Can certain foods and beverages make warfarin less effective?
However, certain foods and beverages can make warfarin less effective in preventing blood clots. It's important to pay attention to what you eat while taking warfarin. One nutrient that can lessen warfarin's effectiveness is vitamin K. It's important to be consistent in how much vitamin K you get daily.
What factors affect the initial dose of warfarin?
Not all factors responsible for Warfarin dose variability are known, and the initial dose is influenced by: Clinical factors including age, race, body weight, sex, concomitant medications, and comorbidities Genetic factors (CYP2C9 and VKORC1 genotypes) [see Clinical Pharmacology (12.5)]
What is warfarin used to treat?
Warfarin is an anticoagulant drug that can be taken orally for the treatment of thrombotic conditions such as deep vein thrombosis, or to prevent the risk of thrombus formation in patients who have recently had a myocardial infarction (MI) or who have atrial fibrillation (AF).
How is warfarin metabolized in the body?
Warfarin is stereoselectively metabolized by hepatic cytochrome P-450 (CYP450) microsomal enzymes to inactive hydroxylated metabolites (predominant route) and by reductases to reduced metabolites (Warfarin alcohols) with minimal anticoagulant activity.
Which group of medications would be detrimental if used to treat a patient who has heart failure?
Drugs that can exacerbate heart failure should be avoided, such as nonsteroidal anti-inflammatory drugs (NSAIDs), calcium channel blockers (CCBs), and most antiarrhythmic drugs (except class III).
Which class of medication is frequently used to improve long term outcomes in patients with systolic dysfunction?
ACE inhibitors also have been found to significantly increase survival in patients with systolic HF at long-term follow-up by 27% (45), by 28% (46), by 16% (47), and by 27% (48) and should be used to treat patients with systolic HF (Table 1) (1).
Which patient could be expected to have the highest systolic blood pressure?
Older people are more likely to have it, because systolic blood pressure usually goes up as you age. More than 30% of women over 65 and more than 20% of men have this condition. If your parents had high blood pressure, you may be more likely to have it.
Which laboratory abnormality may be observed in a patient who takes chlorthalidone?
Chlorthalidone may raise the serum uric acid level due to reduced clearance of uric acid and may cause or exacerbate hyperuricemia and precipitate gout in susceptible patients.
Which class of drugs are best in controlling hypertension in a patient who had a recent experience of heart failure?
Thiazides are widely used as first-line therapy for hypertension. In patients with HF, the more potent loop diuretics are preferred.
Which of the following drugs can help reduce mortality in patients with HF?
BETA BLOCKER Beta blockers, such as bisoprolol (Zebeta), carvedilol (Coreg), and metoprolol succinate (Toprol XL), are effective at reducing mortality in patients with symptomatic heart failure when combined with ACE inhibitors.
Which is more important systolic or diastolic blood pressure?
Over the years, research has found that both numbers are equally important in monitoring heart health. However, most studies show a greater risk of stroke and heart disease related to higher systolic pressures compared with elevated diastolic pressures.
What is the main cause of high blood pressure?
Common factors that can lead to high blood pressure include: A diet high in salt, fat, and/or cholesterol. Chronic conditions such as kidney and hormone problems, diabetes, and high cholesterol. Family history, especially if your parents or other close relatives have high blood pressure.
What causes the top number of blood pressure to be high?
Isolated systolic hypertension is when your systolic blood pressure is high, but your diastolic blood pressure is normal. It can occur naturally with age or can be caused by specific health conditions, including anemia, diabetes, and hyperthyroidism.
Why do diuretics cause hypokalemia?
Diuretics are commonly used to treat high blood pressure (hypertension). They lower blood pressure by helping the body eliminate sodium and water through the urine. However, some diuretics can also cause the body to eliminate more potassium in the urine. This can lead to low potassium levels in the blood (hypokalemia).
Does chlorthalidone cause hyperkalemia?
The incidence of hyperkalemia (serum K 5.4 mmol/L) was 1.2% in chlorthalidone-, 3.6% in lisinopril-, and 1.9% in amlodipine- treated groups. Overall, hypokalemic patients did not experience greater rates of CHD or a combined CVD end point.
Why should you monitor intake and output with diuresis?
