You're not entirely wrong. Opium reversed the flows of silver specie that was the lifeblood of the China Trade. Before opium, most of the European trade was Mexican or Peruvian silver for tea, or china, or what have you. After opium, it was those Chinese products, or silver, for opium.

Opium addiction ravaged China (although by the point it really became a public health problem, domestic opium production had exploded). But the wild swings in the price of silver fucked the Qing economy, that had a bimetallic currency between silver taels and copper cash.