The first generation HPMC capsules developed were manufactured by a process similar to gelatin in which a hot solution of HPMC is made and cold stainless steel pins are used to dip into the polymer bath. The polymer film is formed and as the shells dry, they are cut and then removed from the pins. In order to produce HPMC capsules this way, a gelling agent and gelling promotion agent are needed to provide the film formation. Gelling agents such as carrageenan or gellan gum have been used to assist with film formation. HPMC is not self-gelling like gelatin. The added gelling agent combines individual strands of HPMC into longer polymer chains. These large strands are net negative (anionaically) charged which requires the use of a gel promoter like potassium chloride to balance the charge and make even larger chains that have enough size to deposit on the cold stainless steel pins.
While successful in forming films for capsules, these gelling agents and promoters can and do interact with dissolution media causing variability to occur. Sometimes the variability is due to variability by pH and sometimes variability is a reaction to the ionic strength of the dissolution medium or a result of both.
As customers globally tested the first generation HPMC capsules and experienced the variability, it was clear an alternative process was needed in which gelling systems were not used. That was the genesis of Vcaps Plus which was created through a proprietary manufacturing process that eliminated the need of either a gelling agent or gel promoter – only HPMC and water. Vcaps Plus are free from variability related to either pH value or ionic strength of the dissolution media.