Carbopol Case Study

Carbopol 940 could yield clear gel with desired rheological property. Carbopol 940 was selected as a gelling agent based on preliminary experiments and previous reports due to its widespread use in pharmaceutical formulations and fast dispersion in water (Sahoo et al., 2014; Sharma and Bedi, 2014; Pillai et al., 2015). Moreover, it is speculated that Carbopol with low concentration can be safe for nasal administration (Khan et al., 2010). Carbopol is known to have mucoadhesive properties. It is necessary to remark that the gelation occur after the neutralization of carbopol 940 with triethanolamine. A small amount of neutralizing agent like sodium hydroxide or triethanolamine is added to carbopol 940, which is a polycarboxylic acid, to
P407 and P188 were screened for formulation of in situ gel in concentration range (15-30%). P188 in the tested concentrations (15-30%) failed to give the suitable gelation temperature where all the recorded temperature values were till 50oC and the viscosity of P188 solution were too low for nasal administration. Result revealed that formulations containing P188 have found to be higher gelation temperature compared to body temperature. So, gelation temperature of P188 in in situ gel was not fulfilling the requirement of in situ gel formulation. The previous findings indicate that gelation started to be observed at 47.3oC with a 35% solution of P188 (Abd El Hady et al., 2003). This result was in line with previous literatures that P 188 alone was unable to yield viscosity desirable for gelation at the physiological temperature (Kolsure and Rajkapoor, 2012;Dhingani et al.,
This could be explained on the basis that poloxamer analogs possess a different PEO: PPO ratio that will lead to a different gelation temperature (Abd El Hady et al., 2003; Ammar et al., 2010). It is known that the PPO unit, which is hydrophobic, decreases the gelation temperature, whereas the PEO unit is hydrophilic and increases the gelation temperature. The molecular weight and percentage of hydrophobic portion are determinant factors for gelling behavior. The gel formation occurs only when concentration is above critical micellar concentration (Prajapati and Goyal,