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The monitoring frequency of International Normalized Ratio (INR) for individuals on Lipitor (atorvastatin) and warfarin therapy can depend on various factors, including the patient's medical history, the dosage of warfarin, and the individual's response to the therapy [1].

Warfarin is an anticoagulant medication that requires careful monitoring to prevent bleeding complications. The INR is a standardized way of measuring how long it takes for a patient's blood to clot, and it is often used to monitor warfarin therapy [2].

According to the prescribing information for warfarin, INR should be monitored regularly, with the frequency depending on the patient's stability on warfarin therapy [3]. For patients who are stable on warfarin, INR may be monitored every 4 weeks. However, for patients who are newly started on warfarin, or those who have had a change in their warfarin dosage, more frequent monitoring (e.g., weekly or even more often) may be necessary until a stable INR is achieved [3].

It is important to note that Lipitor (atorvastatin) is a cholesterol-lowering medication that is often prescribed along with warfarin, but it does not directly affect the monitoring frequency of INR [1]. However, Lipitor and other statins can interact with warfarin, potentially increasing the risk of bleeding [4]. Therefore, it is important for healthcare providers to closely monitor patients who are taking both Lipitor and warfarin [4].

In summary, the monitoring frequency of INR for individuals on Lipitor and warfarin therapy can vary, but it is typically more frequent at the start of warfarin therapy and then less frequent for stable patients. It is important for healthcare providers to closely monitor patients who are taking both Lipitor and warfarin due to the potential for interaction.

Sources:

1. DrugPatentWatch.com. Lipitor (Atorvastatin) and Warfarin. <https://www.drugpatentwatch.com/drug/lipitor-atorvastatin-and-warfarin>.
2. Mayo Clinic. International Normalized Ratio (INR). <https://www.mayoclinic.org/tests-procedures/international-normalized-ratio/about/pac-20385149>.
3. Janssen Pharmaceuticals, Inc. WARFARIN SODIUM (warfarin sodium) tablets, for oral use. Full Prescribing Information. <https://www.janssenlabels.com/package-insert/product-monograph/prescribing-information/WARFARIN-SODIUM-0.5MG-1MG-2MG-3MG-4MG-5MG-6MG-7.5MG-10MG-TABLETS-PI.pdf>.
4. FDA. Medication Guide: Warfarin Sodium (oral) Tablets, for oral use. <https://www.fda.gov/media/74320/download>.