V. Satyanarayana

In vitro drug release studies on guar gum-based colon targeted oral drug delivery systems of 5-fluorouracil.

Intravenous administration of 5-fluorouracil for colon cancer therapy produces severe systemic side-effects due to its cytotoxic effect on normal cells. The broad objective of the present study was to develop novel tablet formulations for site-specific delivery of 5-fluorouracil to the colon without the drug being released in the stomach or small intestine using guar gum as a carrier. Fast-disintegrating 5-fluorouracil core tablets were compression coated with 60% (FHV-60), 70% (FHV-70) and 80% (FHV-80) of guar gum, and were subjected to in vitro drug release studies. The amount of 5-fluorouracil released from the compression-coated tablets in the dissolution medium at different time intervals was estimated by a HPLC method. Guar gum compression-coated tablets released only 2.5-4% of the 5-fluorouracil in simulated GI fluids. When the dissolution study was continued in simulated colonic fluids (4% w/v rat caecal content medium) the compression-coated FHV-60, FHV-70 and FHV-80 tablets released another 70, 55 and 41% of the 5-fluorouracil respectively. The results of the study show that compression-coated tablets containing 80% (FHV-80) of guar gum are most likely to provide targeting of 5-fluorouracil for local action in the colon, since they released only 2.38% of the drug in the physiological environment of the stomach and small intestine. The FHV-80 formulation showed no change either in physical appearance, drug content or dissolution pattern after storage at 40 degrees C/RH 75% for 6 months. The differential scanning calorimetric study showed that 5-fluorouracil did not interact with the formulation excipients used in the study.

Three-layer guar gum matrix tablet formulations for oral controlled delivery of highly soluble trimetazidine dihydrochloride

The present study is carried out to design oral controlled drug delivery systems for highly water-soluble drugs using guar gum as a carrier in the form of three-layer matrix tablets. Trimetazidine dihydrochloride was chosen as a model drug because of its high water solubility. Matrix tablet granules containing 30% (M1), 40% (M2) or 50% (M3) of guar gum were prepared by the wet granulation technique using starch paste as a binder. Three-layer matrix tablets of trimetazidine dihydrochloride were prepared by compressing on either side of guar gum matrix tablet granules of trimetazidine dihydrochloride M1, M2 or M3 with 200 mg of guar gum granules containing either 65% of guar gum (T1M1, T1M2 or T1M3), 75% of guar gum (T2M1, T2M2 or T2M3) or 85% of guar gum (T3M1, T3M2 or T3M3) as release retardant layers. The three-layer matrix tablets were evaluated for hardness, thickness, drug content uniformity, and were subjected to in vitro drug release studies. The amount of trimetazidine dihydrochloride released from the matrix and three-layer matrix tablets at different time intervals was estimated using a HPLC method. The three-layer guar gum matrix tablet (T3M3) provided the required release rate on par with the theoretical release rate for guar gum formulations meant for twice daily administration. The three-layer guar gum matrix tablet (T3M3) showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40 degrees C/RH 75% for 6 months. The DSC study did not show any possibility of interaction between trimetazidine dihydrochloride and guar gum/other formulation excipients used in the study. The results indicated that guar gum, in the form of three-layer matrix tablets, is a potential carrier in the design of oral controlled drug delivery systems for highly water-soluble drugs such as trimetazidine dihydrochloride.

A three-layer guar gum matrix tablet for oral controlled delivery of highly soluble metoprolol tartrate.

The objective of the study is to design oral controlled drug delivery systems for highly water-soluble drugs using guar gum as a carrier in the form of a three-layer matrix tablet. Metoprolol tartrate was chosen as a model drug because of its high water solubility. Matrix tablets containing either 30 (M1), 40 (M2) or 50% (M3) of guar gum were prepared by wet granulation technique using starch paste as a binder. Three-layer matrix tablets of metoprolol tartrate were prepared by compressing on both sides of guar gum matrix tablet granules of metoprolol tartrate M1, M2 or M3 with either 50 (TL1M1, TL1M2 or TL1M3) or 75 mg (TL2M1, TL2M2 or TL2M3) of guar gum granules as release retardant layers. Both the matrix and three-layer matrix tablets were evaluated for hardness, thickness, drug content uniformity, and subjected to in vitro drug release studies. The amount of metoprolol tartrate released from the matrix and three-layer matrix tablets at different time intervals was estimated by using a HPLC method. Matrix tablets of metoprolol tartrate were unable to provide the required drug release rate. However, the three-layer guar gum matrix tablets (TL2M3) provided the required release rate on par with the theoretical release rate for metoprolol tartrate formulations meant for twice daily administration. The three-layer guar gum matrix tablet (TL2M3) showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40 degrees C/75% RH for 6 months. The FT-IR study did not show any possibility of metoprolol tartrate/guar gum interaction with the formulation excipients used in the study. The results indicated that guar gum, in the form of three-layer matrix tablets, is a potential carrier in the design of oral controlled drug delivery systems for highly water-soluble drugs such as metoprolol tartrate.

