PROBLEM TO BE SOLVED: To provide a synovial proliferation inhibitor for prevention and treatment of a disease caused by synovial proliferation, which gives no serious adverse effect and can be continuously used.SOLUTION: A synovial proliferation inhibitor is characterized in that (E)-8β(17)-rhabdo-12-ene-15,16,17-trial, and in addition, an extract comprising one or more of three diterpene compounds are active ingredients.COPYRIGHT: (C)2014,JPO&INPIT【課題】重篤な副作用がなく連用できる、滑膜増殖に起因する疾患の予防、治療のための滑膜増殖抑制剤を提供する。【解決手段】(E)-8β(17)-ラブド-12-エン-15,16,17-トリアールほか3種類のジテルペン類化合物の1種以上を含む抽出物を有効成分とすることを特徴とする滑膜増殖抑制剤【選択図】 なし