Warfarin

Jantoven is labeled for prevention/treatment of venous thrombosis and pulmonary embolism; prevention/treatment of thromboembolic complications associated with AF or cardiac valve replacement; and reduction of death, recurrent MI and thromboembolic events after MI. The post-MI indication is not a recommendation for routine anticoagulation in every MI survivor.

For AF, use current validated stroke-risk assessment rather than the label’s older risk-factor algorithm. DOACs are generally preferred for eligible AF patients; mechanical valves and clinically important mitral stenosis require separate VKA pathways. Mechanical valves require VKA therapy. ASH generally favors DOACs for non-cancer VTE, with exceptions determined by the clinical situation.

This profile gives representative adult INR contexts, not a self-adjustment algorithm. Pediatric treatment, pregnancy with mechanical valves, anticoagulant conversions, post-MI combination therapy and procedures require specialist plans. Anticoagulant choice, duration and antiplatelet exposure must be reassessed individually.

Without genotype guidance, the label describes a usual initial 2–5 mg once daily and typical maintenance 2–10 mg daily, adjusted to INR response. Lower initial/maintenance doses may be appropriate in older or debilitated people and some Asian patients. Routine loading is not recommended. CYP2C9/VKORC1 results, when known, can inform the initial estimate but do not replace INR testing.

For acute DVT/PE when a VKA is selected, ASH specifies overlap with UFH or LMWH for at least 5 days and until therapeutic INR has been achieved for 24 hours. Primary treatment is generally 3–6 months; transiently provoked events often stop thereafter, while unprovoked/chronic-risk or recurrent unprovoked disease may need indefinite secondary prevention after bleeding-risk review. Cancer-associated VTE and other indications need separate guidance.

The label calls for daily INR during initiation until stable, then typically every 1–4 weeks, with extra checks after medicine, diet or clinical changes. A missed dose may be taken when remembered on the same day; do not double the next day. Plan surgery/dental work and any interruption or bridging with the treating team; never apply one universal bridge or conversion rule.

The label contraindicates pregnancy except the specified high-risk mechanical-valve situation; hemorrhagic tendencies/blood dyscrasias; active ulceration or overt GI/GU/respiratory bleeding; CNS hemorrhage; cerebral/dissecting-aortic aneurysm; pericarditis/effusion; bacterial endocarditis; threatened abortion, eclampsia or preeclampsia; relevant recent/contemplated CNS/eye or extensive traumatic surgery; spinal puncture or procedures risking uncontrollable bleeding; major regional/lumbar block anesthesia; malignant hypertension; hypersensitivity; and unsupervised patients with a high likelihood of nonadherence.

Warfarin can cause major or fatal bleeding. Monitor INR regularly in every treated patient; drugs, dietary changes and other factors alter anticoagulation. Educate patients about preventing and recognizing bleeding.

Fatal and nonfatal hemorrhage from any organ is the principal adverse reaction. Other reports include allergic/anaphylactic reactions, skin reactions or hair loss, nausea, vomiting, diarrhea, abdominal symptoms, hepatitis/elevated liver enzymes and vasculitis. Serious tissue, renal and embolic complications are described above. Reported events do not provide a universal incidence estimate.

CYP2C9 metabolizes the more potent S-enantiomer; CYP1A2/3A4 contribute to R-enantiomer metabolism. Inhibitors can raise INR and inducers can lower it. Examples include amiodarone, trimethoprim/sulfamethoxazole, metronidazole and azole antifungals increasing effect, and rifampin or carbamazepine reducing effect. Direction and magnitude vary; use more frequent INR testing rather than a fixed percentage adjustment.

Other anticoagulants, aspirin/antiplatelets, NSAIDs and serotonin-reuptake inhibitors can increase bleeding. Combination therapy sometimes has a specific indication, but requires deliberate risk review; do not independently add aspirin or stop a prescribed antiplatelet.

