Prothrombin complex concentrate for reversal of vitamin K antagonist treatment in bleeding and non-bleeding patients
- PMID: 26151108
- PMCID: PMC6516823
- DOI: 10.1002/14651858.CD010555.pub2
Prothrombin complex concentrate for reversal of vitamin K antagonist treatment in bleeding and non-bleeding patients
Abstract
Background: Treatment with vitamin K antagonists is associated with increased morbidity and mortality. Reversal therapy with prothrombin complex concentrate (PCC) is used increasingly and is recommended in the treatment of patients with bleeding complications undertaking surgical interventions, as well as patients at high risk of bleeding. Evidence is lacking regarding indication, dosing, efficacy and safety.
Objectives: We assessed the benefits and harms of PCC compared with fresh frozen plasma in the acute medical and surgical setting involving vitamin K antagonist-treated bleeding and non-bleeding patients. We investigated various outcomes and predefined subgroups and performed sensitivity analysis. We examined risks of bias and applied trial sequential analyses (TSA) to examine the level of evidence, and we prepared a 'Risk of bias' table to test the quality of the evidence.
Search methods: We searched the following databases from inception to 1 May 2013: Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE (Ovid SP); EMBASE (Ovid SP); International Web of Science; Latin American and Caribbean Health Sciences Literature (LILACS) (via BIREME); the Chinese Biomedical Literature Database; advanced Google and the Cumulative Index to Nursing and Allied Health Literature (CINAHL). We applied a systematic and sensitive search strategy to identify relevant randomized clinical trials and imposed no language or date restrictions. We adapted our MEDLINE search strategy for searches in all other databases. We reran the search in October 2014 and found one potential new study of interest. We added this study to a list of 'Studies awaiting classification', and we will incorporate this study into the formal review findings at the time of the review update.
Selection criteria: We included randomized controlled trials (RCTs), irrespective of publication status, date of publication, blinding status, outcomes published or language. We contacted investigators and study authors to request relevant data.
Data collection and analysis: Three review authors independently abstracted data and resolved disagreements by discussion. Our primary outcome measures were 'overall mortality longest follow-up' and 'overall 28-day mortality'. We performed subgroup analyses to assess the effects of PCC in adults in terms of various clinical and physiological outcomes. We presented pooled estimates of the effects of interventions on dichotomous outcomes as risk ratios (RRs), and on continuous outcomes as mean differences (MDs), with 95% confidence intervals (CIs). We assessed risk of bias by assessing trial methodological components and risk of random error through TSA.
Main results: We included four RCTs with a total of 453 participants and determined that none of these trials had overall low risk of bias. We found six ongoing trials from which we were unable to retrieve further data. Three trials provided data on mortality. Meta-analysis showed no statistical effect on overall mortality (RR 0.93, 95% CI 0.37 to 2.33; very low quality of evidence). We were unable to associate use of PCC with the number of complications probably related to the intervention (RR 0.92, 95% CI 0.78 to 1.09; very low quality of evidence). Lack of transfusion data and apparent differences in study design prevented review authors from finding a beneficial effect of PCC in reducing the volume of fresh frozen plasma (FFP) transfused to reverse the effect of vitamin K antagonist treatment. The number of new occurrences of transfusion of red blood cells (RBCs) did not seem to be associated with the use of PCC (RR 1.08, 95% CI 0.82 to 1.43; very low quality of evidence). Still, the included studies demonstrate the possibility of equally reversing vitamin K-induced coagulopathy using PCC without the need for transfusion of FFP. No effect on other predefined outcomes was observed.
Authors' conclusions: In the four included RCTs, use of prothrombin complex concentrate does not appear to reduce mortality or transfusion requirements but demonstrates the possibility of reversing vitamin K-induced coagulopathy without the need for transfusion of fresh frozen plasma. All included trials have high risk of bias and are underpowered to detect mortality, benefit or harm. Clinical and statistical heterogeneity is high, and definitions of clinically important outcomes such as adverse events are highly dissimilar between trials. Only weak observational evidence currently supports the use of PCC in vitamin K antagonist-treated bleeding and non-bleeding patients, and the current systematic review of RCTs does not support the routine use of PCC over FFP. Additional high-quality research is urgently needed.
Conflict of interest statement
Mathias Johansen: no conflicts of interest.
Anne Wikkelsø: no conflicts of interest.
