droplet size

The objective of the present study was to formulate a solid self micro emulsifying drug delivery system (SMEDDS) for oral administration to improve the solubility and bioavailability of Nimorazole. Solubility was determined in various oils, surfactants and cosurfactants. Of  all the oils accessed for drug solubility, Capmul PG 8 NF showed higher solubility for drug and was better microemulsified using combination of Labrasol and Labrafac CC surfactant. The optimal formulation consists of 30% Capmul PG 8 NF, 50% Labrafac CC,20% Labrasol , was adsorbed on carriers Aerosil200, Microcrystalline cellulose (MCC) and Kaolin .The SMEDDS and solid SMEDDS were characterized for Percent transmittance (%T). Those formulations which showed higher value for %T were evaluated for droplet size, polydispersity index, ζ potential, refractive index and cloud point measurement. Effect of drug loading on droplet size, increasing dilution in different media, thermodynamic stability and in vitro dissolution was performed to observe the performance of the selected formulation. The solid SMEDDS are characterized by globule size analysis, and drug release studies of formulations are compared with plain drug. Adsorption on kaolin produced SMEDDS with the desired globule size and drug release. There was an increase in both the solubility and dissolution rate of drug in S-SMEDDS-K3 as compared to dissolution rate of pure Nimorazole.

Nanoemulsions are only kinetically stable. However, the long term physical stability of nanoemulsions (with no apparent flocculation or coalescence) makes then unique and they are sometimes referred to as ‘Approaching thermodynamic stability. The inherently high colloid stability of nanoemulsions can be well understood from a consideration of their stearic stabilization (when using non-ionic surfactants and /or polymers) and how this is affected by the ratio of the adsorbed layer thickness to droplet radius. Successful ocular drug delivery has largely eluded solution due to, the physiological constraints imposed by the protective mechanisms of the eye that lead to poor absorption of drugs with very small fractions (less than 5%) of the instilled dose penetrating the cornea and reaching the intraocular tissues. Low drug contact time and poor ocular bioavailability due to drainage of solution, tear turnover and its dilution or lacrimation are the problems associated with conventional systems. Novel systems offer manifold advantages over conventional systems as they increase the efficiency of drug delivery by improving the release profile and also reduce drug toxicity. Conventional delivery systems get diluted with tear, washed away through the lacrimal gland and usually require administering at regular time intervals whereas novel emulsions are stable, have improved solubility, required reduced dosing frequency and release drug for prolonged periods of time. The aim of this review focuses on micro and nanoemulsions between 1 and 200 nm with a mean droplet size of about 40nm) for ocular drug delivery.