The invention relates to delivery systems that allow for the pulsatile release of a substance, such as a drug, in response to a change in pH. More specifically, it relates to drug administration to the GI tract, in particular to site-specific intestinal drug delivery via the oral route. Provided is a pH-controlled pulsatile release system (PPRS) comprising a core surrounded by a coating layer, wherein said core comprises an active substance and wherein said coating layer comprises a pH-sensitive coating material wherein a swellable agent is embedded. Said swellable agent is capable of taking up at least 1.1 times, preferably at least 5 times, more preferably at least 10 times its weight in water. Also provided is a pharmaceutical composition comprising a PPRS, in particular a colon-specific PPRS.
