The WHO on Tuesday halted free drug deliveries to private hospitals and NGOs in quake-devastated Haiti following reports patients were being charged for treatment, a spokeswoman said.
"Only public hospitals are going to continue to receive the drugs for free," WHO spokeswoman Marie-Agnes Heine told AFP. "All others will have to pay."
Heine said the World Health Organization was concerned about reports that patients were now being charged for treatment.
The move, which is initially to be in place for three months to allow for a review, also marks a return to the WHO's practice before the January 12 earthquake.
In changing the rules, Heine said the WHO was moving to a "next phase, whereas the immediate response is over and we're going to a more sustained response that is going to be there for a much longer time."
She stressed the rules would allow the WHO to keep a closer watch over its drug stocks, but Heine also said the organization did not want institutions that have begun charging taking advantage of the programme.
"There were reports about hospitals charging patients for treatment," she said. "I think we have to avoid this kind of misuse of materials and supplies.