Pradeep R. Vavia

Preparation and in vivo evaluation of SMEDDS (self-microemulsifying drug delivery system) containing fenofibrate

The present work was aimed at formulating a SMEDDS (self-microemulsifying drug delivery system) of fenofibrate and evaluating its in vitro and in vivo potential. The solubility of fenofibrate was determined in various vehicles. Pseudoternary phase diagrams were used to evaluate the microemulsification existence area, and the release rate of fenofibrate was investigated using an in vitro dissolution test. SMEDDS formulations were tested for microemulsifying properties, and the resultant microemulsions were evaluated for clarity, precipitation, and particle size distribution. Formulation development and screening was done based on results obtained from phase diagrams and characteristics of resultant microemulsions. The optimized formulation for in vitro dissolution and pharmacodynamic studies was composed of Labrafac CM10 (31.5%), Tween 80 (47.3%), and polyethylene glycol 400 (12.7%). The SMEDDS formulation showed complete release in 15 minutes as compared with the plain drug, which showed a limited dissolution rate. Comparative pharmacodynamic evaluation was investigated in terms of lipid-lowering efficacy, using a Triton-induced hypercholesterolemia model in rats. The SMEDDS formulation significantly reduced serum lipid levels in phases I and II of the Triton test, as compared with plain fenofibrate. The optimized formulation was then subjected to stability studies as per International Conference on Harmonization (ICH) guidelines and was found to be stable over 12 months. Thus, the study confirmed that the SMEDDS formulation can be used as a possible alternative to traditional oral formulations of fenofibrate to improve its bioavailability.

Cyclodextrin-based nanosponges encapsulating camptothecin: Physicochemical characterization, stability and cytotoxicity

Camptothecin (CAM), a plant alkaloid and a potent antitumor agent, has a limited therapeutic utility because of its poor aqueous solubility, lactone ring instability and serious side effects. Cyclodextrin-based nanosponges (NS) are a novel class of cross-linked derivatives of cyclodextrins. They have been used to increase the solubility of poorly soluble actives, to protect the labile groups and control the release. This study aimed at formulating complexes of CAM with three types of beta-cyclodextrin NS obtained with different cross-linking ratio (viz. 1:2, 1:4 and 1:8 on molar basis with the cross-linker) to protect the lactone ring from hydrolysis and to prolong the release kinetics of CAM. Crystalline (F(1:2), F(1:4) and F(1:8)) and paracrystalline NS formulations were prepared. XRPD, DSC and FTIR studies confirmed the interactions of CAM with NS. XRPD showed that the crystallinity of CAM decreased after loading. CAM was loaded as much as 21%, 37% and 13% w/w in F(1:2), F(1:4) and F(1:8), respectively while the paracrystalline NS formulations gave a loading of about 10% w/w or lower. The particle sizes of the loaded NS formulations were between 450 and 600nm with low polydispersity indices. The zeta potentials were sufficiently high (-20 to -25mV) to obtain a stable colloidal nanosuspension. The in vitro studies indicated a slow and prolonged CAM release over a period of 24h. The NS formulations protected the lactone ring of CAM after their incubation in physiological conditions at 37 degrees C for 24h with a 80% w/w of intact lactone ring when compared to only around 20% w/w of plain CAM. The cytotoxicity studies on HT-29 cells showed that the CAM formulations were more cytotoxic than plain CAM after 24h of incubation.

Controlled porosity osmotic pump-based controlled release systems of pseudoephedrine: I. Cellulose acetate as a semipermeable membrane

A controlled porosity osmotic pump-based drug delivery system has been described in this study. Unlike the elementary osmotic pump (EOP) which consists of an osmotic core with the drug surrounded by a semipermeable membrane drilled with a delivery orifice, controlled porosity of the membrane is accomplished by the use of different channeling agents in the coating. The usual dose of pseudoephedrine is 60 mg to be taken three or four times daily. It has a short plasma half life of 5-8 h. Hence, pseudoephedrine was chosen as a model drug with an aim to develop a controlled release system for a period of 12 h. Sodium bicarbonate was used as the osmogent. The effect of different ratios of drug:osmogent on the in-vitro release was studied. Cellulose acetate (CA) was used as the semipermeable membrane. Different channeling agents tried were diethylphthalate (DEP), dibutylphthalate (DBP), dibutylsebacate (DBS) and polyethyleneglycol 400 (PEG 400). The effect of polymer loading on in-vitro drug release was studied. It was found that drug release rate increased with the amount of osmogent due to the increased water uptake, and hence increased driving force for drug release. This could be retarded by the proper choice of channeling agent in order to achieve the desired zero order release profile. Also the lag time seen with tablets coated using diethylphthalate as channeling agent was reduced by using a hydrophilic plasticizer like polyethyleneglycol 400 in combination with diethylphthalate. This system was found to deliver pseudoephedrine at a zero order rate for 12 h. The effect of pH on drug release was also studied. The optimized formulations were subjected to stability studies as per ICH guidelines at different temperature and humidity conditions.

