Improved methods for preparing compositions including a heparinoid, an acute-acting anesthetic, and a buffer are described. These methods result in compositions in which the heparinoid and the acute-acting anesthetic are at least 90% stable for one year. Compositions prepared by these methods and having such improved stability properties are also described, as well as methods for use of these compositions for treating, ameliorating, or preventing lower urinary tract disorders such as interstitial cystitis.