Development of colon targeted drug delivery systems for mebendazole.

The objective of the present study is to develop colon targeted drug delivery systems for mebendazole using guar gum as a carrier. Matrix tablets containing various proportions of guar gum were prepared by wet granulation technique using starch paste as a binder. The tablets were evaluated for drug content uniformity, and were subjected to in vitro drug release studies. The amount of mebendazole released from the matrix tablets at different time intervals was estimated by a high-performance liquid chromatography method. Guar gum matrix tablets released 8-15% of the mebendazole in the physiological environment of stomach and small intestine depending on the proportion of guar gum used in the formulation. When the dissolution study was continued in simulated colonic fluids the matrix tablets containing 20% of guar gum released another 83% of mebendazole after degradation into 2-3 pieces. The matrix tablets containing 30% of guar gum also released about 50% of mebendazole in simulated colonic fluids indicating the susceptibility of the guar gum formulations to the rat caecal contents. The results of the study show that matrix tablets containing either 20% or 30% of guar gum are most likely to provide targeting of mebendazole for local action in the colon. The mebendazole matrix tablets containing either 20% or 30% of guar gum showed no change either in physical appearance, drug content or dissolution pattern after storage at 45 degrees C/75% relative humidity for 3 months. Differential scanning calorimetry indicated no possibility of interaction between mebendazole and guar gum.

In vivo pharmacokinetics in human volunteers: oral administered guar gum-based colon-targeted 5-fluorouracil tablets

The objective of the present study is to compare the guar gum-based colon-targeted tablets of 5-fluorouracil against an immediate release tablet by in vitro dissolution and in vivo pharmacokinetic studies in human volunteers. Twelve healthy volunteers participated in the study. 5-Fluorouracil was administered at a dose of 50 mg both in immediate release tablet and colon-targeted tablet. On oral administration of colon-targeted tablets, 5-fluorouracil started appearing in the plasma at 6 h, and reached the peak concentration (C(max) of 216+/-15 ng/ml) at 7.6+/-0.1 h (T(max)), whereas the immediate release tablets produced peak plasma concentration (C(max) of 278+/-21 ng/ml) at 0.6+/-0.01 h (T(max)). The AUC(0- infinity ) for 5-fluorouracil from colon-targeted tablet and immediate release tablet were found to be 617+/-39 and 205+/-21 ng/ml/h, respectively. Colon-targeted tablets showed delayed t(max), delayed absorption time (t(a)), decreased C(max) and decreased absorption rate constant when compared to the immediate release tablets. The results of the study indicated that the guar gum-based colon-targeted formulation did not release the drug in stomach and small intestine, but delivered it to the colon resulting in a slow absorption of the drug and making it available for local action in colon.

Influence of limonene on the bioavailability of nicardipine hydrochloride from membrane-moderated transdermal therapeutic systems in human volunteers.

The aim of the present study was to develop a membrane-moderated transdermal therapeutic system (TTS) of nicardipine hydrochloride using 2%w/w hydroxy propyl cellulose (HPC) gel as a reservoir system containing 4%w/w of limonene as a penetration enhancer. The permeability flux of nicardipine hydrochloride through ethylene vinyl acetate (EVA) copolymer membrane was found to increase with an increase in vinyl acetate (VA) content in the copolymer. The effect of various pressure-sensitive adhesives (MA-31, MA-38 or TACKWHITE A 4MED) on the permeability of nicardipine hydrochloride through EVA membrane 2825 (28% w/w VA) or membrane/skin composite was also studied. The results showed that nicardipine hydrochloride permeability through EVA 2825 membrane coated with TACKWHITE 4A MED/skin composite was higher than that coated with MA-31or MA-38. Thus a new TTS for nicardipine hydrochloride was formulated using EVA 2825 membrane coated with a pressure-sensitive adhesive TACKWHITE 4A MED and 2%w/w HPC gel as reservoir containing 4%w/w of limonene as a penetration enhancer. The bioavailability studies in healthy human volunteers indicated that the TTS of nicardipine hydrochloride, designed in the present study, provided steady state plasma concentration of the drug with minimal fluctuations for 20 h with improved bioavailability in comparison with the immediate release capsule dosage form.

Studies on the development of colon-targeted delivery systems for celecoxib in the prevention of colorectal cancer.

