Clozapine Serum Level Timing Audit: Medium Secure Rowan View

Abstract

Aims

To assess the degree of compliance for clozapine serum level timing post clozapine dose using synnovis (previously viapath) and maudsley 14th edition guidelines in a medium secure hospital.

Methods

Electronic prescribing systems were reviewed on each ward to identify clozapine established patients. Viapaths electronic database was reviewed from 01 May 2021 (18 months) and recorded timings were compared to guidelines in Maudsley, 14th edition and synnovis. 12 hours was used as the guideline post dose in OD (once daily), BD (twice daily)/TDS (three times daily) regimes following the night time or evening dose.

Results

4 different types of clozapine prescribing regimes were identified – OD, BD am/nocte or evening, BD pm/night or evening and TDS. 45 patients in total.

OD 12 - most recent bloods 8/12 patients were >15 hours. Total samples in 18 months >12 hours 63.6% (38/55). Total samples in 18 months >15 hours 56.3% (31/55). In the OD group 26 samples are from 2 patients both of whom have samples taken later than 14 hours.

BD 26 - BD mane evening/nocte - 2/5 most recent samples were >15 hours. Total samples in 18 months >12 hours 51.6% (32/62). Total samples in 18 months >15 hours 12.9%(9/62). Need to consider – evening dose time 18:00 compared to 22:00 adding more time.

BD pm evening/night 5 - 2/5 patients > 15 hours. 4/5 patients not at 13-14 hours. Total samples in 18 months >12 hours 75% (9/12). Total samples in 18 months >15 hours 25% (3/12)

TDS 2 - 0 patient > 15 hours, 1 patient at 14 hours. Total samples at 18 months >12 hours - 41.7% (5/12). Total samples at 18 months >15 hours - 16.7% (2/12).

Conclusion

Higher than expected clozapine serum level timing inaccuracy was demonstrated, markedly in bespoke regimes - OD (56.3%) or BD pm evening/night regimes (25%) compared to traditional regimes (TDS 16.7 %, BD am nocte/evening 12.9%). Contributing factors are a knowledge gap amongst services, Maudsley guidelines don't consider bespoke timings when advising trough levels. Findings suggest bespoke regimes need greater consideration when assessing clozapine serum levels.

Action from this initial audit involves informing teams regarding recent samples which are >15 hours post dose. Service education highlighting safety concerns of potential underestimation of clozapine serum level. Guideline change with support from pharmacy. Re audit in 12 months.