What is the loading dose of Plavix (clopidogrel) when switching from ticagrelor?

Loading Dose of Clopidogrel When Switching from Ticagrelor

When switching from ticagrelor to clopidogrel (Plavix), a loading dose of 600 mg of clopidogrel should be administered after ticagrelor is discontinued, followed by the standard maintenance dose of 75 mg daily. 1

Rationale for Loading Dose

• Ticagrelor is a more potent P2Y12 inhibitor with a different binding mechanism than clopidogrel, binding to the receptor at a location distinct from the ADP binding site 1
• Ticagrelor has a faster onset of action and achieves greater platelet inhibition than clopidogrel, with peak inhibitory effect seen about 2 hours after administration 1, 2
• When switching from a more potent agent (ticagrelor) to a less potent one (clopidogrel), a loading dose helps achieve adequate platelet inhibition more quickly 1
• The 600 mg loading dose of clopidogrel is recommended to achieve faster and more consistent platelet inhibition compared to the 300 mg dose 1

Timing of Administration

• Clopidogrel loading dose should be administered after ticagrelor is discontinued 1
• Unlike switching from clopidogrel to ticagrelor (where immediate switching with loading dose is recommended), switching from ticagrelor to clopidogrel requires consideration of ticagrelor's offset time 1, 2
• Ticagrelor has a faster offset than clopidogrel, with platelet function beginning to recover within 24-48 hours after discontinuation 2

Clinical Considerations

• Patients switching from ticagrelor to clopidogrel may have a temporary reduction in antiplatelet effect during the transition period 3
• The RESPOND study demonstrated that switching from ticagrelor to clopidogrel results in increased platelet aggregation (from 36±14% to 56±9%), indicating a reduction in platelet inhibition 3
• Clopidogrel requires hepatic conversion to an active metabolite, unlike ticagrelor which is directly active, leading to more variable response among patients 1
• Consider that approximately 15-30% of patients may be poor responders to clopidogrel due to genetic polymorphisms affecting its metabolism 3

Special Populations

• In patients aged 70 years or older, clopidogrel may be preferred over ticagrelor due to lower bleeding risk, as demonstrated in the POPular AGE trial 4
• For patients with high bleeding risk, careful monitoring during the transition period is recommended 1, 4
• Patients taking proton pump inhibitors may have reduced antiplatelet effects with clopidogrel but not with ticagrelor 5

Practical Approach to Switching

1. Discontinue ticagrelor
2. Administer 600 mg loading dose of clopidogrel 1
3. Continue with 75 mg daily maintenance dose of clopidogrel 1
4. Monitor for any signs of thrombotic events during the transition period 3

Remember that dual antiplatelet therapy duration should generally be maintained for 12 months in patients with acute coronary syndrome unless there are contraindications such as excessive bleeding risk 1.