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International Normalized Ratio (INR) Increases amongst Two Patients Living with HIV on Warfarin after Being Switched from a Nevirapine to a Dolutegravir-Based Antiretroviral Regimen. Case Rep Infect Dis 2021; 2021:9384663. [PMID: 34745671 PMCID: PMC8570848 DOI: 10.1155/2021/9384663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 10/21/2021] [Indexed: 11/17/2022] Open
Abstract
The increased use of dolutegravir-based regimens in the treatment of HIV is unmasking drug interactions, particularly in patients who were previously on nevirapine. Nevirapine is an enzyme inducer and increases the dosing requirements for cytochrome P450 enzyme substrates including warfarin. Upon discontinuing nevirapine, close monitoring of drugs with narrow therapeutic indices is paramount since dosing requirements may significantly reduce, increasing the probability of toxicity development. We present two cases describing interactions experienced by patients living with HIV, while transitioning from nevirapine to dolutegravir-based HIV regimens. The first case describes a 70-year-old man living with HIV and diabetes, while the second case describes a 60-year-old woman living with HIV. They were diagnosed with unprovoked deep vein thrombi, and while receiving treatment with warfarin, their HIV medication regimen was changed from lamivudine, zidovudine, nevirapine, and septrin to lamivudine, tenofovir, dolutegravir, and septrin. During the weeks following this switch, warfarin requirements decreased resulting in supratherapeutic INRs. With the continued promotion of dolutegravir-based HIV regimens as the preferred option for the treatment of HIV in President's Emergency Plan for AIDS Relief (PEPFAR) supported HIV treatment programs in Africa, clinicians must be aware of the potentially life-threatening consequences of switching antiretroviral regimens. It is hoped that a greater awareness of this potential side effect could lead to increased monitoring and prevention of the consequences of drug interactions.
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Cattaneo D, Bernacchia D, Beltrami M, Resnati C, Meraviglia P, Gervasoni C. When the absence of an interaction can become clinically relevant. AIDS 2021; 35:1327-1328. [PMID: 34076620 DOI: 10.1097/qad.0000000000002878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Dario Cattaneo
- Gestione Ambulatoriale Politerapie (GAP) Outpatient Clinic
- Unit of Clinical Pharmacology
| | - Dario Bernacchia
- Department of Infectious Diseases, ASST Fatebenefratelli Sacco University Hospital, Milan, Italy
| | - Martina Beltrami
- Department of Infectious Diseases, ASST Fatebenefratelli Sacco University Hospital, Milan, Italy
| | | | - Paola Meraviglia
- Department of Infectious Diseases, ASST Fatebenefratelli Sacco University Hospital, Milan, Italy
| | - Cristina Gervasoni
- Gestione Ambulatoriale Politerapie (GAP) Outpatient Clinic
- Department of Infectious Diseases, ASST Fatebenefratelli Sacco University Hospital, Milan, Italy
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Vizcarra P, Guillemi S, Eyawo O, Hogg RS, Montaner JS, Bennett M. Stroke and Systemic Thromboembolism Prevention in People Living With Human Immunodeficiency Virus With Atrial Fibrillation: A Review of Its Implications for Clinical Practice. CJC Open 2019; 1:245-255. [PMID: 32159116 PMCID: PMC7063632 DOI: 10.1016/j.cjco.2019.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Accepted: 06/09/2019] [Indexed: 11/17/2022] Open
Abstract
In the last few decades, types of diseases affecting people living with human immunodeficiency virus (PLHIV) have shifted as the population ages, with cardiovascular disease becoming a leading cause of death in this population. Atrial fibrillation (AF) is an increasingly common arrhythmia both in the general population and in PLHIV, with an estimated prevalence of 2% to 3% among PLHIV. Prevention of stroke and systemic thromboembolism (SSE) with antithrombotic therapy is a cornerstone of AF treatment and substantially decreases AF-related morbidity and mortality. Although updated guidelines extensively discuss this issue, they do not address the peculiarities of PLHIV. The role of human immunodeficiency virus (HIV) infection as an independent factor for SSE in individuals with AF and whether the presence of HIV should alter the threshold for SSE thromboprophylaxis are unknown. Nevertheless, a growing body of evidence describes the increasing burden of comorbidities such as hypertension and stroke in PLHIV, which predispose them to AF and SSE. In the absence of HIV-specific AF guidelines, PLHIV with AF should be comprehensively assessed for their risk of SSE and bleeding using commonly available scores despite them having been primarily validated in the non-HIV population. Both vitamin K antagonists and direct oral anticoagulants can be used in PLHIV. Addressing HIV-related comorbidities and potential drug-drug interactions with antiretrovirals is crucial to prevent SSE and reduce adverse reactions of oral anticoagulants. This review summarizes the current guidelines for SSE prevention in patients with AF and describes key considerations for their implementation among PLHIV receiving antiretroviral therapy.
