Apparatus is provided, including an adverse drug reaction (ADR) control server (3) including a processor and a data port. The server is configured to receive from a user (20), via the data port, in a first interaction with the user, a list of one or more current medications, and to send to the user a first medication code responsively to the list. In a second interaction with the user, the server receives the first medication code from the user and an indication of a new medication. The server accesses, by the processor, the list of one or more current medications based on the received first medication code, and generates an adverse drug reaction (ADR) warning based on the list of one or more current medications and the new medication. The server sends the user a new medication code based on the list of one or more current medications and the new medication. Other embodiments are also described.