The Hospital Authority said on Wednesday it was working on reducing the amount of medicine distributed to patients to reduce wastage.

It said this applied in particular to long-term medications or those taken only when necessary.

The authority's chief pharmacist William Chui said such measures were needed as around one-fifth of patients did not finish their medication.

"Most of the non-adherence of patients is due to the forgetfulness. The second reason is because they are afraid of the side effect of the medication, and the third reason is because their symptoms improved, so they stop it by themselves," he said.

Under the first phase of its new arrangement from March 24, patients will be dispensed a maximum of 24 weeks drug supply each time. For medications exceeding that limit, patients will have to pick up their prescription in person at another time.

For drugs prescribed when needed, such as painkillers, patients will receive no more than 25 percent of the total amount if the prescription is longer than 28 days.

In the second phase of the arrangement - set to be implemented by the fourth quarter of this year - some 'use only when needed' drugs will be dispensed for up to eight weeks.

The authority predicted that such measures could help reduce medical expenses and allow pharmacists to follow-up on a patient's drug usage.

The authority added that there was room for price adjustments, namely the HK$15 paid for 16 weeks' worth of medicine.

"At present, [the fee] is highly subsidised by the governmen," Chui said.

"Any savings from the medication or any savings from the fees and charges will be converted to the listing of new drugs, and also subsidise serious disease drug treatment," he added.

The authority said it's in discussions with officials regarding fee adjustments. It said it would submit a proposal to the government after completing a review.