One of the principal alkaloids of opium, morphine is a narcotic drug used in medicine for its analgesic effects. Morphine is extracted from the dried milky juice of the unripe seed capsule of the opium poppy. It was first isolated by the German chemist F. W. A. Serturner in the early 1800s. Morphine is extremely effective in relieving severe pain, such as that encountered in connection with gallstones and terminal cancer and in cases where other analgesics fail. It is also used for its calming or sedating effects. Morphine has a euphoric effect on patients, as well as side effects that may be manifested in either the respiratory, circulatory, or gastrointestinal systems. In addition, morphine has an emetic effect (induces vomiting) and is a general depressant. The most serious consequence of morphine use is addiction. Morphine can be converted into a diacetyl derivative called heroin, which can be even more addicting than morphine. Synthetic compounds, such as meperidine (Demerol) and methadone, have largely replaced morphine in medical use.