A year into implementation of their new Good Manufacturing Practice (GMP) guidelines, Chinese authorities have begun an investigation into safety problems of “essential medicines” after a test sample of children’s medication contained twice the allowable amount of mercury.

Today there are more than 4,700 drug manufacturers in China. Of these, nearly 3,000 produce “essential medicines” and will be subject to the investigation by the Chinese FDA (SFDA), which will also look at traditional Chinese remedies. Though the probe is targeted at drugs sold in China, it could turn up manufacturing problems for companies that also import medicines to the U.S. and other countries.

“The two-month examination will look closely at how drugs are produced and where their raw materials are sourced,” the China Daily reported. A report on the findings is expected in June.

Safety problems with Chinese-made drugs that have come into the U.S. have been in the headlines ever since contaminated batches of heparin led to illness and the death of more than 100 American patients in 2007-2008. Last month, a warning letter from the FDA called out an API supplier for falsifying inspection documents and destroying records.

But the new investigation suggests that there are huge domestic failures in China’s drug supply, too. According to the Daily, severe adverse event reports to Chinese were up 16 percent in 2010 from the year before. The new GMP quality measures are designed to bring Chinese manufacturers in line with international standards, and include stricter sterilization requirements, risk management procedures, sanctions and required reporting, audits and adverse event reporting, according to a Gold Sheet story.

But Chinese sites have a 5-year grace period to comply with the 2010 GMP updates, and how the SFDA will staff or enforce the tightened rules is unclear. Regulators in China and abroad must be vigilant in ensuring the process stays on track, and that already-established firewalls keep unsafe and substandard medicines out of both the domestic and international supply chain.

For more on imported drug manufacturing safety, follow SafeRxWatch on Twitter or visit the Pew Prescription Project.

–Kate Petersen, PostScript blogger