The hypothesis that flupenthixol decanoate may serve as an alter-native to prophylactically administered lithium in recurrent manicdepressive illness, bipolar and unipolar type, was tested in two groups of patients. In Group I the patients were allocated randomly to maintenance treatment with either lithium or flupenthixol decanoate. The patients in Group II had previously been given lithium and were switched to flupenthixol decanoate because of unsatisfactory prophylactic effect of lithium, doubtful tablet compliance, troublesome side effects, or fear of later harmful effects. The flupenthixol decanoate dosage was 20 mg every 2–3 weeks. The study was not blind.
In Group I neither lithium treatment (14 patients) nor treatment with flupenthixol decanoate (19 patients) led to a significant fall of mean episode frequency or mean per cent time ill. The reasons for this lack of response are not clear, but prognostically negative selection of the patients presumably took place before and possibly also during the hospitalization. Since absent effects cannot be compared, this part of the trial remains inconclusive.
In Group II (93 patients) treatment with flupenthixol decanoate was associated with significant falls of the frequency of manic episodes and per cent time ill in mania and with significant rises of the frequency of depressive episodes and per cent time ill in depression. Increase of depressive morbidity was seen only in patients who had been given lithium during the pre-trial period and was presumably a result of the discontinuation of lithium.
It is not known whether flupenthixol decanoate is of value in the prophylactic treatment of recurrent manic-depressive illness, but the drug may be worth trying in patients whose disease is dominated more by manic than by depressive recurrences and who do not respond to lithium or do not tolerate it or do not take it.