Can you load with Plavix (clopidogrel) 300mg if you have already taken Brilinta (ticagrelor) 90mg once this morning?

Switching from Ticagrelor to Clopidogrel: Loading Dose Considerations

You should not administer a 300mg loading dose of clopidogrel if you have already taken ticagrelor 90mg earlier the same day due to increased bleeding risk without additional anti-platelet benefit.

Rationale for This Recommendation

Ticagrelor is a potent P2Y12 receptor inhibitor with a rapid onset of action, achieving significant platelet inhibition within 30 minutes of administration 1. When a patient has already received a dose of ticagrelor (90mg), adding a loading dose of clopidogrel (300mg) would:

1. Provide no additional anti-platelet benefit, as ticagrelor already provides more potent platelet inhibition than clopidogrel
2. Potentially increase bleeding risk by combining two different P2Y12 inhibitors

Pharmacological Considerations

Ticagrelor Properties

• Achieves significant platelet inhibition within 30 minutes, with peak effect at approximately 2 hours 1
• Has a half-life of 6-12 hours for the parent drug 1
• Provides more potent and consistent platelet inhibition than clopidogrel 2

Switching Between P2Y12 Inhibitors

When switching between P2Y12 inhibitors, guidelines recommend:

• When switching from clopidogrel to ticagrelor: Patients should receive the full 180mg loading dose of ticagrelor regardless of prior clopidogrel therapy 1, 3
• When switching from ticagrelor to clopidogrel: No loading dose is typically recommended if the patient has recently received ticagrelor

Clinical Evidence

The PLATO trial demonstrated that ticagrelor's benefits were observed regardless of prior clopidogrel therapy, with 47% of patients receiving clopidogrel at randomization 1, 2. This suggests that ticagrelor provides adequate platelet inhibition even in patients previously treated with clopidogrel.

Proper Approach to Switching

If a clinical decision has been made to switch from ticagrelor to clopidogrel:

1. Wait at least 24 hours after the last ticagrelor dose
2. Then initiate clopidogrel with a 75mg maintenance dose (not a loading dose)
3. Continue daily clopidogrel 75mg as prescribed

Important Considerations and Cautions

• Bleeding risk: Combining multiple antiplatelet agents increases bleeding risk
• Rebound effect: Abrupt discontinuation of ticagrelor without appropriate coverage could theoretically increase thrombotic risk
• Clinical indication: The reason for switching should be carefully considered, as ticagrelor has demonstrated superior efficacy in reducing cardiovascular events compared to clopidogrel in acute coronary syndrome 2

Special Situations

If immediate high-level platelet inhibition is required for a high-risk procedure while on ticagrelor:

• Continue ticagrelor rather than switching to clopidogrel
• If switching is absolutely necessary, consult with a cardiologist regarding the timing and dosing strategy

Remember that both medications require concomitant low-dose aspirin therapy, with 81mg daily being the recommended dose for use with ticagrelor 1.