Design of superdisintegrant- and effervescent agent-less dispersible fast-release melt pellets

A New Challenge for the Old Excipient Calcium Carbonate: To Improve the Dissolution Rate of Poorly Soluble Drugs

Calcium carbonate is an excipient traditionally used in solid dosage forms with several functions such as a diluent, a quick dissolution agent, a buffer and an opacifier. Recently, many other challenges have arisen for calcium carbonate and, among them, the possibility of using it as an excipient for improving the dissolution rate of poorly soluble drugs. As a consequence of their poor solubility in biological fluids, many active ingredients suffer from low and erratic bioavailability when administered by the oral route and thus, many formulation strategies and excipients have been proposed to overcome this problem. Among them, calcium carbonate has been proposed as an excipient for improving dissolution rates. Calcium carbonate has many interesting characteristics, in fact it dissolves quickly in gastric fluid, is inexpensive and is safe. It exists in different polymorphic forms and in porous morphology and recently a porous functionalized calcium carbonate has been proposed as a new excipient. This review is the first overview on the use of calcium carbonate as an excipient for improving drug dissolution rates. The drug loading procedure, the physical characterization of the drug/CaCO₃ samples and their dissolution profiles will be described. Moreover, the possible mechanisms of dissolution improvement, such as the presence of the drug in amorphous or polymorphic forms, in small crystals, and the effects of CaCO₃ dissolution in acidic medium will be discussed. Different polymorphic forms of calcium carbonate and the presence of porosity and functionalization will be analyzed as well and their effects on dissolution rates will be discussed.

Drug release, preclinical and clinical pharmacokinetics relationships of alginate pellets prepared by melt technology

INTRODUCTION

Alginate pellets prepared by the aqueous agglomeration technique experience fast drug dissolution due to the porous pre-formed calcium alginate microstructure.

OBJECTIVE

This study investigated in vitro drug release, preclinical and clinical pharmacokinetics relationships of intestinal-specific calcium acetate-alginate pellets against calcium-free and calcium carbonate-alginate pellets.

METHOD

Alginate pellets were prepared by solvent-free melt pelletization instead of aqueous agglomeration technique using chlorpheniramine maleate as model drug.

RESULTS

A fast in situ calcium acetate dissolution in pellets resulted in rapid pellet breakup, soluble Ca(2+) crosslinking of alginate fragments and drug dissolution retardation at pH 1.2, which were not found in other pellet types. The preclinical drug absorption rate was lower with calcium acetate loaded than calcium-free alginate pellets. In human subjects, however, the extent and the rate of drug absorption were higher from calcium acetate-loaded pellets than calcium-free alginate pellets. The fine, dispersible and weakly gastric mucoadhesive calcium alginate pellets underwent fast human gastrointestinal transit. They released the drug at a greater rate than calcium-free pellets in the intestine, thereby promoting drug bioavailability.

CONCLUSION

Calcium acetate was required as a disintegrant more than as a crosslinking agent clinically to promote pellet fragmentation, fast gastrointestinal transit and drug release in intestinal medium, and intestinal-specific drug bioavailability.