Stability indicating HPTLC method for the simultaneous determination of pseudoephedrine and cetirizine in pharmaceutical formulations

The combination of pseudoephedrine and cetirizine is widely used in the treatment of allergic rhinitis. A rapid, selective and stability indicating high performance thin layer chromatographic method was developed and validated for their simultaneous estimation in pharmaceutical dosage forms. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of ethyl acetate-methanol-ammonia (7:1.5:1, v/v/v). This system was found to give compact spots for both pseudoephedrine (Rf value of 0.69+/-0.01) and cetirizine (Rf value of 0.38+/-0.01). Also the degraded products were well separated from the pure drugs. Spectrodensitometric scanning-integration was performed at a wavelength of 240 nm. The polynomial regression data for the calibration plots showed good linear relationship with r(2)=0.9947 in the concentration range of 10-26 microg for pseudeophedrine and 200-1200 ng for cetirizine with r(2)=0.9973. The method was validated for precision, accuracy, ruggedness and recovery. The minimum detectable amounts were found to be 2 microg and 500 pg for pseudoephedrine and cetirizine, respectively. The limits of quantitation were found to be 6 microg for pseudoephedrine and 800 pg for cetirizine. Both the drugs do not undergo degradation under acidic and basic conditions. The samples degraded with hydrogen peroxide showed additional peaks at Rf values of 0.75 and 0.28 for pseudoephedrine and cetirizine, respectively. This indicates that both the drugs are susceptible to oxidation. Statistical analysis proves that the method is reproducible and selective for the simultaneous estimation of pseudoephedrine and cetirizine. As the method could effectively separate the drugs from their degradation products, it can be employed as a stability indicating one.

Eudragits : Role as crystallization inhibitors in drug-in-adhesive transdermal systems of estradiol

A transdermal steroidal delivery system usually contains a high concentration of drug to obtain high drug fluxes. The present investigation involved the development of drug-in-adhesive transdermal systems of estradiol using synthesized acrylate copolymer (EA) of 2-ethylhexyl acrylate and acrylic acid. The effect of several variables such as varying drug polymer ratios, effect of Eudragit RL PO and Eudragit E PO and effect of drying temperatures on prevention of drug crystallization in the formulation matrix was investigated. The systems free from drug crystals were evaluated and compared with a marketed formulation with respect to its skin permeation profile. The optimized formulation was also subjected to accelerated stability testing. Eudragit RL PO and Eudragit E PO were found to be effective as crystallization inhibitors in the transdermal matrix systems tested. Formulations fabricated with Eudragit E PO gave transparent systems with good film properties and a higher skin permeation profile as compared to that of the marketed system. Higher temperature and humidity conditions facilitated the formation of drug crystals, whereas no crystals were observed in the formulation matrix at 23+/-0.5 degrees C and at 30+/-1 degrees C for the period of 6 months studied.

Nanosponge formulations as oxygen delivery systems

Three types of cyclodextrin nanosponges were synthetized cross-linking α, β or γ cyclodextrin with carbonyldiimidazole as cross-linker. Nanosponges are solid nanoparticles previously used as drug carriers. In this studies cyclodextrin nanosponges were developed as oxygen delivery system. For this purpose the three types of nanosponges suspended in water were saturated with oxygen and in vitro characterized. The nanosponge safety was tested on Vero cells. Their ability to release oxygen in the presence and in the absence of ultrasound (US) was determined over time. Oxygen permeation through a silicone membrane was obtained using a β-cyclodextrin nanosponge/hydrogel combination system. Nanosponge formulations might be potential gas delivery systems showing the ability to store and to release oxygen slowly over time.

