A dry powder containing dry particles that contain a tiotropium salt, one or more amino acids, and acid content, and optionally, sodium chloride, and/or one or more additional therapeutic agents, wherein the molar ratio of acid to amino acid is from about 0.0005 to about 5, or 0.002 to about 1. In one aspect, the dry powder containing dry particles is suitable for administration to the respiratory tract. In one aspect, the dry powder containing dry particles is a respirable dry powder contains respirable dry particles that contain a tiotropium salt, one or more amino acids, acid content, sodium chloride, and optionally one or more additional therapeutic agents, wherein the tiotropium salt is about 0.01% to about 0.5%, the leucine is about 5% to about 40%, the sodium chloride is about 50% to about 90%, the optional one or more additional therapeutic agents are up to about 30%, and the molar ratio of acid to amino acid is from about 0.002 to about 1, where all percentages are weight percentages on a dry basis and all the components of the respirable dry particles amount to 100%.
