From the Guidelines
Loading Dose of Aspirin and Plavix (Clopidogrel)
The loading dose of aspirin is typically 325 mg, and for clopidogrel (Plavix), it is 600 mg 1. This high initial dose helps achieve rapid platelet inhibition, which is crucial in acute coronary syndromes or before certain cardiac procedures.
- The choice of loading dose is based on evidence from studies such as the CURRENT-OASIS 7 trial, which compared different doses of aspirin and found that a higher dose did not necessarily translate to better outcomes but did increase the risk of bleeding 1.
- For clopidogrel, a loading dose of 600 mg is preferred over 300 mg due to its more extensive and rapid platelet inhibition, as supported by the CURRENT-OASIS 7 subgroup analysis and the ARMYDA-6 MI study 1.
- It's essential to assess individual patient factors, such as renal function and bleeding risk, before initiating therapy, as these can influence the choice of loading dose and maintenance therapy.
- Maintenance doses after the initial loading dose are typically 75 mg to 100 mg daily for aspirin and 75 mg daily for clopidogrel, with the duration of therapy depending on the specific clinical context, such as the type of stent used in PCI 1.
Key Considerations
- Bleeding Risk: Higher doses of aspirin increase the risk of bleeding, making the choice of loading and maintenance doses critical in balancing efficacy and safety 1.
- Patient Factors: Individual patient characteristics, including renal function, diabetes, and genetic polymorphisms affecting drug metabolism (e.g., CYP2C19 for clopidogrel), can influence the response to antiplatelet therapy and should be considered when selecting doses 1.
- Clinical Context: The specific clinical scenario, such as acute coronary syndrome, PCI with stent placement, or the need for urgent antiplatelet therapy, guides the selection of loading and maintenance doses for aspirin and clopidogrel 1.
From the Research
Loading Dose of Aspirin and Plavix (Clopidogrel)
- The loading dose of aspirin is 250-500 mg, followed by 75-100 mg/day 2.
- The loading dose of clopidogrel is 600 mg, and in patients with ACS and percutaneous coronary intervention (PCI), 2 × 75 mg clopidogrel should be given daily over 7 days, while in all other patients 75 mg per day appears to be sufficient 2.
- Another study suggests that a 300-mg loading dose of clopidogrel must be administered at least 15 hours prior to PCI, or a 600-mg loading dose can be used with 2 hours of pretreatment 3.
- A study on clopidogrel reloading found that a new loading dose of 900 mg improves platelet inhibition and reduces poor response to clopidogrel significantly more than 300 or 600 mg 4.
- The current status of antiplatelet therapy in acute coronary syndrome recommends a loading dose of 600 mg of clopidogrel, and options for increasing loading and maintenance doses or changing to new antiplatelet agents like prasugrel and ticagrelor are being considered 5.
Resistance to Antiplatelet Agents
- A study found that 12.5% of patients with acute coronary syndrome showed resistance to the antiplatelet effects of both aspirin and clopidogrel in conventional doses, highlighting the need for further research on this issue 6.