An effervescent composition comprising a core-shell powder consisting of a fine granular core spray-coated with a liquid mixture containing a water-soluble polymer such as hydroxypropylcellulose or hydroxypropylmethylcellulose, and at least one physiologically active substance, especially an acid-sensitive drugs, and enteric coating film, an effervescing component and an auxiliary effervescing agent which provides for controlled release of the physiologically active substance and in useful for preparing uniform solution or suspension having a refreshing sensation on ingestion.