niosomes or SMEDDS, respectively, in case of jejuno-ileum. The same trend was recorded with the duodenum.

Conclusion

The recorded results highlighted the potential for SMEDDS and niosomes for widening the absorption window of acidic drugs after oral administration.

Natural gum as mucoadhesive controlled release carriers: evaluation of cefpodoxime proxetil by D-optimal design technique

The present study deals with the development of mucoadhesive controlled release tablets of Cefpodoxime Proxetil to increase the gastric residence time and thus prolong drug release, reduce dosing frequency and improve oral bioavailability. Tablets were prepared using sodium alginate and karaya gum, a natural polymer, with a synthetic polymer hydroxypropylmethylcellulose (K100LV) and Karaya gum with HPMC K100LV in various ratios to optimize the drug release profile using D-Optimal technique. Pre- and post-compression parameters of tablets prepared with various formulations (S1-S9, C1-C9) were evaluated. The FTIR and DSC studies revealed that no physiochemical interaction between excipients and drug. The formulation S7 showed prolonged drug release, and the mechanism of drug release from the optimized formulation was confirmed using the Korsmeyer-Peppas model to be non-Fickian release transport and n value was found 0.605 indicating both diffusion and erosion mechanism from these natural gums. The optimized formulation showed mucoadhesive strength >35 g. An in vivo study was performed on rabbits using an X-ray imaging technique. The radiological evidence suggests that the tablets adheres (more than 10 hours) to a rabbit's stomach. No significant changes were found in the physical appearance, drug content, mucoadhesive study and in vitro dissolution pattern after storage at 40 °C/75% relative humidity for 3 months.

Evaluation of water uptake and mechanical properties of blended polymer films for preparing gas-generated multiple-unit floating drug delivery systems

Among various strategies of gastroretentive drug delivery systems (DDSs) developed to prolong the gastric residence time and to increase the overall bioavailability, effervescent multiple-unit floating DDSs (muFDDSs) were studied here. These systems consist of drug (losartan)- and effervescent (sodium bicarbonate)-containing pellets coated with a blended polymeric membrane, which was a mixture of gastrointestinal tract (GIT)-soluble and GIT-insoluble polymers. The addition of GIT-soluble polymers, such as hydroxypropyl methylcellulose, polyethylene glycol (PEG) 6000, PEG 600, and Kollicoat® IR, greatly increased the water uptake ability of the GIT-insoluble polymers (Eudragit® NE, RS, and RL; Surelease®; and Kollicoat® SR) and caused them to immediately initiate the effervescent reaction and float, but the hydrated films should also be impermeable to the generated CO(2) to maintain floatation and sufficiently flexible to withstand the pressure of carbon dioxide to avoid rupturing. The study demonstrated that the water uptake ability and mechanical properties could be applied as screening tools during the development of effervescent muFDDSs. The optimized system of SRT(5)P600(5) (i.e., a mixture of 5% Kollicoat® SR and 5% PEG 600) with a 20% coating level began to completely float within 15 min and maintained its buoyancy over a period of 12 h with a sustained-release effect.

Diuretic bioactivity optimization of furosemide in rats

Furosemide is a loop diuretic widely used by patients with congestive heart failure (CHF) to rid excess body water, reducing blood pressure, and mobilizing edemas. However, due to the narrow window of furosemide absorption, occurring only in the proximal gastrointestinal tract, only immediate release oral formulations are clinically available. Comparisons of bolus and continuous administration of furosemide in intravenous settings demonstrate that continuous administration at lower concentrations produced greater diuretic efficiency and reduced subsequent hospitalization rates in patients experiencing severe CHF. We report a systematic investigation of the diuretic bioactivity profiles of phase inversion micronized furosemide and furosemide co-precipitated with Eudragit L100, as well as their blends with stock furosemide, targeted at reducing the rapid spike in diuresis associated with immediate release formulations while maintaining cumulative urine output. Of the formulations tested, an equal parts blend of micronized furosemide and stock furosemide demonstrated optimal diuretic bioactivity profiles in a rat model.

