How Do I Use Didrex? To ensure that Didrex is completely effective in helping you reach your weight loss goals, you should include an improved diet and exercise regimen. Doing so enables you to achieve permanent weight loss, a healthier life, and will save you money in the long run. Directions For Didrex Usage: Follow these directions for usage of Direx diet pills exactly as they are prescribed to you. Take your dose of Didrex 30 minutes prior to a meal. If your are told by your prescri