Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: Nomifensine, an antidepressant used for eight years in Britain, was particularly popular in the north west of England. Haemolytic anaemia was recognised as a rare side effect, but in 1984 a cluster of six cases was referred to the North West Regional Transfusion Centre, reflecting an incidence of 0.006%. These were collected within 18 months and showed variable serological features, indicating that antibodies associated with nomifensine treatment are neither rare nor of one particular type. The accumulation of this and similar data contributed to its withdrawal from the British market in January, 1986.
Adult