A Japanese pharmaceutical industry group says shipments of about 20 percent of prescription drugs were limited or halted in October, while pharmacies and medical institutions continue to be running short of drug supplies.

The Federation of Pharmaceutical Manufacturers' Association of Japan made the finding in a survey.

The federation says that out of more than 16,000 items subject to the survey, 3,103 items, or 18.5 percent, were under shipment adjustments or suspensions as of the end of October. Shipments were limited for 10.7 percent of the products, while 7.8 percent were halted.

Of all the items, 1,954 items, or 63 percent, were generic drugs, including antitussives, antipyretics, analgesics, and expectorant medicines.

The percentage of prescription drugs with limited or halted shipments rose to 26.6 percent in February. Though the figure is gradually on the decline, it still stands close to 20 percent.

Supplies of many prescription drugs have been disrupted for more than three years due to problematic production processes involving generic drug makers and the rising demand resulting from the spread of infectious diseases.

Japan's Health, Labor and Welfare Ministry said many generic drug makers produce a large number of items, but only small portions for individual items, making it difficult for them to catch up with a surge in demand.

Ministry officials said they will urge drug makers to ship their inventories and increase production in anticipation of growing demand as winter approaches and colds and other infectious diseases spread.

The officials also said they intend to make efforts to solve structural problems involving generic drug makers, such as their inefficient production systems.