Seidlitz powder is a commonly used laxative medication, which contains sodium bicarbonate and tartaric acid that act together to create carbon dioxide gas. However, the term Seidlitz powder may not be well-known to everyone, and some synonyms for this medication could be useful. Some suggested synonyms include effervescent salts, effervescing powders, and fizzy powders. Another option could be to simply use the term "laxative powder," which is more general and can refer to various types of medication used for treating constipation. Ultimately, the most appropriate term may depend on the context in which the medication is being discussed.