Why do we monitor patients taking diuretics and what do we monitor? Monitoring a person on diuretics is necessary to assess response to treatment and to prevent adverse events, particularly electrolyte imbalances and decline in renal function (see Tables 1 and 2).
What is the mechanism of action of warfarin?
Warfarin acts by inhibiting the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and the anticoagulant proteins C and S. Vitamin K is an essential cofactor for the post ribosomal synthesis of the vitamin K-dependent clotting factors.
How does warfarin interact with other drugs?
Drugs may interact with Warfarin sodium through pharmacodynamic or pharmacokinetic mechanisms. Pharmacodynamic mechanisms for drug interactions with Warfarin sodium are synergism (impaired hemostasis, reduced clotting factor synthesis), competitive antagonism (vitamin K), and alteration of the physiologic control loop for vitamin K metabolism (hereditary resistance). Pharmacokinetic mechanisms for drug interactions with Warfarin sodium are mainly enzyme induction, enzyme inhibition, and reduced plasma protein binding. It is important to note that some drugs may interact by more than one mechanism.
What is the WARIS study?
WARIS (The Warfarin Re-Infarction Study) was a double-blind, randomized study of 1214 patients 2 to 4 weeks post-infarction treated with Warfarin to a target INR of 2.8 to 4.8. The primary endpoint was a composite of total mortality and recurrent infarction. A secondary endpoint of cerebrovascular events was assessed. Mean follow-up of the patients was 37 months. The results for each endpoint separately, including an analysis of vascular death, are provided in Table 7.
How long after heparin injection should INR be monitored?
As heparin may affect the INR, patients receiving both heparin and Warfarin sodium should have INR monitoring at least: 5 hours after the last intravenous bolus dose of heparin, or. 4 hours after cessation of a continuous intravenous infusion of heparin, or. 24 hours after the last subcutaneous heparin injection.
What is the chemical formula for warfarin sodium?
The chemical name of Warfarin sodium is 3- (α-acetonylbenzyl)-4-hydroxycoumarin sodium salt , which is a racemic mixture of the R - and S -enantiomers. Crystalline Warfarin sodium is an isopropanol clathrate. Its empirical formula is C 19 H 15 NaO 4, and its structural formula is represented by the following:
How long does Warfarin stay in your system?
The anticoagulant effect of Warfarin sodium persists beyond 24 hours. If a patient misses a dose of Warfarin sodium at the intended time of day, the patient should take the dose as soon as possible on the same day. The patient should not double the dose the next day to make up for a missed dose.
What enzymes are involved in the metabolization of warfarin?
Warfarin is stereoselectively metabolized by hepatic cytochrome P-450 (CYP450) microsomal enzymes to inactive hydroxylated metabolites (predominant route) and by reductases to reduced metabolites (Warfarin alcohols) with minimal anticoagulant activity.
What is the purpose of taking Warfarin?
Warfarin (also known as Coumadin, Jantoven, Marevan, or Uniwarfin) is an anticoagulant used to prevent the formation of blood clots and their migration in the body.
What is warfarin used for?
Warfarin is a drug that is widely used to prevent blood clotting, for example in people at risk of heart attacks or strokes (10. From: Clinical Trials, 2012. Download as PDF.
What enzyme metabolizes warfarin?
However, considerable variability in the warfarin dose–response relationship between individuals is explained mainly by genetic polymorphisms of CYP2C9, the major enzyme that metabolizes warfarin and its target receptor, vitamin K epoxide reductase complex (VKORC1).
Why is warfarin resistant?
It is worth noting that resistance to warfarin therapy is usually due to excessive vitamin K intake from diet or supplements. However, hereditary warfarin resistance because of mutations in vitamin K epoxide reductase complex subunit 1,have also been reported. Conversely, variant CYP2C9 alleles (one of the P450 hepatic microsomal enzymes that inactivate warfarin) may enhance sensitivity to warfarin.
How is warfarin absorbed?
