I saw this post on what affects warfarin , it seems tk interact with everything’s
What ever a person does or does not do to effect their INR will not make any difference to the stability or its continuity at target, therefore I would suggest people get to know what and how INR is effected, then alter their dose to suite their bodies and lifestyle needs.
INR 101 - possible influences on INR:
• Warfarin, the shorter the ½ life of the coumarin / warfarin brand used the more unstable an individual's INR will be. Those on low daily dosage of Warfarin are also more unstable than those on higher doses.
• Drugs, prescription drugs [Antibiotics, Cardiac, Anti-inflammatory or Analgesics (pain relieving ability), Statins etc.] or over the counter drugs; mainly potentiate the effects of Warfarin [increase the INR] or have no effect a few reduce the INR. It depends on how / if they are metabolised in the liver by the Enzymes CPY450 and which pathways. Warfarin is metabolised on enzyme CPY450: pathways 1A1, 1A2, 2C8, 2C9, 2C18, 2C19, 3A4, which is why it interacts with so many other drugs.
Broad-spectrum antibiotics can reduce the amount of the normal bacterial flora in the bowel, which make significant quantities of vitamin K1, thus potentiating the effect of Warfarin.
• Alcohol, daily moderate alcohol use (1 or 2 units - no more) has little effect on the INR.
It can increase or decrease how fast your body metabolizes warfarin. Whether it increases or decreases your warfarin metabolism may depend on how much you drink, how often you drink, and whether the alcohol has damaged your liver. Intermittent, occasional or binge drinking has a double whammy effect initially raising the INR then because your liver was working overtime processing all the alcohol, when it has finished it processes the warfarin at a faster rate and your INR dips lower increasing your risk of clotting.
Daily alcohol use of greater than three or more units will result in the possibility of several thing happening. First, the enzymes that metabolize the Warfarin can become more active. This means that the INR test will show that you are not taking enough Warfarin. Then your Warfarin dose will be increased. Should you suddenly stop drinking, the INR will shoot upward and increase your risk of bleeding. Additionally, alcohol irritates the lining of your stomach and this may cause internal bleeding.
• Vitamin supplements (Vitamin K, ½ life 12 hours, reduces the effects of Warfarin, rendering the medication ineffective with but 1-2mg of oral dosing, you would need to be on a cabbage diet to see significant reductions in INR. Recent information has indicated that a healthy intake of vitamin K may actually help to improve the stability of Warfarin therapy as measured by the INR and is required for healthy bones. Vitamin C could interfere with the effectiveness of Warfarin medication, do not exceed the RDA. Vitamin E potentiates the effects of Warfarin and increase the INR),
• High Protein Diets can also affect the way warfarin works in your body. Some of your Warfarin binds to protein in your bloodstream. While warfarin is attached to this protein, it has no effect on your body. It’s thought that high protein diets can increase the amount of proteins in your body and cause more Warfarin to be bound to protein. This causes a decrease in available warfarin and therefore your INR will decrease,
• Minerals supplements (Some, such as Iodine by altering thyroid metabolism of vitamin K, reduce INR),
• Herbs supplements (prescription or over the counter; that interact with Warfarin mainly increase INR, even innocents such as garlic).
• Food, some foods such as Grapefruit Juice (>680ml / day) and Cranberry juice (>200ml / day) may increase the blood levels of drugs, including some statins, which may potentiate the effects of warfarin and increase the INR, they may also cause liver/kidney damage if levels get out of control. Grapefruit juice contains a substance (not well determined) that seems to be responsible for drug interactions), it is thought that these interactions are with the flavonoids it contains that can inhibit CYP450 isoenzymes (pathways 3A4, 2C9, 2C19, and 1A2), because every juice brand and the cocktail of drugs individuals are taking are different these interactions are difficult to predict.
• Freezing food ruptures its cell walls and so when the food is prepared and eaten the availability of nutrients such as vitamin k is doubled. Adding fat or oil to fat soluble vitamin rich foods triples their absorption into the blood serum.
• Colds/Flu (increase liver metabolisation therefore decreases INR),
• Diarrhoea may cause the INR to increase. The bacteria in the intestinal tract produce vitamin K, with diarrhoea these bacteria are often washed out of the intestine. Therefore, the vitamin K they would have produced is not available.
• Thyroid activity (Hyper increase INR or Hypo decrease INR - The thyroid is involved in metabolism of vitamin K dependent clotting factors. Warfarin works by slowing the production of these clotting factors. These two factors appear to be in a very delicate balance),
• Liver function (when there is fluid retention, the liver also becomes congested and blood does not flow through it very well. If a "water pills" are taken, the INR may suddenly decrease, if anything effects the liver it effects the INR),
• Altitude (>2400 meters decreases INR by approx 0.7),
• Exercise decreases INR significantly. 20mins to 2hrs of exercise @ >65% to 85% of max heart rate may result in required dosage increases of between 2mg and doubling your dose on exercise days respectively to maintain your INR with increased activity levels,
• Weight, individuals that are underweight (BMI < 20) generally have less stable and are more frequently out of range INRs. Obese people (BMI >30) generally are more frequently out of range INRs the reasons being due to many of the above.
There are so many things that can affect the INR, that it is unusual if it is the same for two consecutive readings. It is affected by, the time between when doses were taken and the time blood is drawn, if blood is drawn in a syringe the amount of blood drawn as the tube contains anti clotting agents. What you ate over the past several days, other medications, physical activity, fever, age, type of warfarins and their ½ lives (If the half-life of the drug equals 1 day, then the effect of the drug after 1 day will be the equivalent of an average dose of one pill per day, whereas after two days the effect will be the equivalent of 1.5 pills per day. Only after several days will the effect of the average or effective dosage approximate the effect of a long-term treatment of two pills per day), liver function, poor diet, sickness, fever, genotype giving genetic warfarin resistance and things that are not even known about. Starting an interacting drug. Stopping an interacting drug. Change in eating habits. Stopping things including food that contain vitamin K. Change in exercise levels (if you become ill, have surgery etc. you do not get your heart rate up to its previous levels. Since Warfarin is only metabolized when the blood carrying it passes through the liver, a lower heart rate means less Warfarin metabolised. This is like increasing the dose). To top it all off, if your measurements are taken at different clinics, hospitals or self tested for any reason, the measurements may vary from each other by as much as +/- 0.5 INR especially at higher INRs.
Any individual can map their own personal sensitivity polynomial response curve to warfarin and how it effects their INR with the help of their healthcare providers.
