Entrapment Efficiency of the Carbomer Interpolymer Type B with Different Drug Molecules in Different Solvents

Nova Southeastern University, Davie, Florida, USA

Objective. Determine the entrapment efficiency of the carbomer interpolymer type B (CITB) with cationic and neutral drugs in different types of solvents. Background. CITB is a hydrophobically-modified poly(acrylic acid) polymer that can entrap cationic and non-ionic drugs via electrostatic complexation and hydrophobic association, respectively. This study evaluated the carbomer’s entrapment efficiency with a cationic model drug (dextromethorphan HBr, DEX, representing the electrostatic interaction) and a non-ionic model drug (acetaminophen, APAP, representing the hydrophobic interaction) in different solvents (water, saline, 40% v/v ethanol, vinegar). Methods. Dextromethorphan and acetaminophen were blended with CITB (1:8 ratio) in 10 mL solvent. The preparations were centrifuged and the drug percentage in the supernatant was determined (UV spectrophotometer). The percentage of the entrapped drug was calculated using a mass balance. The sediments after centrifugation were analyzed (DSC, 25–350°C @ 10°C/min.) to confirm CITB-drug entrapment. Results. The DSC thermograms showed that CITB could entrap cationic and non-ionic drug molecules. On the other hand, the UV spectroscopic analysis showed that higher entrapment was obtained with DEX as compared with APAP in all the examined solvents. 63% DEX entrapment versus 19% APAP entrapment in water, 28% versus 7% in 40% ethanol, 51% versus 12% in saline, and 43% versus 8% in vinegar. Furthermore, the results indicated the higher sensitivity of the DEX-CITB entrapment to the solvent type. Conclusion. The entrapment efficiency of CITB is significantly affected by the ionic nature of the drug molecule to be entrapped and the type of solvent. Grants. NSU Grant 335081.