129-06-6

Slightly bitter crystalline powder. An anticoagulant used as a rodenticide.

A coumarin derivative, a lactone. Lactones are similar to esters reactive chemistries.

This material is highly toxic orally in humans.

When heated to decomposition, WARFARIN SODIUM emits toxic fumes of sodium oxide.

Colorless solid

Coumadin ,Endo,US,1954

central stimulant

Rodenticide.

About 0.1 mol each of 4-hydroxycoumarin and benzalacetone are dissolved, in any desired order, in about three times their combined weight of pyridine. The solution is refluxed for about 24 hours, and then allowed to cool; after which it is poured into about 15 volumes of water, and acidified to about pH 2 by the addition of hydrochloric acid. An oil separates, and on cooling and standing overnight solidifies. The solid product is recovered, as by filtration, and recrystallized from ethanol, according to US Patent 2,427,578.
The base melts at about 161°C. It is a white crystalline solid, soluble in hot ethyl alcohol and substantially insoluble in cold water; it dissolves in alkali solutions with formation of the salt. The yield is about 40%.
Then, as described in US Patent 2,777,859, warfarin may be reacted with NaOH to give a sodium salt solution. Crystalline warfarin sodium may be prepared as described in US Patent 2,765,321.

Athrombin (Purdue Frederick); Coumadin (Bristol-Myers Squibb); Jantoven (USl); Panwarfin (Abbott).

Anticoagulant

By virtue of its great potency, warfarin sodium at firstwas considered unsafe for use in humans and was used veryeffectively as a rodenticide, especially against rats. At theproper dosage level, however, it can be used in humans, especiallythrough the intravenous route.

In veterinary medicine, warfarin is used primarily for the oral, long-term treatment (or prevention of recurrence) of thrombotic conditions, primarily in cats, dogs, or horses. Use of warfarin in veterinary species is somewhat controversial and due to unproven benefit in reducing mortality, increased expense associated with monitoring, and potential for serious effects (bleeding), many do not recommend its use.

Potentially hazardous interactions with other drugs
There are many significant interactions with warfarin.
Prescribe with care with regard to the following:
Anticoagulant effect enhanced by: alcohol, amiodarone, anabolic steroids, aspirin, aztreonam, bicalutamide, cephalosporins, chloramphenicol, cimetidine, ciprofloxacin, clopidogrel, cranberry juice, danazol, danshen, dipyridamole, dronedarone, disulfiram, entacapone, esomeprazole, exenatide, ezetimibe, fibrates, fluconazole, flutamide, fluvastatin, glucosamine, grapefruit juice, itraconazole, ketoconazole, levamisole, levofloxacin, macrolides, methylphenidate, metronidazole, miconazole, mirtazepine, nalidixic acid, neomycin, norfloxacin, NSAIDs, ofloxacin, omeprazole, pantoprazole, paracetamol, penicillins, proguanil, propafenone, ritonavir, rosuvastatin, saquinavir, SSRIs, simvastatin, sulfinpyrazone, sulphonamides, tamoxifen, tegafur, testosterone, tetracyclines, thyroid hormones, tigecycline, toremifene, tramadol, trimethoprim, valproate, venlafaxine, vitamin E and voriconazole.
Anticoagulant effect decreased by: acitretin, atorvastatin, azathioprine, barbiturates, carbamazepine, enteral feeds, eslicarbazepine, enzalutamide, fosphenytoin, ginseng, griseofulvin, oral contraceptives, phenobarbital, phenytoin, primidone, rifamycins, St John’s wort (avoid concomitant use), sucralfate, vitamin K.
Anticoagulant effects enhanced / reduced by: anion exchange resins, atazanavir, corticosteroids, dietary changes, disopyramide, efavirenz, fosamprenavir, nevirapine, ritonavir, telaprevir, tricyclics, trazodone.
Analgesics: increased risk of bleeding with IV diclofenac and ketorolac - avoid concomitant use.
Anticoagulants: increased risk of haemorrhage with apixaban, dabigatran, edoxaban and rivaroxaban - avoid concomitant use.
Antidiabetic agents: enhanced hypoglycaemic effect with sulphonylureas; also possible changes to anticoagulant effect.
Camomile: enhanced anticoagulation.
Ciclosporin: there have been a few reports of altered anticoagulant effect; decreased ciclosporin levels have been seen rarely.
Cytotoxics: increased risk of bleeding with erlotinib, imatinib and regorafenib; enhanced effect with capecitabine, etoposide, fluorouracil, ifosfamide, gefitinib, gemcitabine, sorafenib and vemurafenib; reduced effect with mercaptopurine and mitotane.
Melatonin: possibly enhanced INR.

The R- and S-isomers are both metabolised in the liver. The S-isomer is metabolised more rapidly than the R-isomer, mainly by the cytochrome P450 isoenzyme CYP2C9, which shows genetic polymorphism. Other isoenzymes are also involved in the metabolism of the R-isomer.
The metabolites, which have negligible or no anticoagulant activity, are excreted in the urine following reabsorption from the bile. Dose in renal impairment G