Filling process-induced tribo-charging of lubricated and non-lubricated gelatine and HPMC capsules

Abstract

Tribo-charging can negatively affect pharmaceutical processes and the quality of pharmaceutical products. This study investigates electrostatic charging during the filling of hard capsules intended to be used in dry powder inhalers (DPIs). Gelatin and HPMC capsules without and with external lubricants (sodium lauryl sulfate, carnauba wax, and magnesium stearate) were subjected to automatic powder filling at two filling speeds and two humidities. Tribo-charging was compared among capsules and correlated with filling parameters using a lactose and 1 % budesonide formulation. Further, we evaluated the aerodynamic performance post-filling to determine the relation of the process-induced tribo-charging on in vitro performance. Our findings indicate that capsules exhibited lower levels of charge before processing. Post-filling, gelatin capsules exhibited lower charge compared to HPMC capsules. External lubricants decreased the charge for both types of capsules. At higher filling humidity (51 % RH), capsules generally exhibited lower charge uptake comparing the 22 % RH condition; higher filling speed tends to reduce charge uptake. However, no clear correlation between the charging of capsules during filling and aerodynamic performance was observed. Processing seems to be more affected by the capsule surface properties (roughness and presence of surfactant), while the inhalation performance appears to be affected by the interplay of capsule material and process parameters (filling speed and humidity).

Keywords: Capsule filling; Inhalation; Processing; Static charge; Tribo-charging.