Pluronic gels for nasal delivery of Vitamin B12. Part I: preformulation study

Thermoreversible nasal gels of Vitamin B(12) using pluronic PF 127 were aimed to improve absorption and patient compliance. In the present research work, effects of Vitamin B(12) and gel additives, viz. PF concentration, osmolarity, polyethylene glycol (PEG 15000) on thermodynamic properties of phase transitions at gelation (T(1)) and gel melting (T(2)) is reported. Aqueous PF 127 gels prepared by cold method containing pluronic (20-24%, w/w), vitamin, sorbitol, PEG, and benzalkonium chloride. T(1) decreases and T(2) increases with vitamin and PF concentration. Gelation range narrows with sorbitol and PEG. Suppression of T(2) is significantly higher than T(1) with both the additives. The linearity was observed only for semilogarithmic plot of PF concentration and 1/T(2) for sorbitol and PEG, which reveals significant interaction of both at gel melting. Enthalpy of both transitions remains unchanged with vitamin indicating no interaction with polymer. Benzalkonium chloride decreased gelation onset temperature. Thermodynamic properties of PF 127 gels are significantly altered with polymer concentration and water-soluble formulation additives.