The angle of internal flow as an indicator of filling and drug release properties of capsule formulations

Abstract

Abstract The cohesiveness of size fractions of acetylsalicylic acid and lactose alone and in various combinations has been determined by estimation of the rate of decrease in volume as a function of tamping under standard conditions. The cohesiveness was quantified in terms of empirically derived characteristic, the angle of internal flow ϕ. The value of ϕ was found to decrease with the particle size of acetylsalicylic acid, but not lactose, and was found to be dependent on the relative proportion and particle sizes of acetylsalicylic acid and lactose when blends of powder were studied. The value of the time for 50% of the drug content to be released from a hard gelatin capsule in an in-vitro dissolution test, T50, was found to decrease with decreasing values of ϕ for capsules containing acetylsalicylic acid alone. For capsules containing powder blends there was no consistent relationship between the value of T50 and ϕ.