warfarin and Tuberculosis--Pulmonary

Rifampicin remains one of the first-line drugs used in tuberculosis therapy. This drug's potential to induce the hepatic cytochrome P450 oxidative enzyme system increases the risk of drug-drug interactions. Thus, although the presence of comorbidities typically necessitates the use of multiple drugs, the co-administration of rifampicin and warfarin may lead to adverse drug events. We report a bleeding episode after termination of the co-administration of rifampicin and warfarin and detail the challenges related to international normalized ratio (INR) monitoring.. A 59-year-old Brazilian woman chronically treated with warfarin for atrial fibrillation (therapeutic INR range: 2.0-3.0) was referred to a multidisciplinary anticoagulation clinic at a university hospital. She showed anticoagulation resistance at the beginning of rifampicin therapy, as demonstrated by repeated subtherapeutic INR values. Three months of sequential increases in the warfarin dosage were necessary to reach a therapeutic INR, and frequent visits to the anticoagulation clinic were needed to educate the patient about her pharmacotherapy and to perform the warfarin dosage adjustments. The warfarin dosage also had to be doubled at the beginning of rifampicin therapy. However, four weeks after rifampicin discontinuation, an excessively high INR was observed (7.22), with three-day macroscopic hematuria and the need for an immediate reduction in the warfarin dosage. A therapeutic and stable INR was eventually attained at 50% of the warfarin dosage used by the patient during tuberculosis therapy.. The present case exemplifies the influence of rifampicin therapy on warfarin dosage requirements and the increased risk of bleeding after rifampicin discontinuation. Additionally, this case highlights the need for warfarin weekly monitoring after stopping rifampicin until the maintenance dose of warfarin has decreased to the amount administered before rifampicin use. In particular, patients with cardiovascular diseases and active tuberculosis represent a group with a substantial risk of drug-drug interactions. Learning how to predict and monitor drug-drug interactions may help reduce the incidence of clinically significant adverse drug events.

Topics: Antibiotics, Antitubercular; Anticoagulants; Atrial Fibrillation; Drug Interactions; Female; Hematuria; Humans; Middle Aged; Rifampin; Tuberculosis, Pulmonary; Warfarin

Pulmonary tuberculosis remains an important public health problem globally and one of the most prevalent infectious diseases in Sri Lanka. It can cause a wide variety of complications but hematological manifestations are rare. According to our literature survey, this is the first reported case of the disease associated with deep vein thrombosis in Sri Lanka.. A 37 year old Sri Lankan Sinhalese female presented with fever of one month's duration with productive cough and two weeks painless left lower limb swelling. Chest X-ray showed bilateral inflammatory shadows with a cavitatory lesion on the right apical region. A computed tomographic pulmonary angiography scan excluded pulmonary embolism. She had rising mycoplasma antibody titre (four fold). Acute deep vein thrombosis of the left lower limb was confirmed by venous duplex. Pulmonary tuberculosis was confirmed with positive culture for Mycobacterium tuberculosis. She was treated with clarythromycin, enoxaparin, warfarin and anti tuberculus drugs. It was difficult to maintain her International Normalizing Ratio in the therapeutic range due to drug interactions and poor compliance. At five months of presentation she died of massive pulmonary embolism.. Our case emphasizes that patients with severe pulmonary tuberculosis are at risk of developing thromboembolism and superadded infections. It should be noted that even though starting anti tuberculosis drugs improved haemostatic disturbances, achieving the target International Normalizing Ratio was difficult due to drug interactions. Therefore these patients should be closely followed up to prevent complications and death from pulmonary embolism.

Topics: Adult; Antitubercular Agents; Clarithromycin; Drug Antagonism; Enoxaparin; Fatal Outcome; Female; Humans; Leg; Mycobacterium tuberculosis; Pulmonary Embolism; Treatment Failure; Tuberculosis, Pulmonary; Venous Thrombosis; Warfarin

At the turn of the century, only 300 cases of warfarin-induced skin necrosis (WISN) had been reported. WISN is a rare but potentially fatal complication of warfarin therapy. There are no published reports of WISN occurring in patients with HIV-1 infection or tuberculosis (TB).. We retrospectively reviewed cases of WISN presenting from April 2005 to July 2008 at a referral hospital in Cape Town, South Africa.. Six cases of WISN occurred in 973 patients receiving warfarin therapy for venous thrombosis (0.62%, 95% CI 0.25 - 1.37%). All 6 cases occurred in HIV-1-infected women (median age 30 years, range 27 - 42) with microbiologically confirmed TB and venous thrombosis. All were profoundly immunosuppressed (median CD4+ count at TB diagnosis 49 cells/microl, interquartile range 23 - 170). Of the 3 patients receiving combination antiretroviral therapy, 2 had TB-IRIS (immune reconstitution inflammatory syndrome). The median interval from initiation of antituberculosis treatment to venous thrombosis was 37 days (range 0 - 150). The median duration of parallel heparin and warfarin therapy was 2 days (range 1 - 6). WISN manifested 6 days (range 4 - 8) after initiation of warfarin therapy. The international normalised ratio (INR) at WISN onset was supra-therapeutic, median 6.2 (range 3.8 - 6.6). Sites of WISN included breasts, buttocks and thighs. Four of 6 WISN sites were secondarily infected with drug-resistant nosocomial bacteria (methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter, extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae) 17 - 37 days after WISN onset. In 4 patients, the median interval from WISN onset to death was 43 days (range 25 - 45). One of the 2 patients who survived underwent bilateral mastectomies and extensive skin grafting at a specialist centre.. This is one of the largest case series of WISN. We report a novel clinical entity: WISN in HIV-1 infected patients with TB and venous thrombosis. The occurrence of 6 WISN cases in a 40-month period may be attributed to (i) hypercoagulability, secondary to HIV-1 and TB: (ii) short concurrent heparin and warfarin therapy; and (iii) high loading doses of warfarin. Active prevention and appropriate management of WISN are likely to improve the dire morbidity and mortality of this unusual condition.

Topics: Adult; Anticoagulants; Comorbidity; Female; HIV Infections; Humans; Necrosis; Retrospective Studies; Skin; Tuberculosis; Tuberculosis, Pulmonary; Venous Thrombosis; Warfarin

Rifampin is known to lower plasma warfarin concentrations by increasing the rate of warfarin clearance. We have described a patient in whom an additional potentiating influence on warfarin effect was observed during treatment with rifampin and isoniazid. After cessation of rifampin and isoniazid, prothrombin time was maintained within the same range by a 50% reduction of warfarin doses, despite a twofold rise in the plasma warfarin concentration. This rise in warfarin concentrations can be explained by the known mechanism by which rifampin increases warfarin clearance. After cessation of rifampin, warfarin fractional clearance decreased from 15.2 to 4.2 ml/min; however, the unchanged prothrombin time in the face of the increased warfarin concentration can be explained only by the removal of a potentiating effect that had been present during the coadministration of rifampin and isoniazid. It is likely that rifampin is responsible for this additional potentiating interaction, probably not through a change in warfarin binding, but through a differential effect on warfarin stereoisomer metabolism or through an altered dynamic effect. The role of isoniazid in this interaction cannot be completely ruled out.

Topics: Adult; Drug Administration Schedule; Drug Synergism; Drug Therapy, Combination; Female; Humans; Isoniazid; Lung Diseases, Obstructive; Prothrombin Time; Rifampin; Stimulation, Chemical; Tuberculosis, Pulmonary; Warfarin