In this study, symmetric membrane coated tablets were prepared to control delivery of drug in oral osmotic pump system. Effects of various preparation parameters such as concentration of the polymer, concentration of the pore former, thickness of membrane and presence of carbon nanotubes as additives on the permeability and the release characteristics of indomethacin drug was evaluated. The main purpose of this research was to inspect capability of using multi-walled carbon nanotubes (MWCNTs) in drug delivery membranes systems for improving the release rate. The results indicate that addition of virgin MWCNTs in coating solution undesirably decreases the rate of indomethacin release, because MWCNTs tend to agglomerate and make bundles in solution. However, addition of low amounts of functionalized MWCNTs (0.01 wt.%) to cellulose acetate (CA) increased the release rate and improved zero order release pattern of indomethacin. This was attributed to increasing hydrophilicity and changing structure and porosity of the membranes by blending functionalized MWCNTs. The coated membrane on the tablet was broken in higher content of oxidized MWCNTs. Addition of acid oxidized MWCNTs (0.01 wt.% with respect to CA) in coating solution containing 5 wt.% CA and 10 wt.% PEG; and membrane thickness of 500 mu m was adopted as a suitable formulation. (C) 2011 Elsevier B.V. All rights reserved.