Warfarin is rapidly and nearly completely absorbed by the oral route. Peak plasma levels typically occur within 2–8 h. Warfarin is highly protein bound: 97–99%. The volume of distribution approximates 0.15 l kg −1. Warfarin is extensively metabolized by hepatic microsomal enzymes. The primary metabolites are 6- and 7-hydroxy warfarin via oxidation and several warfarin alcohols via reduction. The warfarin alcohols retain weak anticoagulant activity. The metabolites undergo enterohepatic circulation. Approximately 85% of warfarin appears in the urine as metabolites. Less than 1% or 2% appears in the urine unchanged. Warfarin metabolites are also excreted in the stool. The plasma half-life varies widely, from 10 to 80 h; it is typically 36–44 h. The duration of clinical effects can significantly exceed the half-life of warfarin. (Note: There are many drug interactions with warfarin; the reader is referred to a standard pharmacology text for further details.)
How long does warfarin stay in your blood?
Levels of warfarin in the blood peak about 90 minutes after drug administration. Racemic warfarin has a plasma half-life of 36 to 42 hours, and over 97% of circulating warfarin is bound to albumin. Only unbound warfarin is biologically active.
Why is coagulation monitoring important?
A wide variety of drugs can alter absorption, clearance, or metabolism of warfarin. Because of the variability in the anticoagulant response to warfarin, coagulation monitoring is essential to ensure that a therapeutic response is obtained. View chapter Purchase book. Read full chapter.
Why is warfarin called an anticoagulant?
Because warfarin interferes with the formation of blood clots, it is called an anticoagulant (PDF). Many people refer to anticoagulants as *blood thinners; however, warfarin does not thin the blood but instead causes the blood to take longer to form a clot.
How to reduce bleeding while taking warfarin?
Some simple changes to decrease the risk of bleeding while taking warfarin include the following: Use a soft-bristle toothbrush. Floss with waxed floss rather than unwaxed floss. Shave with an electric razor rather than a blade. Take care when using sharp objects, such as knives and scissors.
How does warfarin affect blood clotting?
The goal of warfarin therapy is to decrease the clotting tendency of blood, not to prevent clotting completely. Therefore, the effect of warfarin must be monitored carefully with blood testing. On the basis of the results of the blood test, your daily dose of warfarin will be adjusted to keep your clotting time within a target range. The blood test used to measure the time it takes for blood to clot is referred to as a prothrombin time test, or protime (PT). The PT is reported as the International Normalized Ratio (INR).
What is the INR of a PT?
The INR is a standardized way of expressing the PT value. The INR ensures that PT results obtained by different laboratories can be compared. It is important to monitor the INR (at least once a month and sometimes as often as twice weekly) to make sure that the level of warfarin remains in the effective range. If the INR is too low, blood clots will not be prevented, but if the INR is too high, there is an increased risk of bleeding. This is why those who take warfarin must have their blood tested so frequently.
What to wear for warfarin?
Wear Medical Identification. Those who require long-term warfarin should wear a medical alert bracelet, necklace, or similar alert tag at all times. If an accident occurs and the person is too ill to communicate, a medical alert tag will help responders provide appropriate care.
Does warfarin help with blood clots?
Warfarin decreases the body’s ability to form blood clots by blocking the formation of vitamin K–dependent clotting factors. Vitamin K is needed to make clotting factors and prevent bleeding. Therefore, by giving a medication that blocks the clotting factors, your body can stop harmful clots from forming and prevent clots from getting larger.
Why are generic drugs less expensive than brand names?
Generic drugs are often less expensive than their brand-name counterparts, because the generic manufacturers have not incurred the expenses of developing and marketing a new drug.
Why do food and drugs interact?
Interactions between food and drugs may inadvertently reduce or increase the drug effect. Some commonly used herbs, fruits as well as alcohol may cause failure of the therapy up a point of to serious alterations of the patient’s health. The majority of clinically relevant food-drug interactions are caused by food-induced changes in the bioavailability of the drug.
How do drug interactions affect the pharmacokinetics of a drug?
Drug interactions can alter the pharmacokinetics and/or pharmacodynamics of a drug. The pharmacodynamic interaction may be additive, synergistic, or antagonistic effects of a drug. Drug interactions (DIs) represent an important and widely under recognized source of medication errors.5The gastrointestinal absorption of drugs may be affected by the concurrent use of other agents that,1have a large surface area upon which the drug can be absorbed,2bind or chelate,3alter gastric pH,4alter gastrointestinal motility, or affect transport proteins such as P-glycoprotein. A reduction only in absorption rate of a drug is seldom clinically important, whereas a reduction in the extent of absorption will be clinically important if it results in sub therapeutic serum levels.5
How do drugs show their efficacy?
