Magnesium stearate increases salbutamol sulphate dispersion: what is the mechanism?

Tracy Tay, Shyamal Chandra Das, Peter James Stewart

Research output: Contribution to journalArticleResearchpeer-review

31 Citations (Scopus)


The objective was to understand the mechanism of enhancement in salbutamol sulphate (SS) respiratory deposition through addition of magnesium stearate (MgSt). The mixing of MgSt with micronized SS occurred using a Turbula mixer (101 rpm), whilst varying mixing time and MgSt concentration and size. Deposition of SS was determined by a twin-stage impinger. Particle size distributions were obtained using the Malvern Mastersizer 2000. Morphology was examined by scanning electron microscopy and surface energy determined using inverse gas chromatography. Mixing of SS with increasing concentrations of MgSt improved dispersion (FPF of 3.3 using 1 w/w MgSt, 4.5 using 5 w/w MgSt and 7.8 using 10 w/w MgSt compared with 1.4 of pure SS for 20mg doses) when mixed for 0.5h; SS dispersion improved further after 3.5h of mixing. In addition to the action of the MgSt in coating SS particles, a greater understanding of the function of MgSt particles in acting as micro-carriers and in changing the mixture structure through incorporation into agglomerates has been achieved. The mechanistic understanding of improvement in drug deposition using MgSt will allow more directed strategies to be employed in designing powder formulations for inhalation.
Original languageEnglish
Pages (from-to)62 - 69
Number of pages8
JournalInternational Journal of Pharmaceutics
Publication statusPublished - 2010

Cite this