EFFECT OF ELECTROSTATIC CHARGE, FLOW, DELAY AND MULTIPLE ACTUATIONS ON THE IN-VITRO DELIVERY OF SALBUTAMOL FROM DIFFERENT SMALL-VOLUME SPACERS FOR INFANTS

Background - A study was undertaken to determine the influences of ele ctrostatic charge, flow, delay, and multiple actuations on the in vitr o delivery of salbutamol generated by a pressurised metered dose inhal er (pMDI) from small volume spacers used in infants. Methods - Ten act uations from a salbutamol pMDI were drawn at different flow rates afte r either single or multiple actuations, with or without delay, through either static or reduced static spacers. An ionic detergent was used to reduce the charge of plastic spacers (Babyhaler, Babyspacer, Aeroch amber, Nebuhaler). Electrostatic charge was measured using an electrom eter. A multistage liquid impinger was used to determine the particle size distribution of the output of the pMDI through the spacers. Resul ts - Electrostatic charge on the surface of plastic spacers had the gr eatest influence on delivery, causing a decrease in drug delivery. Red ucing charge by coating the surface with ionic detergent resulted in a n increase of 46.5-71.1% (p<0.001) in small (<6.8 mu m) particle deliv ery from small volume plastic spacers. Lower flow, delay, and multiple actuations resulted in decreased delivery from static spacers. Lower flow resulted in a decrease of 15% in small (<9.6 mu m) particle deliv ery. Delay and multiple actuations resulted in a decrease of 40.7% and 76.0%, respectively, in small (<6.8 mu m) particle delivery. The infl uences of lower flow, delay, and multiple actuations were greatly redu ced or even eliminated by reducing charge. However, multiple actuation s still resulted in a significant decreased delivery (p<0.05). The red uced static Nebuhaler had a higher delivery than all small volume spac ers. Conclusions - Electrostatic charge has a major influence on the d elivery of salbutamol from small volume spacers. Using a metal spacer or ionic detergent coating of plastic spacers resulted in no or reduce d charge and hence in improved delivery. Lower flow, delay, and multip le actuations played a major part only in static spacers.