When the Ornaran freighter Sanction was destroyed while delivering goods to Brekka, in exchange for a narcotic drug, Margan contacted the USS Enterprise-D and begged Captain Picard to help them repair their remaining ships. Margan and his people believed that the drug was an antidote for a plague. In reality the plague was no longer fatal and the Brekkians had addicted them to the drug in order to obtain goods from the Ornarans.
Picard refused Margan's request but did not tell him of the ruse, because of the Prime Directive. However without the repairs to their ships, Margan and his people would not receive the drug, and eventually beat the addiction. (TNG: "Symbiosis")