The invention relates to a delayed action preparation which comprises a core comprising a drug and a swelling agent and an outer membrane comprising a biodegradable high molecular weight substance characterized in that the swelling agent is contained in a sufficient amount to cause a explosion of the outer membrane of biodegradable high molecular weight substance at a definite time after administration. This preparation provides for free control over the timing of drug release and is suited for administration not only by the oral route but also by the intramuscular, subcutaneous and other routes.
