The present invention relates to the stabilization of such derivatives in solid dosage forms containing certain benzothia (dia) zepine derivatives. In the solid preparation containing (A) the benzothia (dia) zepine derivative and (B) a specific plasticizer, the present invention isolates the component (A) and the component (B), or When the component A) and the component (B) are not separated, the content of the component (B) is 0.9% by weight or less based on the total weight of the solid formulation, or the solid formulation is at least 1 It is set as the form provided with at least 1 coating layer or capsule layer which surrounds at least one part of said core and said core, said (A) ingredient is blended in said core, and said ( B) component is mix blended and the content of the said (B) component in the said coating layer or a capsule layer shall be 45 weight% or less on the basis of the total weight of the said coating layer or a capsule layer.本発明は、ある種のベンゾチア（ジア）ゼピン誘導体を含む固形製剤中の当該誘導体の安定化に関する。本発明は、（Ａ）前記ベンゾチア（ジア）ゼピン誘導体、並びに、（Ｂ）特定の可塑剤を含む固形製剤において、前記（Ａ）成分及び前記（Ｂ）成分を隔離するか、或いは、前記（Ａ）成分及び前記（Ｂ）成分を隔離しない場合は、前記（Ｂ）成分の含量を固形製剤の総重量を基準として０．９重量％以下とするか、又は、前記固形製剤を、少なくとも１つのコア、及び、前記コアの少なくとも一部を包囲する少なくとも１つの被覆層又はカプセル層を備える形態とし、前記コア中に前記（Ａ）成分を配合し、前記被覆層又はカプセル層中に前記（Ｂ）成分を配合し、前記被覆層又はカプセル層中の前記（Ｂ）成分の含量を、前記被覆層又はカプセル層の総重量を基準として４５重量％以下とする。