Prolonged intragastric drug delivery mediated by Eudragit® E-carrageenan polyelectrolyte matrix tablets

Interpolyelectrolyte (IPE) complexation between carrageenan (CG) and Eudragit E (EE) was studied in 0.1 M HCl and was used to develop floating matrix tablets aimed to prolong gastric-residence time and sustain delivery of the loaded drug. The optimum EE/CG IPE complexation weight ratio (0.6) was determined in 0.1 M HCl using apparent viscosity measurements. The IPE complex was characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Metronidazole matrix tablets were prepared by direct compression using EE, CG, or hybrid EE/CG with ratio optimal for IPE complexation. Corresponding effervescent tablets were prepared by including Na bicarbonate as an effervescent agent. Tablets were evaluated for in vitro buoyancy and drug release in 0.1 M HCl. Both CG and EE-CG effervescent matrices (1:2 drug to polymer weight ratio, 60 mg Na bicarbonate) achieved fast and prolonged floating with floating lag times less than 30 s and floating duration of more than 10 h. The corresponding EE effervescent matrices showed delayed floating and rapid drug release, and completely dissolved after 3 h of dissolution. CG matrices showed an initial burst drug release (48.3±5.0% at 1 h) followed by slow drug release over 8 h. EE-CG matrices exhibited sustained drug release in almost zero-order manner for 10 h (68.2±6.6%). The dissolution data of these matrices were fitted to different dissolution models. It was found that drug release followed zero-order kinetics and was controlled by the superposition of the diffusion and erosion.

In vivo, in vitro evaluation of linseed mucilage based buccal mucoadhesive microspheres of venlafaxine

The purpose of the present research work was to extract linseed mucilage, use it as a mucoadhesive agent and to develop mucoadhesive microspheres for buccal delivery with an intention to avoid hepatic first-pass metabolism, by enhancing residence time in the buccal cavity. Linseed mucilage was extracted and used to prepare microspheres with varying concentrations of mucilage from formulation F1-F4 (1-2.5%) by spray-drying technique. The microspheres were evaluated for the yield, particle size, incorporation efficiency, swelling property, in vitro mucoadhesion, in vitro drug release, histological study, and stability. Microspheres were characterized by differential scanning colorimetry, scanning electron microscopy, and X-ray diffraction study. Further, the bioavailability study using the New Zealand rabbits was carried out. Formulation F4 showed the maximum mucoadhesion 89.37 ± 1.35%, 92.10 ± 1.37% incorporation efficiency, highest swelling index 0.770 ± 1.23. F4 showed a marked increase in the bioavailability after buccal administration (51.86 ± 3.95) as compared to oral route (39.60 ± 6.16). Also it took less time to reach maximum plasma concentration of 21.38 ± 1.05 ng/ml as compared to oral solution where it required 180 min to reach maximum plasma concentration of 17.98 ± 1.14. It is concluded from the results that linseed mucilage can be used in the production of the mucoadhesive microspheres.

Development and in vitro evaluation of an oral floating matrix tablet formulation of diltiazem hydrochloride

The purpose of this research was to prepare a floating drug delivery system of diltiazem hydrochloride (DTZ). Floating matrix tablets of DTZ were developed to prolong gastric residence time and increase its bioavailability. Rapid gastrointestinal transit could result in incomplete drug release from the drug delivery system above the absorption zone leading to diminished efficacy of the administered dose. The tablets were prepared by direct compression technique, using polymers such as hydroxypropylmethylcellulose (HPMC, Methocel K100M CR), Compritol 888 ATO, alone or in combination and other standard excipients. Sodium bicarbonate was incorporated as a gas-generating agent. The effects of sodium bicarbonate and succinic acid on drug release profile and floating properties were investigated. A 3(2) factorial design was applied to systematically optimize the drug release profile. The amounts of Methocel K100M CR (X1) and Compritol 888 ATO (X2) were selected as independent variables. The time required for 50% (t50) and 85% (t85) drug dissolution were selected as dependent variables. The results of factorial design indicated that a high level of both Methocel K100M CR (X1) and Compritol 888 ATO (X2) favors the preparation of floating controlled release of DTZ tablets. Comparable release profiles between the commercial product and the designed system were obtained. The linear regression analysis and model fitting showed that all these formulations followed Korsmeyer and Peppas model, which had a higher value of correlation coefficient (r). While tablet hardness had little or no effect on the release kinetics and was found to be a determining factor with regards to the buoyancy of the tablets.

