We
have seen the European Agency for the Evaluation of
Medicines (EMEA) recently include more rigorous
environmental fate testing in European Union (EU)
Environmental Risk Assessment (ERA) guidance to assess
the ultimate fate in water/sediment systems. Yet to date,
there is little data available that covers the fate of
pharmaceuticals in the water/sediment compartment, and
little that assess whether current aerobic and anaerobic
methods are appropriate for pharmaceuticals. In this study,
the biodegradation profiles of 3 Pfizer products were
investigated following the latest ERA guidance and its
recommendation for OECD 308 water/sediment biodegradation
testing. Experiments included 14C-labeled exemestane,
azithromycin, and varenicline representing neutral and
cationic pharmaceuticals with average Koc values of 3704,
49 400, and 10 483 respectively. Specific HPLC/radioactive
monitoring (RAM) methods were used to profile
water and sediment samples for biotransformation products.
Binding to sediment, as “non-extractables”, was considerable
for all three pharmaceuticals, though most notable for
the cationic pharmaceuticals varenicline and azithromycin
ranging from 52% to 94% at study termination, respectively.
In general, for all 3 pharmaceuticals studied, the anaerobic
conditions demonstrated less biotransformation and
mineralization than the aerobic; though their biotransformation
profile (number of metabolites) and amount bound to
sediment were similar. Based on these findings and our
current understanding of anaerobic biodegradation,wewould
recommend a tiered approach to the OECD 308 water/
sediment test: with default testing just for aerobic conditions;
and then if needed, anaerobic testing only for those
compounds potentially amenable to typical anaerobic
processes. We suggest that as a simulation test would be
better suited in later tier testing under EU ERA guidance.
Inherent biodegradation or die-away tests seem better suited
to derive biodegradation rate constants for subsequent
environmental modeling of water and sediment compartments.