Ten years on, pharma industry still testing for implausible alkyl sulfonate ester contaminants

A decade after concerns about the necessity of testing for alkyl sulfonate esters in drugs were raised¹, risk assessment for this potentially mutagenic contaminant is still required by UK and European drug standard authorities.² Other major regulators, such as the US and Japanese ones, do not have similar requirements for sulfonate-salt drugs.

In 2004, the European Pharmacopoeia of pharmaceutical standards introduced a requirement for sulfonate salt drug substances, stipulating that manufacturers must assess the possibility of alkyl sulfonate ester formation. ‘I was told back then that a French professor insisted that a side-reaction could occur during the synthesis of sulfonate salts using an alcohol solvent to produce alkyl-sulfonate impurities,’ says David Snodin, a UK pharmacotoxicology consultant who first highlighted concerns about the need for this testing.