The aim of this work was to compare the naproxen availability from hydroxypropyl methylcellulose (HPMC) matrix tablets containing the same dose and a 2-fold weight variation (160 mg of naproxen in tablets weighting 250 and 500 mg) or with the same weight and a 2-fold dose variation (500 mg of weight and 160 or 320 mg of naproxen). The 2-fold weight variation in tablets with the same dose and also the 2-fold dose variation in tablets with the same weight did not affect the naproxen release. In addition, the release rate of two tablets of the same formulation and one tablet with a 2-fold dose and weight variation was not significantly different at the first minutes of the dissolution assay.