In a warning letter published this week the US regulator said inspectors who visited the facility last September discovered corroded production equipment.
They also criticised Vista for failing to examine if metal found in pills made at the site was there as a result of the poor condition of the technology.
The FDA also said Vista had not validated production processes for a vasodilator called isoxsuprine hydrochloride previously made at the facility, several batches of which were shipped to the US between 2014 and 2016.
The agency also raised concerns that Vista’s isoxsuprine hydrochloride tablets “appear to be identical, related, or similar (IRS) to Vasodilan tablets, which are the subject of pending Drug Efficacy Study Implementation (DESI) proceeding 6403.”
US approval for Vasodilan was withdrawn in 2009. The drug is still being reviewed under the US DESI programme, which required the FDA to conduct a retrospective evaluation of the effectiveness of the drugs approved between 1938 and 1962.
The FDA said: “Since the withdrawal of the Vasodilan application, FDA has been made aware of adverse event cases that may be associated with use of isoxsuprine hydrochloride.
“While it is generally FDA’s policy to allow drug products subject to an ongoing DESI proceeding to remain on the market during the pendency of the proceeding, if potential safety issues arise or other violations of the FD&C Act are present, we may take appropriate action.”