Floating granules of ranitidine hydrochloride-gelucire 43/01: formulation optimization using factorial design

The purpose of this research was to develop and optimize a controlled-release multiunit floating system of a highly water soluble drug, ranitidine HCl, using Compritol, Gelucire 50/13, and Gelucire 43/01 as lipid carriers. Ranitidine HCl-lipid granules were prepared by the melt granulation technique and evaluated for in vitro floating and drug release. Ethyl cellulose, methylcellulose, and hydroxypropyl methylcellulose were evaluated as release rate modifiers. A 3(2) full factorial design was used for optimization by taking the amounts of Gelucire 43/01 (X (1)) and ethyl cellulose (X (2)) as independent variables, and the percentage drug released in 1(Q(1)), 5(Q(5)), and 10 (Q(10)) hours as dependent variables. The results revealed that the moderate amount of Gelucire 43/01 and ethyl cellulose provides desired release of ranitidine hydrochloride from a floating system. Batch F4 was considered optimum since it contained less Gelucire and was more similar to the theoretically predicted dissolution profile (f(2) = 62.43). The temperature sensitivity studies for the prepared formulations at 40 degrees C/75% relative humidity for 3 months showed no significant change in in vitro drug release pattern. These studies indicate that the hydrophobic lipid Gelucire 43/01 can be considered an effective carrier for design of a multiunit floating drug delivery system for highly water soluble drugs such as ranitidine HCl.

Compressed collagen sponges as gastroretentive dosage forms: in vitro and in vivo studies

The objective of the present investigations was to develop oblong tablets which expand after contact with gastrointestinal fluids within a few minutes to a length of 4-6 cm and which should remain in the stomach for a prolonged period of time due to their size. The tablets were prepared from riboflavin-containing collagen sponges using a computer controlled single punch tablet machine. The collagen material was compressed to oblong tablets with dimensions of 3.5 mm x 9 mm x 18 mm. In vitro investigations were carried out to characterise drug release. The model drug riboflavin was released from the collagen tablets over 12h. The gastrointestinal retention time of the new dosage form was indirectly estimated by determining the duration of riboflavin excretion after oral intake of the tablet. A crossover in vivo study with 12 healthy male and female subjects was performed. The renal excretion of riboflavin was measured after oral administration of collagen tablets and small sustained release hydrocolloid tablets as reference preparation. The amount of riboflavin excreted into the urine was enhanced after administration of the expanding collagen tablets in comparison with the hydrocolloid tablets. The differences were statistically significant after 5, 6, 8, 9, 10 and 12 h.

Preparation and evaluation of diltiazem hydrochloride-Gelucire 43/01 floating granules prepared by melt granulation

The basic objective of this study was to explore the application of Gelucire 43/01 for the design of multi-unit floating systems of a highly water-soluble drug diltiazem HCl. Diltiazem HCl-Gelucire 43/01 granules were prepared by melt granulation technique. The granules were evaluated for in vitro and in vivo floating ability, surface topography, and in vitro drug release. Aging effect on storage was evaluated using scanning electron microscopy, hot stage polarizing microscopy (HSPM), differential scanning calorimetry (DSC), and in vitro drug release. Granules were retained in stomach at least for 6 hours. Approximately 65% to 80% drug was released over 6 hours with initial fast release from the surface. Surface topography, HSPM, DSC study of the aged samples showed phase transformation of Gelucire. The phase transformation also caused significant increase in drug release. In conclusion, hydrophobic lipid, Gelucire 43/01, can be considered as an effective carrier for design of a multi-unit floating drug delivery system of highly water-soluble drugs such as diltiazem HCl.

Gamma scintigraphic evaluation of the fate of hydroxypropyl methylcellulose capsules in the human gastrointestinal tract

