cocaine in the very interests of sobriety
Far from your scenario of relapsing, the Bing is medicinal support for assertively sharing his need for aloneness with Green, so that issues of early sobriety can get resolved before standing in the way of spiritual growth—Lenz will use cocaine in the very interests of sobriety and growth itself.
Context
The relapse-denial engine at its most baroque: Lenz reasons that the cocaine is not a relapse but medicinal support for the work of recovery — a chemical aid to sharing his feelings and resolving early-sobriety issues — so that using becomes, in his own accounting, an instrument of spiritual growth. The Program's entire vocabulary (early sobriety, resolving issues, spiritual growth) is conscripted to license the exact behavior it exists to end. The addict does not evade the doctrine; he wears it as cover.