Sigma Healthcare, the retail and pharmacy giant that merged with Chemist Warehouse, expects to continue opening up to 30 new stores in Australia each year as demand for weight-loss medicines and other cheap drugs drives double-digit sales growth.

In its first trading update since Chemist Warehouse completed its reverse takeover of the group in February, Sigma said pre-tax earnings for the combined group rose 36 per cent for the nine months to the end of March.