バクロフェン耐性に対するFLEX modeを用いたボーラス投与（bolus infusion mode）の有用性

Usefulness of Bolus Administration Using the FLEX Mode（Bolus Infusion Mode）for Baclofen Tolerance

Ⅰ．はじめに

　バクロフェン髄腔内投与療法（intrathecal baclofen therapy：ITB療法）は痙縮に対する有効な治療法の1つである⁷⁾．

　その利点は，①スクリーニング検査が可能，②システム抜去またはポンプ停止で元の状態に戻せる可逆性，③全身性の抗痙縮効果，④投薬量の調節性，⑤抗痙縮効果の持続性，⑥投薬方法，カテーテル留置位置，他の抗痙縮治療とのコンビネーションなどの発展性である．

　成人の場合，スクリーニングで0.005%のバクロフェン50μgを髄腔内にボーラス投与し，抗痙縮効果があれば0.05%バクロフェン50μg/dayを均等に投薬する単純連続モード（simple continuous mode：SC）でITB療法を開始するのが一般的である．

　しかし，ITB維持療法中に効果が減弱し，急激な投薬量増量が必要になる症例を経験することがある．一般に，同等の抗痙縮効果を得るために投薬量が1年間で100μg/day以上の増量を認めたものが，バクロフェン耐性と定義されている^5,11)．耐性を示す場合には，バクロフェンのボーラス投与を用いたpulsatile bolus infusionが有効であると報告されている^5,6,12)．

　今回当院でITB療法を行う中でバクロフェン耐性と診断し，その対処としてFLEX mode（bolus infusion mode）を用いてpulsatile bolus infusionを行った4例（Table1）を経験したので，その経過と効果について報告する．

　Intrathecal baclofen（ITB）is used to treat intractable spasticity of various etiologies and can provide better control of spasticity through the adjustment of the dose administered through the pump. However, in patients who develop tolerance to baclofen with the standard simple continuous mode, a sharp increase in dose becomes necessary, and spasticity can become harder to control. We investigated whether switching from the simple continuous mode to the bolus infusion mode was effective in controlling spasticity in patients with baclofen tolerance.

　We reported four patients undergoing ITB therapy at our facility who were considered to have developed baclofen tolerance. We observed the number of bolus infusions and total dose suitable for maintaining spasticity control after switching from the simple continuous mode to the bolus infusion mode. After switching to the bolus infusion mode, the total dose could be reduced in the short term；however, in the long term, the frequency of bolus infusions had to be increased to maintain spasticity control. Two years after changing to bolus infusion six times a day, the total dose was higher than that in the simple continuous mode for two of the four patients, and was the same level in the other two patients.

　Our four cases suggest that bolus infusion is effective in patients with baclofen tolerance during ITB therapy. Therefore, the conditions of bolus infusion should be further investigated.