A method to identify heavy metals in pharmaceuticals was introduced in the United States Pharmacopoeia more than 100 years ago.

Pharmaceutical companies are still using the same method, the USP Heavy Metals Limit Test.

The current colorimetric methodology is intended to control metals, which form a sulfide precipitate, such as lead and copper.

These metals are potential contaminants from water pipes, manufacturing equipment and processes.

Risk factors for metal contamination have changed dramatically, for example with the use of metal catalysts, yet standards for their control have changed little in more than 50 years.

The method is no longer fit for purpose and most heavy metal limits currently in place hold little basis in toxicology.

International Pharmaceutical Excipients Council (IPEC) Americas, state they are unaware of any known metal impurity issues impacting patient safety, although they agree on the need to enhance future testing.

However, harmonisation of pharmacopoeia methods made slow progress in the past.