Closely monitor INR when starting/stopping antibiotics or antifungals, even when a predictable CYP interaction is absent. Botanicals vary in composition: garlic/ginkgo may add bleeding risk, while St. John’s wort, ginseng or coenzyme Q10 may reduce effect. Keep vitamin K intake consistent in a balanced diet; do not eliminate all leafy vegetables. Avoid abrupt dietary changes and review alcohol use and supplements with the team.

Warfarin crosses the placenta and can cause embryopathy, fetal bleeding/death, miscarriage and CNS/eye abnormalities. Pregnancy is contraindicated except selected high-thromboembolic-risk mechanical-valve situations where benefit may outweigh harm. Verify pregnancy status before initiation and use effective contraception during treatment and for at least 1 month after the final dose. Pregnancy or plans to conceive require immediate specialist discussion.

Warfarin was not detected in milk in a limited study. Consider maternal need and breastfeeding benefits; monitor the infant for bruising or bleeding. Effects in premature infants were not evaluated in the selected label.

Adequate controlled pediatric studies and optimal dosing are not established; pediatric use relies on limited data and adult recommendations with frequent individualized INR assessment. Nutrition/formula vitamin K and age influence response. Older adults may have greater sensitivity and need lower doses and closer bleeding surveillance; avoid traumatic activities and address adherence/fall risks.

The label specifies no calculated renal dose adjustment, but recommends more frequent INR monitoring. Kidney disease increases bleeding/anticoagulant-related kidney-injury vulnerability. Hepatic dysfunction can increase response through reduced factor synthesis and metabolism; intensify monitoring for bleeding and INR changes.

Warfarin inhibits vitamin K regeneration through the VKORC1-associated reductase system, reducing functional factors II, VII, IX and X and proteins C/S. It prevents further thrombus growth rather than directly lysing a clot.

An anticoagulant effect can begin within 24 hours, with peak effect delayed 72–96 hours; a single dose’s effect may persist 2–5 days. Oral absorption is essentially complete, protein binding about 99%, and hepatic metabolism predominates. Effective half-life averages about 40 hours (range 20–60), distinct from the longer terminal phase. Very little unchanged warfarin is excreted in urine.

S-warfarin is more potent and chiefly metabolized by CYP2C9. CYP2C9/VKORC1 variation, age, organ disease, interacting drugs and nutrition change dose needs. Genotype-informed estimates are not interchangeable with a stable therapeutic INR or a universal maintenance dose.

Document indication, INR target, planned duration and actual daily schedule. Monitor INR and signs of bleeding/thrombosis; assess blood count, renal/hepatic status and medication/diet changes as clinically indicated. Reassess extended treatment periodically. Increase INR checks after intercurrent illness or changes to drugs, diet or adherence.

Carry anticoagulant identification and tell every clinician/dentist. Maintain consistent vitamin K intake and attend INR appointments. Report red/brown urine, black/bloody stools, prolonged bleeding, skin pain/discoloration or purple/cold toes. Seek urgent care after significant head injury or severe neurologic symptoms. Do not independently stop treatment, alter dose, add OTC medicines or change a procedure plan.

Obtain urgent medical assessment for overdose or major bleeding. Management depends on INR, bleeding and clinical circumstances and may require holding warfarin, vitamin K and urgent factor replacement. This profile supplies no home reversal dose, universal hold algorithm or product-conversion instructions.

Appearance

Peach, round, single-scored tablet

Debossing

WRF / 5 · 832 on reverse

Example package

NDC 0832-1216-00 · bottle of 100

Manufacturer

Upsher-Smith Laboratories LLC

The selected oral tablets contain 1, 2, 2.5, 3, 4, 5, 6, 7.5 or 10 mg warfarin sodium. Each has WRF above the score, strength below and 832 on the reverse. Product-specific colors differ by strength; the selected 10 mg tablet is white and dye-free. Other manufacturers and compounded liquids need their own identification and concentration verification.

Store at 20–25°C, with permitted excursions 15–30°C. Protect from light/moisture and dispense in a tight, light-resistant container with child-resistant closure. Pregnant pharmacy/clinical personnel should avoid exposure to crushed or broken tablets; follow appropriate handling/disposal procedures. Keep away from children.