Key points are not available for this paper at this time.
C. W. Dunnett, M. Gent, Significance Testing to Establish Equivalence between Treatments, with Special Reference to Data in the Form of 2 x 2 Tables, Biometrics, Vol. 33, No. 4 (Dec., 1977), pp. 593-602
Dunnett et al. (Thu,) studied this question.