Esterified cellulose ethers which have i) a combination of aliphatic monovalent acyl groups and groups of the formula - C(O) - R - COOA wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, ii) a weight average molecular weight Mw of from 80,000 Dalton to 350,000 Dalton, iii) a Polydispersity Mw/Mn of from 1.3 to 4.1, and iv) a viscosity of up to 4.0 mPa s, measured as a 2.0 wt% solution of the esterified cellulose ether in 0.43 wt% aqueous NaOH at 20 °C, are useful as enteric polymers for pharmaceutical dosage forms.
