Each one of four very slightly water-soluble to practically water-insoluble, non-steroidal anti-inflammatory, antipyretic and analgesic drugs, such as indomethacin(I), aspirin(II), ibuprofen(III) and flurbiprofen(IV) were dissolved in a N-hexadecyl-N, N, N-trimethylammonium bromide (CTAB) micellar medium and the resulting solutions were titrated with a carbonate-free 2.5 mmol/L NaOH solution. The end point determined potentiometrically by the convetional manner, using the second derivative graph, while the routine analytical applications were carried out either by an automatic titration assembly or by visual titration using the selected acid-base indicator. Results for(I–IV) agreed well with those obtained by the method of the USP XXII and a statistical analysis by means of Student's t-test, as well as by the variance ratio F-test proved that between the proposed method and the official one no significant difference was observed. The method described in the present paper, is simple, precise, inexpensive and it could successfully replace the established non-aqueous techniques.