Conventional eye drops show relatively low bioavailability due to poor precorneal contact time. In situ hydrogels are of great importance in providing sustained ocular drug delivery. By exhibiting elastic properties they resist ocular drainage of the drug leading to longer contact times. In the present study an in situ gelling thermoreversible mucoadhesive gel was formulated of an antibacterial agent, Moxifloxacin HCl using a combination of poloxamer 407 and poloxamer 188 with different mucoadhesive polymers such as Xanthan gum and Sodium alginate with a view to increase gel strength and bioadhesion force and thereby increased precorneal contact time and bioavailability of the drug. Formulations were evaluated for physical parameters like clarity, pH, spreadability, drug content, gelation temperature, gel strength, bioadhesion force and in vitro drug release study. Formulations were found transparent, uniform in consistency and had good spreadability within a pH range of 6.8 to 7.4. A satisfactory bioadhesion (3298 to 4130 Dyne/cm2) on the sheeps corneal surface and good gel strength (95 to 128 sec) was also observed. As the concentration of mucoadhesive polymers in the gel formulation increased, the rate of drug release decreased. The order of drug release was in order: Xanthan gum > Sodium alginate. It was concluded that a thermoreversible in situ gel of Moxifloxacin HCl can be formulated by combining with mucoadhesive polymers and used effectively as safe and sustained ocular drug delivery. This combination provided greater bioadhesion force and gel strength as compared to the thermoreversible polymers i.e., poloxamer 407 (PF 127) or 188 (PF 68) when used alone.

The objective of this investigation was to study the influence of dissolution enhancers such as polyethylene glycol 400, propylene glycol, polyvinylpyrrolidone K30, sodium lauryl sulfate, and Tween 80 on in vitro dissolution of a model active pharmaceutical material--nimesulide. Preliminary studies were conducted using a physical blend of nimesulide, and the adjuvants and solid dispersions were prepared using solvent evaporation and cogrinding methods. Aqueous solution of adjuvants was first triturated with nimesulide, followed by mixing with lactose and microcrystalline cellulose, and finally water was evaporated under vacuum in a cogrinding method. A 33 factorial design was adopted in a cogrinding method using the concentration of polyethylene glycol 400, propylene glycol, and polyvinylpyrrolidone K30 as independent variables. Tween 80 and sodium lauryl sulfate were added in all the batches. Full and reduced models were evolved for different dependent variables. The reduced models were validated using two checkpoints. Angle of repose < 35 degrees, percentage of drug released in 30 min (Q30) > 40%, 45 min (Q45) > 50%, and 120 min (Q12) > 60% were used as constraints for the selection of an optimized batch. Contour plots are presented for the selected dependent variables. Polyvinylpyrrolidone was found to be more effective in increasing the drug dissolution, compared with polyethylene glycol 400 and propylene glycol. The granule flow was adversely affected when high levels of liquid adjuvants were used in formulations. Wettability study was conducted to measure wetting time for pure drug and the optimized batch. Improved drug dissolution was attributed to improved wetting and the solubilizing effect of adjuvants from the pseudosolid dispersions of nimesulide. Significant improvement in drug dissolution was observed (Q120 = 70%), compared with pure drug powder (Q120 = 15%). In conclusion, dissolution of nimesulide can be modulated using an appropriate blend of pharmaceutical adjuvants.

Floating matrix tablets of domperidone were developed to prolong gastric residence time and thereby increased drug bioavailability. Domperidone was chosen as a model drug because it is poorly absorbed from the lower gastrointestinal tract. The tablets were prepared by wet granulation technique, using polymers such as hydroxypropylmethylcellulose K4M, carbopol 934P, and sodium alginate, either alone or in combination, and other standard excipients. Tablets were evaluated for physical characteristics viz. hardness, % friability, floating capacity, weight variation and content uniformity. Further, tablets were evaluated for in vitro release characteristics for 24 h. In vitro release mechanism was evaluated by linear regression analysis. Floating matrix tablets based on combination of three polymers namely; hydroxypropylmethylcellulose K4M, carbopol 934P and sodium alginate exhibited desired floating and prolonged drug release for 24 h. Carbopol loading showed negative effect on floating properties but were found helpful to control the release rate of drug.

Carbamazepine a dibenzapine derivative with structural resembling to the tricyclic antidepressant, it is used to control some types of seizures in the treatment of epilepsy. It is also used to relieve pain due to trigeminal neuralgia. One of the major problems with this drug is its very low solubility in biological fl uids, which results into poor bioavailability after oral administration. Hence present study was carried out to enhance dissolution properties of carbamazepine. Physical mixtures and solid dispersions of carbamazepine were prepared to enhance its water solubility. Physical mixtures and solid dispersions of carbamazepine were prepared by using polyvinyl pyrrolidone K-30, polyethylene glycol 4000 and polyethylene glycol 6000 as water-soluble carrier at various proportion (1:0.1, 1:0.2, 1:0.4, 1:0.6, 1:0.8, by weight) by employing solvent evaporation method. The drug release profi le was studied according to USP XXIII monograph in 1% sodium lauryl sulphate solution. It was found that the dissolution rate and the dissolution parameters of the drug from the physical mixture as well as solid dispersion were higher than those of the intact drug. The degree of the dissolution rate enhancement depended on the nature and the amount of the carrier, i.e., the higher amount of the carrier used, the higher dissolution rate was obtained except for polyvinyl pyrrolidone K-30 and PEG 4000 solid dispersions. Among carrier studied solid dispersion of Carbamazepine: PVP K-30 at 1:0.2 (drug:carrier ratio) gave highest dissolution. The increase in dissolution rate of the drug may be due to increase wettability, hydrophilic nature of the carrier and also possibility due to reduction in drug crystalinity.

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