Drugs can show their efficacy only if administered in appropriate quantity with appropriate combination of drugs and foods and at appropriate time. In contrast to the easy access to information on drug-drug interactions, the information about food-drug interaction is not always available conveniently.
What is the interaction between natural products and drugs?
The interaction of natural products and drugs is a common hidden problem encountered in clinical practice. The interactions between natural products and drugs are based on the same pharmacokinetic and pharmacodynamic principles as drug-drug interactions.
Why are drug interactions bad?
Generally speaking, drug interactions are to be avoided, due to the possibility of poor or unexpected outcomes.
What are clinically significant drug interactions?
Clinically significant drug interactions, which pose potential harm to the patient, may result from changes in pharmaceutical, pharmacokinetic, or pharmacodynamic properties. Some may be taken advantage of, to the benefit of patients, but more commonly drug interactions result in adverse drug events.
Why is CoQ10 used in food?
Factors such as nonspecific binding, atypical kinetics, poor effector solubility, and varying ratios of accessory proteins may alter the kinetic behavior of an enzyme and subsequently confound the extrapolation of in vitro data to the human situation.6Coenzyme Q-10 (CoQ10) is very widely consumed by humans as a food supplement because of its recognition by the public as an important nutrient in supporting human health. It interferes with intestinal efflux transporter P-glycoprotein (P-gp) and as result food-drug interactions arise.7
What is the effect of calcium carbonate and sucralfate on warfarin?
Sucralfate and calcium carbonate. Sucralfate and calcium carbonate decrease absorption of warfarin
What is the blood pressure of a 40 year old African American?
40 year-old African American patient has blood pressure readings of 175/100 and 170/102. What is a reasonable plan of care for this patient today?
How to remember to take medication?
Take medication at the same time each day to help you remember to take it.
Why is it important to have a PT/INR checked?
It is very important to have the PT/INR checked to monitor safety and adjust dosages. Doses of your medication can occasionally change.
Can you take aspirin with warfarin?
DO NOT use aspirin or other NSAIDs. Check labels of all OTC products carefully before use. Many cough and cold products contain aspirin and/or NSAIDs. DO NOT use other blood thinners, garlic, ginseng, ginkgo, vitamin E, or other herbals without talking to your doctor first. Over 60 herbal therapies have anti platelet effects or may interact with warfarin in other ways. DO NOT start any herbal therapy without talking to your prescriber or pharmacist.
What do I need to know about my diet?
Some foods you eat affect the way warfarin works in your body. Try and keep eating what you normally do. It is most important to eat a healthy, consistent, and balanced diet.
What is high in vitamin K?
The most common foods that have high vitamin K are green leafy vegetables such as kale, collard greens, broccoli, spinach, cabbage, and lettuce.
Vitamin K foods
It is important to try and keep the same amount of vitamin K in your diet. All foods are okay, but do not make big changes to how much or what you eat. It is important to check with your health-care provider before making any big changes to your diet.
Indications and Usage For Warfarin
Warfarin Dosage and Administration
Contraindications
Warnings and Precautions
Adverse Reactions
Drug Interactions
- General Information
Drugs may interact with Warfarin sodium through pharmacodynamic or pharmacokinetic mechanisms. Pharmacodynamic mechanisms for drug interactions with Warfarin sodium are synergism (impaired hemostasis, reduced clotting factor synthesis), competitive antagonism (vi… - CYP450 Interactions
CYP450 isozymes involved in the metabolism of Warfarin include CYP2C9, 2C19, 2C8, 2C18, 1A2, and 3A4. The more potent Warfarin S-enantiomer is metabolized by CYP2C9 while the R-enantiomer is metabolized by CYP1A2 and 3A4. • 1. Inhibitors of CYP2C9, 1A2, and/or 3A4 have …
Use in Specific Populations
Overdosage
Warfarin Description
Warfarin - Clinical Pharmacology
Overview
Mechanism
Treatment
Purpose
Administration
Risks
Diagnosis
Significance
Contraindications
Preparation
Interactions
- Patients who take warfarin should consult with their healthcare provider before taking any new medication, including over-the-counter (nonprescription) drugs, herbal medicines, vitamins or any other products. Many medications can alter the effectiveness of warfarin, resulting in an INR that is either too high or too low. Some of the most common ove...