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Affiliation(s)
- Pilar Vizcarra
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
- Department of Infectious Disease, Hospital “Gral. José de San Martín,” La Plata, Buenos Aires, Argentina
| | - Silvia Guillemi
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
- Department of Family Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Oghenowede Eyawo
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
- Faculty of Health, York University, Toronto, Ontario, Canada
| | - Robert S. Hogg
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
| | - Julio S. Montaner
- British Columbia Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada
- Division of AIDS, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Matthew Bennett
- Vancouver Coastal Health, Vancouver, British Columbia, Canada
- Division of Cardiology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Chary A, Nguyen NN, Maiton K, Holodniy M. A review of drug-drug interactions in older HIV-infected patients. Expert Rev Clin Pharmacol 2017; 10:1329-1352. [PMID: 28922979 DOI: 10.1080/17512433.2017.1377610] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
INTRODUCTION The number of older HIV-infected people is growing due to increasing life expectancies resulting from the use of antiretroviral therapy (ART). Both HIV and aging increase the risk of other comorbidities, such as cardiovascular disease, osteoporosis, and some malignancies, leading to greater challenges in managing HIV with other conditions. This results in complex medication regimens with the potential for significant drug-drug interactions and increased morbidity and mortality. Area covered: We review the metabolic pathways of ART and other medications used to treat medical co-morbidities, highlight potential areas of concern for drug-drug interactions, and where feasible, suggest alternative approaches for treating these conditions as suggested from national guidelines or articles published in the English language. Expert commentary: There is limited evidence-based data on ART drug interactions, pharmacokinetics and pharmacodynamics in the older HIV-infected population. Choosing and maintaining effective ART regimens for older adults requires consideration of side effect profile, individual comorbidities, interactions with concurrent prescriptions and non-prescription medications and supplements, dietary patterns with respect to dosing, pill burden and ease of dosing, cost and affordability, patient preferences, social situation, and ART resistance history. Practitioners must remain vigilant for potential drug interactions and intervene when there is a potential for harm.
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Affiliation(s)
- Aarthi Chary
- a Department of Medicine , Veterans Affairs Palo Alto Health Care System , Palo Alto , CA , USA.,b Division of Infectious Diseases and Geographic Medicine , Stanford University School of Medicine , Stanford , CA , USA
| | - Nancy N Nguyen
- c Department of Pharmacy , Veterans Affairs Palo Alto Health Care System , Palo Alto , CA , USA.,d Department of Pharmacy Practice, Thomas J. Long School of Pharmacy & Health Sciences , University of the Pacific , Stockton , CA , USA
| | - Kimberly Maiton
- d Department of Pharmacy Practice, Thomas J. Long School of Pharmacy & Health Sciences , University of the Pacific , Stockton , CA , USA
| | - Mark Holodniy
- a Department of Medicine , Veterans Affairs Palo Alto Health Care System , Palo Alto , CA , USA.,b Division of Infectious Diseases and Geographic Medicine , Stanford University School of Medicine , Stanford , CA , USA.,e Office of Public Health Surveillance & Research , Veterans Affairs Palo Alto Health Care System , Palo Alto , CA , USA
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Jackson BS, Mokoena T. Comparison of the therapeutic dose of warfarin in HIV-infected and HIV-uninfected patients: a study of clinical practice. BMJ Open 2017; 7:e013709. [PMID: 28179414 PMCID: PMC5306524 DOI: 10.1136/bmjopen-2016-013709] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND People infected with HIV are prone to venous thrombosis. Treatment of thrombosis is primarily with warfarin. No studies have addressed the effects of HIV infection on warfarin dose. The aims of this study were to determine whether the therapeutic dose of warfarin and induction time to therapeutic dose in HIV-infected patients differ from that in HIV-uninfected patients. METHODS A prospective and retrospective descriptive study of induction time to therapeutic warfarin dose, as well as of ambulant therapeutic warfarin dose, was performed. HIV-infected and HIV-uninfected patients being treated after deep venous thrombosis with or without pulmonary embolism were compared. Sex and use of antiretroviral drugs (ARVs) were also compared in the groups. RESULTS 234 patients were entered into the study. Induction time to therapeutic warfarin dose did not differ between the 2 groups. The mean therapeutic dose of warfarin was higher in the HIV-infected than the HIV-uninfected group: 6.06 vs 5.72 mg/day, but this was not statistically significant (p=0.29). There was no difference in therapeutic warfarin dose between ARV-naïve groups-HIV-uninfected and HIV-infected patients not on ARVs. CONCLUSIONS There appears to be little effect of HIV infection on warfarin dosing. Warfarin therapy should be administered conventionally in HIV-infected patients.
