Effects of Lubricant Level, Method of Mixing, and Duration of Mixing on a Controlled-Release Matrix Tablet Containing Hydroxypropyl Methylcellulose

Abstract The effects of the lubricant magnesium stearate at different concentrations, mixing shear rates, and mixing times on the tablet properties and drug dissolution from controlled-release matrix tablets containing hydroxypropyl methylcellulose 2208, USP (METHOCEL® K4M Premium) have been studied. Diphenhydramine HCl and hydrochlorothiazide were chosen as the model drugs. Spray-dried hydrous lactose (Fast Flo Lactose-316®) and anhydrous dibasic calcium phosphate (A-TAB®) were chosen as the model excipient/fillers. The impact of magnesium stearate on the mechanical strength of tablets appeared to be dependent on the bonding mechanism of the components of the powder mix. Tablets containing A-TAB, which compacts via a brittle fracture mechanism, were harder and had significantly better friability patterns than those prepared using Fast Flo Lactose-316. The compaction of Fast Flo Lactose-316 appears to be a combination of brittle fracture and plastic deformation. Mixes containing lower levels of lubricant (0.2%) generated tablets that had higher crushing strengths than those with higher lubricant levels (2.0%). Drug release was impacted to the greatest extent by the solubility of the drug and excipient/filler but was only slightly affected by the level of magnesium stearate and duration of mixing.