Enhanced oral paclitaxel bioavailability after administration of paclitaxel-loaded nanosponges

The aim of this study was to evaluate the pharmacokinetics of paclitaxel-loaded nanosponges (PLN) in rats. The study also evaluates the intrinsic effect of the dosage form on the improvement of paclitaxel oral bioavailability. Paclitaxel-loaded nanosponges were prepared and characterized in terms of size distribution, drug solubilization, and the kinetics of paclitaxel sedimentation. Taxol® and paclitaxel-loaded nanosponges were administered orally to rats. The plasma concentration of paclitaxel was determined using liquid chromatography. The average size of PLN was 350 ± 25 nm. The drug payload of paclitaxel was 500 ± 0.27 mg/g of lyophilized powder. The encapsulation efficiency was 99.1 ± 1.0%, and 1.7 ± 0.2% of paclitaxel was crystallized after 48 h. The relative oral bioavailability of paclitaxel-loaded nanosponges was 256. After oral administration of paclitaxel-loaded PLN, the area under the plasma concentration time curve was significantly increased (∼ 3-fold) in comparison to the control group (p < 0.05). The results indicated that PLN provided a promising new formulation to enhance the oral bioavailability of paclitaxel while avoiding the use of cremophore El: Ethanol in Taxol®.

Once daily sustained release tablets of venlafaxine, a novel antidepressant

Venlafaxine is a unique antidepressant that differs structurally from other currently available antidepressants. Sustained release tablets of venlafaxine to be taken once daily were formulated with venlafaxine hydrochloride equivalent to 75 mg of venlafaxine base. Matrix system based on swellable as well as non-swellable polymers was selected for sustaining the drug release. Different polymers viz. hydroxypropylmethylcellulose (HPMC), cellulose acetate, Eudragit RSPO, ethylcellulose etc. were studied. Combinations of non-swellable polymers with HPMC were also tried in order to get the desired sustained release profile over a period of 16 h. The effect of drug to polymer ratio on in vitro release was studied. The marketed formulation was evaluated for different parameters such as appearance, weight variation, drug content and in vitro drug release. The optimized formulation was subjected to stability studies at different temperature and humidity conditions as per ICH guidelines. These were evaluated for appearance, weight variation, thickness, hardness, friability, drug content and in vitro drug release at selected time intervals. In vivo studies were carried out for the optimized formulation in 12 healthy human volunteers and the pharmacokinetic parameters were compared with the marketed one.

Encapsulation of Acyclovir in new carboxylated cyclodextrin-based nanosponges improves the agent's antiviral efficacy

Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of cyclodextrins that have been proposed as delivery systems for many types of drugs. Various NS derivatives are currently under investigation in order that their properties might be tuned for different applications. In this work, new carboxylated cyclodextrin-based nanosponges (Carb-NS) carrying carboxylic groups within their structure were purposely designed as novel Acyclovir carriers. TEM measurements revealed their spherical shape and size of about 400 nm. The behaviour of Carb-NS, with respect to the incorporation and delivery of Acyclovir, was compared to that of NS, previously investigated as a drug carrier. DSC, XRPD and FTIR analyses were used to investigate the two NS formulations. The results confirm the incorporation of the drug into the NS structure and NS-Acyclovir interactions. The Acyclovir loading into Carb-NS was higher than that obtained using NS, reaching about 70% (w/w). In vitro release studies showed the release kinetics of Acyclovir from Carb-NS to be prolonged in comparison with those observed with NS, with no initial burst effect. The NS uptake into cells was evaluated using fluorescent Carb-NS and revealed the nanoparticle internalisation. Enhanced antiviral activity against a clinical isolate of HSV-1 was obtained using Acyclovir loaded in Carb-NS.

Cyclodextrin-based nanosponges: effective nanocarrier for Tamoxifen delivery

The purpose of the present study was to develop Tamoxifen loaded β-cyclodextrin nanosponges for oral drug delivery. The three types of Tamoxifen loaded β-cyclodextrin nanosponges were synthesized by varying the molar ratios of β-cyclodextrin to carbonyldiimidazole as a crosslinker viz. 1:2, 1:4 and 1:8. The Tamoxifen nanosponge complex (TNC) with particle size of 400–600 nm was obtained by freeze drying method. Differential scanning calorimetry, Fourier transformed infra-red spectroscopy and X-ray powder diffraction studies confirmed the complexation of Tamoxifen with cyclodextrin nanosponge. AUC and Cmax of TNC formulation (1236.4 ± 16.12 µg·mL−1 h, 421.156 ± 0.91 µg/mL) after gastric intubation were 1.44 fold and 1.38 fold higher than plain drug (856.079 ± 15.18 µg·mL−1 h, 298.532 ± 1.15 µg/mL). Cytotoxic studies on MCF-7 cells showed that TNC formulation was more cytotoxic than plain Tamoxifen after 24 and 48 h of incubation.