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Affiliation(s)
- B S Jackson
- Department of Surgery, University of Pretoria and Steve Biko Academic Hospital, Pretoria, South Africa
| | - T Mokoena
- Department of Surgery, University of Pretoria and Steve Biko Academic Hospital, Pretoria, South Africa
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Di Minno A, Frigerio B, Spadarella G, Ravani A, Sansaro D, Amato M, Kitzmiller JP, Pepi M, Tremoli E, Baldassarre D. Old and new oral anticoagulants: Food, herbal medicines and drug interactions. Blood Rev 2017; 31:193-203. [PMID: 28196633 DOI: 10.1016/j.blre.2017.02.001] [Citation(s) in RCA: 134] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 02/02/2017] [Indexed: 12/21/2022]
Abstract
The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.
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Affiliation(s)
| | | | - Gaia Spadarella
- Dipartimento di Medicina Clinica e Chirurgia, Università degli Studi di Napoli "Federico II", Naples, Italy.
| | | | | | - Mauro Amato
- Centro Cardiologico Monzino, IRCCS, Milan, Italy.
| | | | - Mauro Pepi
- Centro Cardiologico Monzino, IRCCS, Milan, Italy.
| | - Elena Tremoli
- Centro Cardiologico Monzino, IRCCS, Milan, Italy; Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
| | - Damiano Baldassarre
- Centro Cardiologico Monzino, IRCCS, Milan, Italy; Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
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Honda H, Gatanaga H, Aoki T, Watanabe K, Yazaki H, Tanuma J, Tsukada K, Honda M, Teruya K, Kikuchi Y, Oka S. Raltegravir can be used safely in HIV-1-infected patients treated with warfarin. Int J STD AIDS 2013; 23:903-4. [PMID: 23258834 DOI: 10.1258/ijsa.2012.012085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Drug co-administration often affects the patient response to warfarin through various mechanisms. We describe here five HIV-1-infected patients on treatment with warfarin in whom the use of raltegravir was associated with a favourable outcome.
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Affiliation(s)
- H Honda
- AIDS Clinical Center, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku Tokyo 162-8655, Japan.
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Nutescu E, Chuatrisorn I, Hellenbart E. Drug and dietary interactions of warfarin and novel oral anticoagulants: an update. J Thromb Thrombolysis 2011; 31:326-43. [PMID: 21359645 DOI: 10.1007/s11239-011-0561-1] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Clinicians and patients around the world have been intrigued by the concept of developing an oral anticoagulant with a broad therapeutic window and few drug and dietary interactions that can be administered at fixed doses with no or minimal monitoring. The recently approved oral direct thrombin inhibitor dabigatran, along with the emerging oral anti-factor Xa inhibitors, rivaroxaban, apixaban, and edoxaban, have been developed to address many of the shortcomings of warfarin therapy. As warfarin is associated with extensive food and drug interactions, there is also a need to consider such interactions with the new oral anticoagulants. While to date few drug and dietary interactions have been reported with the new oral anticoagulants, it is still early in their development and clinical use cycle. Pharmacokinetic and pharmacodynamic profiles will have to be closely accounted for when determining the likelihood of a potential drug interaction prior to therapy initiation. As the list of drugs and supplements that interact with warfarin is continuously expanding, and the knowledge on drug interactions with the novel oral anticoagulants is still in its infancy, clinicians need to be vigilant when initiating any of these agents or when any changes in the patient's medication profile occur and perform a close screening for potential drug and dietary interactions. The objective of this paper is to give an update on drug and dietary interactions with warfarin and the novel oral anticoagulants, dabigatran, rivaroxaban, apixaban, and edoxaban.
