An improved method for preparing a composition including a heparinoid, a local anesthetic, and a buffer for treatment of a lower urinary tract disease or condition can comprise either: (A) (i) providing a heparinoid in solid form or liquid form； (ii) providing a local anesthetic in solid form or liquid form； (iii) adding a liquid buffer to the heparinoid in solid form or liquid form； (iv) adding the local anesthetic to the mixture of the liquid buffer and the heparinoid； and (v) if necessary, adjusting the pH of the mixture of the liquid buffer, the local anesthetic, and the heparinoid so that a pH is achieved of from about 6.8 to about 8.3 is achieved without precipitation of the local anesthetic； or (B) (i)providing a heparinoid in solid form or liquid form； (ii) providing a local anesthetic in solid form or liquid form； (iii) mixing the heparinoid in solid form or liquid form and the local anesthetic in solid form or liquid form； (iv) adding a liquid buffer to the mixture of the heparinoid and the local anesthetic to form a mixture of liquid buffer, the heparinoid, and the local anesthetic； and (v) if necessary, adjusting the pH of the mixture of the liquid buffer, the local anesthetic, and the heparinoid so that a pH is achieved of from about 7.0 to about 7.8 is achieved without precipitation of the local anesthetic. The invention also encompasses a stable premixed liquid composition that avoids precipitation of the local anesthetic.
