Why does inr drop

Your Email Address. Send Email. Donate today. Updated November After being diagnosed with a blood clot thrombosis , your healthcare provider may prescribe warfarin for treatment. What does INR stand for?

How often is testing needed? What can I do to help keep my INR level where it should be? Looking forward Starting a new medication can be challenging and warfarin is no exception. Previous Post. All Posts. Measurements: Serial plasma samples were drawn for INR measurements approximately 20, 65, , and hours after patients received the last dose of warfarin. In five patients, INR was measured twice daily for 5 days.

Results: For patients with a mean steady-state INR of 2. Some experts would continue the current dosage for a period of time, while others would reduce the total weekly dosage by 2 to 18 percent.

Banet and associates evaluated the safety of not changing the warfarin dosage because of a mildly elevated INR and quantified the relationship between reduction of the warfarin dosage and subsequent decrease of the INR. The study was a randomized controlled trial of outpatients who were receiving warfarin therapy at eight health maintenance centers.

Investigators identified patients who had a mildly elevated INR between 3. To be included in the study, the patients had to be asymptomatic, have been using warfarin for at least 30 days, and have a previous therapeutic INR 2. Four of the centers were randomized to have access to a telephone-based anticoagulation service, and at the other four centers, patients continued to be managed by their primary care physicians.

The difference between the two groups was that the anticoagulation service had an established protocol that patients with mildly elevated INRs were to be maintained on the same dosage unless it was clinically indicated to reduce the dosage, while the primary care group had no established protocol. In addition, the anticoagulation service telephoned every patient who had an elevated INR and asked about any potential cause for the increase and assessed any risk for bleeding.

The warfarin dosage, and the time and value of the follow-up INR were recorded for analysis. Adverse events were recorded for the anticoagulation group. A cohort of patients 41 percent were women; mean age: 72 years was analyzed for the study, with of those in the anticoagulation service group. The anticoagulation service group had only one episode of epistaxis in the 30 days after the elevated INR. So, you begin to see the effects of a skipped or adjusted dose start within a day and peak at about five days.

Did the patient start, stop or change any other medications? There are two primary ways that such medications interact with warfarin and therefore INR:. Inducers — Medications that induce, or rev up, this metabolic pathway increase warfarin metabolism rendering the med less effective.

So, INR decreases. Inhibitors — Inhibitors block or slow the pathway that metabolizes warfarin so the drug builds up in the system and circulates longer. With warfarin metabolism decreased i. Inhibitors are more common than inducers. The length of this effect depends on the half-life of the inhibiting drug and can range from a day or two to months ex. This includes over-the-counter meds and substances like herbal remedies and supplements ginko biloba, garlic and ginseng are common offenders.

Interestingly, acute illness can have an effect on INR. Patients with vomiting and diarrhea, for example, may decrease vitamin K consumption and absorption throwing off INR as discussed below. Even an acute upper respiratory infection can alter hepatic oxygenation affecting warfarin metabolism in the liver.

As a general rule, you should be on the lookout for an INR increase in the case of acute illness. Does the patient have an exacerbation or change in a chronic condition? Chronic disease plays a role in anticoagulant management as well. Congestive Heart Failure CHF — Congestive heart failure can cause congestion of blood flow in the liver where warfarin is metabolized.