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Affiliation(s)
- Edith Nutescu
- Department of Pharmacy Practice and Center for Pharmacoeconomic Research, University of Illinois at Chicago, College of Pharmacy, 833 S. Wood St. MC 886, Rm 164, Chicago, IL 60612, USA.
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Bungard TJ, Yakiwchuk E, Foisy M, Brocklebank C. Drug Interactions Involving Warfarin: Practice Tool and Practical Management Tips. Can Pharm J (Ott) 2011. [DOI: 10.3821/1913-701x-144.1.21] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Tammy J. Bungard
- From the Anticoagulation Management Service and Division of Cardiology, Department of Medicine, University of Alberta (Bungard), Edmonton, Alberta; College of Pharmacy and Nutrition, University of Saskatchewan (Yakiwchuk [student]), Saskatoon, Saskatchewan; Northern Alberta HIV Program, Alberta Health Services (Foisy), Edmonton, Alberta; Anticoagulation Program, Alberta Health Services (Brockle-bank), Calgary, Alberta. Contact
| | - Erin Yakiwchuk
- From the Anticoagulation Management Service and Division of Cardiology, Department of Medicine, University of Alberta (Bungard), Edmonton, Alberta; College of Pharmacy and Nutrition, University of Saskatchewan (Yakiwchuk [student]), Saskatoon, Saskatchewan; Northern Alberta HIV Program, Alberta Health Services (Foisy), Edmonton, Alberta; Anticoagulation Program, Alberta Health Services (Brockle-bank), Calgary, Alberta. Contact
| | - Michelle Foisy
- From the Anticoagulation Management Service and Division of Cardiology, Department of Medicine, University of Alberta (Bungard), Edmonton, Alberta; College of Pharmacy and Nutrition, University of Saskatchewan (Yakiwchuk [student]), Saskatoon, Saskatchewan; Northern Alberta HIV Program, Alberta Health Services (Foisy), Edmonton, Alberta; Anticoagulation Program, Alberta Health Services (Brockle-bank), Calgary, Alberta. Contact
| | - Cynthia Brocklebank
- From the Anticoagulation Management Service and Division of Cardiology, Department of Medicine, University of Alberta (Bungard), Edmonton, Alberta; College of Pharmacy and Nutrition, University of Saskatchewan (Yakiwchuk [student]), Saskatoon, Saskatchewan; Northern Alberta HIV Program, Alberta Health Services (Foisy), Edmonton, Alberta; Anticoagulation Program, Alberta Health Services (Brockle-bank), Calgary, Alberta. Contact
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Abstract
IMPORTANCE OF THE FIELD Antiretroviral therapy exhibits significant potential to alter the metabolism of other medications. Warfarin is widely used for the management of clotting disorders and is prone to drug-drug interactions that can result in subtherapeutic anticoagulation or over-anticoagulation. AREAS COVERED IN THIS REVIEW The mechanism and clinical significance of drug-drug interactions between warfarin and individual antiretrovirals are discussed. Literature searches were conducted in August of 2009 using multiple databases including Medline (1950 - 2009), EMBASE (1980 - 2009), International Pharmaceutical Abstracts (1970 - 2009) and the Cochrane Database of Systematic Reviews. The following search terms were utilized: warfarin, HIV, antiretroviral, drug interaction, protease inhibitor (PI), non-nucleoside reverse-transcriptase inhibitor (NNRTI), cytochrome P450 (CYP450), CYP2C9 and individual antiretrovirals by name. The manufacturers of PIs and NNRTIs were also contacted regarding unpublished data. WHAT THE READER WILL GAIN Clinicians will gain an understanding of the antiretrovirals that are prone to alter warfarin metabolism and the implications for warfarin dose modification. TAKE HOME MESSAGE Metabolic interaction between warfarin and antiretrovirals is likely, particularly if NNRTIs or PIs are included in the antiretroviral regimen. Titration of warfarin dose should be conducted on the basis of close monitoring of the international normalized ratio. Empiric warfarin dose modifications should be considered for individual antiretrovirals.
