Introduction Clopidogrel is a medicine that prevents platelet adhesion and is therefore used to reduce the risk of blood clots. In children’s cardiology, clopidogrel is usually added in combination with aspirin for patients who have had operations and procedures that carry a higher risk of thrombosis.

In children, there are two major studies that assessed the use of clopidogrel to inhibit platelet aggregation and reduce blood clots; PICOLO¹ and CLARINET.² PICOLO showed that a dose of 0.2mg/kg once a day is effective at inhibiting platelet aggregation. CLARINET showed aspirin and clopidogrel had no significant benefit over aspirin monotherapy at preventing blood clots. However, this was in a very specific cohort of patient with complex heart disease. Due to the significant morbidity and mortality associated with blood clots and lack of suitable alternatives, clopidogrel is still used within children’s cardiology for patients who have multiple risk factors for blood clots from platelet adhesion.

The aim of this audit was to establish the nature of prescribing of clopidogrel within our specialist centre compared to the published data.

Method We collected data retrospectively using the pharmacy dispensing system JAC® to identify patients who had received clopidogrel over a two year period from July 2019 to June 2021. Patients were then included if they continued clopidogrel at discharge. Patient characteristics such as weight, indication, dose and administration instructions were gathered from our electronic patient record and made anonymous prior to anaylsis using Microsoft Excel®.

Results We identified 8 patients who had been prescribed clopidogrel over the 2 year period. The median average age at the start of treatment was 5.4 years (range 1.1 to 10.7 years), the median average weight was 21.4kg (range 11.7 to 41.6kg) and the median average dose was 0.71mg/kg (range 0.23 to 1.8mg/kg). The indications included shunts (n=3), devices/stents (n=4) and aspirin allergy (n=1). A review of administration instructions for families at hospital discharge found three inappropriate manipulations. This was due to the use of tablets to provide a small dose that was deemed to carry a risk of inconsistent dosing and difficulty for families to administer.

Conclusion This project has shown that the use of clopidogrel in our centre was variable and in a non-standard fashion. This is demonstrated by the wide range of doses prescribed and the methods used to administer them. This is likely due to the lack of evidence to guide prescribing in unusual circumstances. As a result, we have written guidance based on this review to encourage safer prescribing, particularly to avoid unsafe and unnecessary manipulation of formulations to give small doses. We also now have an unlicensed liquid available for infants who require small doses. For older children, prescribing of fractions of a tablet (e.g. 18.75mg, 37.5mg) is encouraged.

References

1. Li JS, Yow E, Berezny KY, et al. Dosing of clopidogrel for platelet inhibition in infants and young children: primary results of the platelet Inhibition in children on clopidogrel trial. Circulation 2008;117:553-559.

2. Wessel DL, Berger F, Li JS, et al. Clopidogrel in infants with systemic-to-pulmonary-artery shunts. New England Journal of Medicine 2013;368:2377-2384.