The health ministry plans to ban some drugs currently available in Europe but have yet to reach Japan as part of its efforts to curb substances that are not technically illegal but have narcotic effects.

The Health, Labor and Welfare Ministry will aim to prevent the "loophole" drugs from entering Japan or circulating in the country by designating them as substances whose importation, manufacture and sale are prohibited under the pharmaceutical affairs law, sources said.

Several European-made substances are expected to be subject to the designation — the first under the pharmaceutical law for a drug currently not in circulation in Japan — which will be formalized after the ministry huddles with an advisory body to the health minister and weighs opinions from the general public, the sources said.

The ministry is also considering similar designations for loophole drugs available in the United States and other countries before they reach Japan, according to the sources.

According to the ministry, 73 types of drugs are banned by the pharmaceutical law, but people have often imported slightly modified versions of such drugs to dodge the regulations.

Loophole drugs, sold in adult entertainment shops and online sources often under the guise of herbs and incense, have been increasingly abused by youths.