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Affiliation(s)
- Michelle D Liedtke
- Department of Pharmacy, University of Oklahoma, Health Sciences Center, College of Pharmacy, 1110 N Stonewall, CPB 206, Oklahoma City, OK 73117, USA.
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Inefficacité de l’antivitamine K chez une patiente séropositive pour le virus de l’immunodéficience humaine traitée par névirapine. Presse Med 2009; 38:1696-8. [DOI: 10.1016/j.lpm.2009.03.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 03/04/2009] [Accepted: 03/05/2009] [Indexed: 11/22/2022] Open
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Honda H, Gatanaga H, Matsumura J, Kamimura M, Goto K, Tsukada K, Honda M, Teruya K, Kikuchi Y, Oka S. Favourable use of non-boosted fosamprenavir in patients treated with warfarin. Int J STD AIDS 2009; 20:441. [DOI: 10.1258/ijsa.2009.009108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- H Honda
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - H Gatanaga
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - J Matsumura
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
- Department of Microbiology and Immunology, Nippon Medical School, Tokyo, Japan
| | - M Kamimura
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - K Goto
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
- Department of Infectious Diseases, Graduate School of Medicine, Faculty of Medicine, University of Tokyo, Tokyo, Japan
| | - K Tsukada
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - M Honda
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - K Teruya
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - Y Kikuchi
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
| | - S Oka
- AIDS Clinical Center, International Medical Center of Japan, Tokyo, Japan
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Abstract
OBJECTIVE To review the literature for information regarding interactions between warfarin and antiretroviral agents and evaluate the clinical significance of these interactions. DATA SOURCES Primary literature was identified through a search of MEDLINE (1950-July 2008) and International Pharmaceutical Abstracts (1970-July 2008) using individual antiretroviral drug names and the following key search terms: warfarin, antiretroviral, protease inhibitor, nonnucleoside reverse transcriptase inhibitor, cytochrome P450, 2C9, HIV, and drug interactions. Relevant abstracts from infectious disease and HIV conferences (2005-2008), reference citations from relevant articles, and manufacturers' product information were also reviewed. STUDY SELECTION AND DATA EXTRACTION All English-language articles identified through the data search were examined. Studies and reports addressing warfarin interactions with antiretrovirals, CYP2C9 polymorphism, and antiretroviral CYP2C9 effects were evaluated. A total of 12 case reports were identified that described interactions between warfarin and either protease inhibitors (PIs) or nonnucleoside reverse transcriptase inhibitors (NNRTIs). DATA SYNTHESIS The drugs used in the case reports were limited to 6 antiretroviral agents (efavirenz, nevirapine, lopinavir/ritonavir, nelfinavir, saquinavir, ritonavir). The mechanism of interaction between antiretroviral agents and warfarin appears to be mediated through alteration in CYP2C9 metabolism. Concurrent use of warfarin with efavirenz or saquinavir was associated with overanticoagulation, identified by increases in international normalized ratio (INR). Use of warfarin with lopinavir/ritonavir, nelfinavir, ritonavir, and nevirapine resulted in subtherapeutic INRs. Interactions with delavirdine, etravirine, and atazanavir are anticipated; however, no published cases have reported these interactions. Interactions between warfarin and nucleoside reverse transcriptase inhibitors, integrase inhibitors, fusion inhibitors, and CCR5 antagonists are not anticipated. CONCLUSIONS Interactions between warfarin and antiretrovirals are likely, especially when PIs or NNRTIs are used. Induction or inhibition of warfarin metabolism may occur, depending on the specific antiretroviral agent. When warfarin is used concurrently with antiretrovirals, close monitoring of INR response is recommended in lieu of empiric warfarin dosing adjustments, given the limited information available and the quality of evidence.
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Affiliation(s)
- Michelle D Liedtke
- Department of Pharmacy, College of Pharmacy, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73117, USA.