The fate (movement and disintegration) of hard novel hydroxypropyl methylcellulose (HPMC) two-piece capsules in the human gastrointestinal tract was investigated using a gamma scintigraphic imaging method. Two different prolonged-release formulations without an active ingredient were used. The capsules contained different viscosity grades of HPMC powder (HPMC K100 and HPMC K4M). The aim was to determine the main reason why the pharmacokinetic profiles of model drugs change when the diluent was changed to a higher viscosity grade. The results were compared with our previous pharmacokinetic studies with corresponding capsules containing metoclopramide hydrochloride or ibuprofen as a model drug. The first observation was that the HPMC capsules had a tendency to attach to the oesophagus. Therefore, it is recommended that the HPMC capsules as well as gelatine capsules be taken with a sufficient amount of water (150-200 ml) in an upright position and maintaining the upright position for several minutes. The viscosity grade of the HPMC did not affect the transit times of the capsules in the GI tract. The major differences between the two formulations were the complete disintegration times of the capsules and the spreading of the capsules to the large intestine. Most of the HPMC K100-based capsules were completely disintegrated during the 8h study, whereas the HPMC K4M-based capsules still exhibited plug formations in the large intestine. Also the HPMC K100-based capsules spread better to the ascending colon than the HPMC K4M-based capsules. The faster disintegration of the HPMC K100-based capsules explains the differences in the pharmacokinetic profiles of the model drugs between the HPMC K100- and K4M-based capsules in our previous studies. The main absorption site of the drugs from the capsules studied here is probably the large intestine when taken in a fasting state.

Development and in vitro evaluation of novel floating chitosan microcapsules for oral use: comparison with non-floating chitosan microspheres

Floating (F) microcapsules containing melatonin (MT) were prepared by the ionic interaction of chitosan and a negatively charged surfactant, sodium dioctyl sulfosuccinate (DOS). The DOS/chitosan complex formation was confirmed employing infrared spectroscopy, differential scanning calorimetry (DSC), solubility and X-ray diffraction analysis. The characteristics of the F microcapsules generated compared with the conventional non-floating (NF) microspheres manufactured from chitosan and sodium tripolyphosphate (TPP) were also investigated. The effect of various factors (crosslinking time, DOS and chitosan concentrations, as well as drug/polymer ratio) on microcapsule properties were evaluated. The use of DOS solution in coagulation of chitosan produced well-formed microcapsules with round hollow core and 31.2-59.74% incorporation efficiencies. Chitosan concentration and drug/polymer ratio had a remarkable effect on drug entrapment in DOS/chitosan microcapsules. The dissolution profiles of most of microcapsules showed near zero order kinetics in simulated gastric fluid (S.G.F: pH 1.2). Moreover, release of the drug from these microcapsules was greatly retarded with release lasting for several hours (t(50%) (S.G.F.): 1.75-6.7 h, depending on processing factors), compared with NF microspheres where drug release was almost instant. Most of the hollow microcapsules developed tended to float over simulated biofluids for more than 12 h. Swelling studies conducted on various drug-free formulations, clearly indicated that DOS/chitosan microcapsules showed less swelling and no dissolution in S.G.F. for more than 3 days, whereas, TPP/chitosan microspheres were markedly swollen and lost their integrity in S.G.F. within 5 h. Therefore, data obtained suggest that the F hollow microcapsules produced would be an interesting gastroretentive controlled-release delivery system for drugs.

Formulation of an oral dosage form utilizing the properties of cubic liquid crystalline phases of glyceryl monooleate

Glyceryl monooleate is a Food and Drug Administration-approved food additive which has the ability to form various liquid crystalline phases in the presence of various amounts of water. The unique properties of the cubic liquid crystalline phase that result upon the presence of excess body fluids at body temperature were utilized to formulate an oral dosage form containing furosemide as the model drug. The aim was to develop a formula, which has both bioadhesive and sustained release properties of the resultant cubic phase, so that increasing gastric residence time to improve bioavailability of the drug and at the same time obtaining a sustained action. The system was found to be affected by the limited solubility of furosemide in both the carrier system and the pH of surrounding medium. As a consequence, the addition of some solubility modifiers was investigated in order to obtain the desired properties of the expected liquid crystalline system.

A direct-staining method to evaluate the mucoadhesion of polymers from aqueous dispersion

A novel technique to evaluate polymer adhesion to human buccal cells following exposure to aqueous polymer dispersion, both in vitro and in vivo, is described. Adhering polymer has been visualised by staining with 0.1% (w/v) of either Alcian blue (60 min) or Eosin (10 min) solution, uncomplexed dye being removed by 0.25 M sucrose washings. The extent of polymer adhesion was quantified by measuring the relative staining intensity of control and polymer-treated cells by image analysis. In vitro, Carbopol 974P, polycarbophil (Noveon AA-1) and chitosan (CL 113) were found to adhere to human buccal cells from 0.10% (w/w) aqueous dispersions of these polymers. Following in vivo administration as a mouthwash, these polymers persisted upon the human buccal mucosa for at least 1 h.