Background The potential for clinically significant drug interactions (CSDIs) involving patients on ritonavir and cobicistat is high as a consequence of their powerful pharmacokinetic effect on the cytochrome P450 enzyme system, most notably their inhibitory effect on CYP 3A4.

Purpose An audit was conducted to ensure this patient cohort was not unnecessarily exposed to potential drug toxicities as a consequence of a CSDI.

Material and methods All individuals attending our clinic who were receiving the pharmacokinetic enhancers ritonavir or cobicistat were interviewed to determine a full medication history, including medications prescribed by their GP, over the counter medicines, herbal remedies and recreational drugs.

Results Of the 173 patients who admitted to taking a comedication, 66 were taking a medication or medications which had no significant drug interaction associated with them. 107 patients had at least one medication which had an interaction which could potentially require a dose adjustment, close monitoring or a recommendation that these agents should not be coadministered. Only 27% of these comedications were identified in the normal course of an outpatient visit.

Conclusion As a consequence of the audit, we have highlighted the importance of CSDIs among our patient cohort and medical team. We have implemented several innovative strategies to capture the most accurate medication histories and avoid drug toxicities associated with drug interactions.

References and/or Acknowledgements See poster

No conflict of interest.