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Fulco PP, Zingone MM, Higginson RT. Possible antiretroviral therapy-warfarin drug interaction. Pharmacotherapy 2008; 28:945-9. [PMID: 18576910 DOI: 10.1592/phco.28.7.945] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Highly active antiretroviral therapy (HAART) for human immunodeficiency virus (HIV) has resulted in significant morbidity and mortality reductions. Lifelong antiretroviral therapy must be incorporated into each patient's medical regimen. Patients with HIV may also have simultaneous chronic medical conditions, resulting in the possibility of complex drug-drug interactions. We report a possible drug-drug interaction between HAART and warfarin in two patients, as assessed by the Naranjo adverse drug reaction probability scale and the Drug Interaction probability scale. Both patients' pharmacotherapy regimens included a nonnucleoside reverse transcriptase inhibitor (NNRTI), nevirapine, or a protease inhibitor, nelfinavir or lopinavir-ritonavir, and two nucleoside analogs. In both patients, high warfarin doses were required to maintain therapeutic international normalized ratios (INRs). Warfarin has two enantiomers, R-and S-warfarin, which are substrates primarily of cytochrome P450 (CYP) 3A4 (R-warfarin), CYP1A2 (R-warfarin), and CYP2C9 (S-warfarin). Protease inhibitors and NNRTIs have variable effects on CYP: induction, inhibition, or mixed. The increased warfarin doses required in these two patients may have been caused by induction of CYP3A4 by nevirapine, CYP2C9 by nelfinavir, or CYP2C9 by lopinavir-ritonavir. Thus, practitioners should prudently monitor INRs in patients receiving warfarin with concomitant HAART that includes either a protease inhibitor or an NNRTI.
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Affiliation(s)
- Patricia Pecora Fulco
- Department of Pharmacy, Virginia Commonwealth University Medical Center, Richmond, Virginia, USA
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Bonora S, Lanzafame M, D'Avolio A, Trentini L, Lattuada E, Concia E, Di Perri G. Drug Interactions between Warfarin and Efavirenz or Lopinavir-Ritonavir in Clinical Treatment. Clin Infect Dis 2008; 46:146-7. [DOI: 10.1086/524086] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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16
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Walubo A. The role of cytochrome P450 in antiretroviral drug interactions. Expert Opin Drug Metab Toxicol 2007. [DOI: 10.1517/17425255.3.4.583] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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de Maat MMR, Ekhart GC, Huitema ADR, Koks CHW, Mulder JW, Beijnen JH. Drug interactions between antiretroviral drugs and comedicated agents. Clin Pharmacokinet 2003; 42:223-82. [PMID: 12603174 DOI: 10.2165/00003088-200342030-00002] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
HIV-infected individuals usually receive a wide variety of drugs in addition to their antiretroviral drug regimen. Since both non-nucleoside reverse transcriptase inhibitors and protease inhibitors are extensively metabolised by the cytochrome P450 system, there is a considerable potential for pharmacokinetic drug interactions when they are administered concomitantly with other drugs metabolised via the same pathway. In addition, protease inhibitors are substrates as well as inhibitors of the drug transporter P-glycoprotein, which also can result in pharmacokinetic drug interactions. The nucleoside reverse transcriptase inhibitors are predominantly excreted by the renal system and may also give rise to interactions. This review will discuss the pharmacokinetics of the different classes of antiretroviral drugs and the mechanisms by which drug interactions can occur. Furthermore, a literature overview of drug interactions is given, including the following items when available: coadministered agent and dosage, type of study that is performed to study the drug interaction, the subjects involved and, if specified, the type of subjects (healthy volunteers, HIV-infected individuals, sex), antiretroviral drug(s) and dosage, interaction mechanism, the effect and if possible the magnitude of interaction, comments, advice on what to do when the interaction occurs or how to avoid it, and references. This discussion of the different mechanisms of drug interactions, and the accompanying overview of data, will assist in providing optimal care to HIV-infected patients.
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Affiliation(s)
- Monique M R de Maat
- Department of Pharmacy and Pharmacology, Slotervaart Hospital, Amsterdam, The Netherlands.
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Pharmacoepidemiology and drug safety. Pharmacoepidemiol Drug Saf 2001; 10:345-60. [PMID: 11760498 DOI: 10.1002/pds.549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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