How to switch a patient from ticagrelor (90 mg twice daily) to clopidogrel after developing an acute cerebellar infarct?

Switching from Ticagrelor to Clopidogrel in a Patient with Acute Cerebellar Infarct

For a patient on ticagrelor 90 mg twice daily who has developed an acute cerebellar infarct, the recommended approach is to administer a loading dose of 300 mg clopidogrel followed by 75 mg daily maintenance dose, while discontinuing ticagrelor immediately. 1

Rationale for Switching

• Ticagrelor increases the risk of intracranial hemorrhage compared to clopidogrel and should be avoided in patients with a history of intracranial hemorrhage or recent stroke 2
• For patients who have experienced a cerebrovascular event while on ticagrelor, switching to clopidogrel is appropriate to reduce the risk of hemorrhagic transformation 2
• Clopidogrel (75 mg daily) is recommended for patients with stroke who cannot receive ticagrelor, including those with prior intracranial bleeding 2

Switching Protocol

1. Discontinue ticagrelor immediately 2

2. Administer clopidogrel loading dose:

   • Give 300 mg oral loading dose of clopidogrel 1
   • This loading dose is necessary to achieve faster platelet inhibition, as initiating clopidogrel without a loading dose will delay establishment of an antiplatelet effect by several days 1

3. Maintenance therapy:

   • Continue with clopidogrel 75 mg once daily 1
   • No overlap period is required between ticagrelor and clopidogrel 2

Special Considerations

• Timing of switch: Implement the switch immediately after confirming the cerebellar infarct diagnosis and ruling out hemorrhagic transformation on neuroimaging 3
• Duration of therapy: Continue clopidogrel for at least 12 months in patients with acute coronary syndrome 2
• Aspirin co-administration: If the patient was on dual antiplatelet therapy:
  • Continue aspirin at a dose of 75-100 mg daily 2
  • Consider a proton pump inhibitor in combination with dual antiplatelet therapy to minimize bleeding risk 2

Monitoring After Switch

• Monitor for signs of recurrent ischemic events, particularly in the first week after switching, as this is when most recurrent events occur 4, 5
• Assess for any bleeding complications, especially during the first few days after the loading dose 4
• For patients who are CYP2C19 poor metabolizers (approximately 2% of White, 4% of Black, and 14% of Asian patients), clopidogrel may have reduced efficacy and alternative antiplatelet strategies may need to be considered 1

Potential Pitfalls and Caveats

• Avoid administering clopidogrel without a loading dose, as this will delay the antiplatelet effect 1
• Be aware that clopidogrel efficacy may be affected by CYP2C19 genetic polymorphisms, which can reduce the formation of its active metabolite 1
• Consider patient compliance factors, as clopidogrel's once-daily dosing may offer an advantage over ticagrelor's twice-daily regimen 2
• Ensure that intracranial hemorrhage has been ruled out on neuroimaging before initiating any antiplatelet therapy 3