Solubilization of bromhexine hydrochloride in aqueous lecithin dispersions. Physicochemical characterization of interactions between drug and carrier

In aqueous systems bromhexine hydrochloride (Br-HCl) has a poor solubility (4.54 mg/g) and displays no amphiphilic character e.g. self association. Th erefore the drug is molecularly dispersed in water until the solubility pro duct of Br-HCl is exceeded. Solubilization of Br-HCl is linearly increased on addition of lecithin; calculations show that 10 mg Phospholipon((R)) 90G (P 90G) enable solubilization of additional 1.25 mg Br-HCl after the solub ility product of Br-HCl has been exceeded. This means that four to Five pho spholipid molecules are needed for the solubilization of one drug molecule. Ternary systems with P 90G concentrations up to 20% have a lamellar micros tructure. The systems are multilamellar vesicle dispersions as polarisation microscopy, transmission electron microscopy and small-angle X-ray diffrac tometry suggest, Furthermore, Br-HCl solubilization leads to a significant reduction of the intermellar distance d and increases the elastic propertie s of the systems. (PNMR)-P-31 data provide evidence that Br-HCl is solubili zed within the lipophilic part of the phospholipid bilayer.