The nonsteroidal anti-inflammatory drugs (NSAIDs) are found to be potential chemopreventive agents of colorectal cancer. Celecoxib, an NSAID with selective cyclooxygenase-2 inhibition, was proved to be effective for the prevention of colon cancer in patients with familial adenomatous polyposis (FAP) and sporadic polyps. In the light of this information, the present study was carried out to develop oral colon-targeting drug delivery systems for celecoxib using guar gum as a carrier. Matrix tablets containing various proportions of guar gum were prepared by wet granulation technique using starch paste as a binder. The tablets were evaluated for hardness, drug content and were subjected to in vitro drug release studies. The amount of celecoxib released from the matrix tablets at different time intervals was estimated by a HPLC method. Guar gum matrix tablets released only 2-4% of celecoxib in the physiological environment of stomach and small intestine depending on the proportion of guar gum used in the formulation. When the dissolution study was continued in simulated colonic fluids (rat caecal content medium), the matrix tablets containing 20% of guar gum released another 37% of celecoxib after degradation by the colonic bacterial action. The matrix tablets containing 30% of guar gum released about 24% of celecoxib in simulated colonic fluids indicating the susceptibility of the guar gum formulations to the rat caecal contents. The results of the study show that the matrix tablets containing either 20 or 30% of guar gum are most likely to target celecoxib for local action in the colon. The guar gum matrix tablets of celecoxib showed no change either in physical appearance, drug content or in dissolution pattern after storage at 40°C/RH 75% for 6 months. Differential scanning calorimetry (DSC) studies indicated no possibility of interaction between celecoxib and guar gum/other formulation excipients.

Penetration Enhancing Effect of Menthol on the Percutaneous Flux of Nicardipine Hydrochloride Through Excised Rat Epidermis from Hydroxypropyl Cellulose Gels

The aim of the present investigation is to study the penetration enhancing effect of menthol on the percutaneous flux of nicardipine hydrochloride through the excised rat epidermis from 2% w/w hydroxypropyl cellulose (HPC) gel system. The HPC gel formulations containing nicardipine hydrochloride and selected concentrations of menthol (0–12% w/w) were prepared, and evaluated for in vitro permeation of the drug through excised rat abdominal epidermis. The percutaneous flux of nicardipine hydrochloride across rat epidermis was enhanced markedly by the addition of menthol to the HPC gels. A maximum flux of nicardipine hydrochloride (227.70±1.30 μ_rm;g cm−2 hr−1) was observed with an enhancement ratio of 7.12 when menthol was incorporated at a concentration of 8% w/w in a reservoir HPC system. The differential scanning calorimetry and Fourier transform-infrared spectroscopy data indicated that menthol increased the percutaneous flux of nicardipine hydrochloride through the rat skin by partial extraction of lipids in the stratum corneum. The results suggest that menthol may be useful for increasing the skin permeability of nicardipine hydrochloride from transdermal therapeutic system containing HPC gel as a reservoir.

Bioavailability studies on guar gum-based three-layer matrix tablets of trimetazidine dihydrochloride in human volunteers

Guar gum-based three-layer matrix tablets of a highly water-soluble drug, trimetazidine dihydrochloride, were evaluated for their in vivo release in healthy volunteers in comparison with commercially available conventional immediate release tablets. Six healthy volunteers participated in the study and a two-way crossover design was followed. The plasma concentration of trimetazidine dihydrochloride was estimated by reverse-phase HPLC. The pharmacokinetic parameters were calculated from the plasma concentration of trimetazidine dihydrochloride versus time data. The delayed T(max), decreased C(max) and K(a), unaltered bioavailability, and prolonged t(1/2) and MRT indicated a slow and prolonged release of trimetazidine dihydrochloride from guar gum three-layer matrix tablets in comparison with the immediate release tablet dosage form. The guar gum three-layer matrix tablets of trimetazidine dihydrochloride may be useful in providing constant drug delivery with minimum fluctuations.

Influence of menthol and pressure-sensitive adhesives on the in vivo performance of membrane-moderated transdermal therapeutic system of nicardipine hydrochloride in human volunteers.

A membrane-moderated transdermal therapeutic system of nicardipine hydrochloride was developed using 2% w/w hydroxypropylcellulose (HPC) gel as a reservoir system containing 5% w/w of menthol as a penetration enhancer. The permeability flux of nicardipine hydrochloride through the ethylene vinyl acetate (EVA) copolymer membrane was found to increase with an increase in vinyl acetate content in the copolymer. The effect of various pressure-sensitive adhesives (MA-31, MA-38 or TACKWHITE A 4MED on the permeability of nicardipine hydrochloride through EVA 2825 membrane (28% w/w vinyl acetate) or EVA 2825 membrane/skin composite was also studied. The results showed that nicardipine hydrochloride permeability through EVA 2825 membrane coated with TACKWHITE A 4MED/skin composite was higher than that coated with MA-31 or MA-38. Thus, a new transdermal therapeutic system for nicardipine hydrochloride was formulated using EVA 2825 membrane coated with a pressure-sensitive adhesive TACKWHITE A 4MED, and 2% w/w HPC gel as reservoir containing 5% w/w of menthol as a penetration enhancer. In vivo studies in healthy human volunteers indicated that the TTS of nicardipine hydrochloride, designed in the present study, provided steady-state plasma concentration of the drug with minimal fluctuations for 26h with improved bioavailability in comparison with the immediate release capsule dosage form.