Jens Lunde: no conflicts of interest.
Jørn Wetterslev: I am a member of the Copenhagen Trial Unit Task Force, which develops trial sequential analysis theory and software.
Arash Afshari: no conflicts of interest.
Figures
![1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG01.gif)
![2](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG02.gif)
![3](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG03.gif)
![4](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG04.gif)
![5](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG05.gif)
![6](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG06.gif)
![7](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG07.gif)
![8](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-AFig-FIG08.gif)
![1.1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-CMP-001-01.gif)
![2.1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-CMP-002-01.gif)
![2.2](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-CMP-002-02.gif)
![3.1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-CMP-003-01.gif)
![4.1](https://cdn.statically.io/img/www.ncbi.nlm.nih.gov/pmc/articles/instance/6516823/bin/nCD010555-CMP-004-01.gif)
Update of
- doi: 10.1002/14651858.CD010555
Similar articles
-
Folic acid supplementation and malaria susceptibility and severity among people taking antifolate antimalarial drugs in endemic areas.Cochrane Database Syst Rev. 2022 Feb 1;2(2022):CD014217. doi: 10.1002/14651858.CD014217. Cochrane Database Syst Rev. 2022. PMID: 36321557 Free PMC article.
-
Prophylactic plasma transfusion for patients without inherited bleeding disorders or anticoagulant use undergoing non-cardiac surgery or invasive procedures.Cochrane Database Syst Rev. 2019 Nov 28;11(11):CD012745. doi: 10.1002/14651858.CD012745.pub2. Cochrane Database Syst Rev. 2019. PMID: 31778223 Free PMC article.
-
Pro-coagulant haemostatic factors for the prevention and treatment of bleeding in people without haemophilia.Cochrane Database Syst Rev. 2018 Dec 24;12(12):CD010649. doi: 10.1002/14651858.CD010649.pub2. Cochrane Database Syst Rev. 2018. PMID: 30582172 Free PMC article.
-
Thromboelastography (TEG) or thromboelastometry (ROTEM) to monitor haemostatic treatment versus usual care in adults or children with bleeding.Cochrane Database Syst Rev. 2016 Aug 22;2016(8):CD007871. doi: 10.1002/14651858.CD007871.pub3. Cochrane Database Syst Rev. 2016. PMID: 27552162 Free PMC article. Review.
-
Fibrinogen concentrate in bleeding patients.Cochrane Database Syst Rev. 2013 Aug 29;2013(8):CD008864. doi: 10.1002/14651858.CD008864.pub2. Cochrane Database Syst Rev. 2013. PMID: 23986527 Free PMC article. Review.
Cited by
-
The 2023 WSES guidelines on the management of trauma in elderly and frail patients.World J Emerg Surg. 2024 May 31;19(1):18. doi: 10.1186/s13017-024-00537-8. World J Emerg Surg. 2024. PMID: 38816766 Free PMC article. Review.
-
Four-factor Prothrombin Complex Concentrate During Liver Transplantation: A Retrospective Cohort Study.Transplant Direct. 2024 May 16;10(6):e1637. doi: 10.1097/TXD.0000000000001637. eCollection 2024 Jun. Transplant Direct. 2024. PMID: 38769975 Free PMC article.
-
Efficacy of human prothrombin complex concentrate in the treatment of warfarin overdose in patients receiving warfarin for mechanical heart valve replacement.Medicine (Baltimore). 2024 May 10;103(19):e38022. doi: 10.1097/MD.0000000000038022. Medicine (Baltimore). 2024. PMID: 38728459 Free PMC article.
-
Haemostatic therapies for stroke due to acute, spontaneous intracerebral haemorrhage.Cochrane Database Syst Rev. 2023 Oct 23;10(10):CD005951. doi: 10.1002/14651858.CD005951.pub5. Cochrane Database Syst Rev. 2023. PMID: 37870112 Review.
-
Thromboembolism after treatment with 4-factor prothrombin complex concentrate or plasma for warfarin-related bleeding.J Thromb Thrombolysis. 2022 Oct;54(3):470-479. doi: 10.1007/s11239-022-02695-5. Epub 2022 Aug 19. J Thromb Thrombolysis. 2022. PMID: 35984591 Free PMC article.
References
References to studies included in this review
Boulis 1999 {published data only}
-
- Boulis NM, Bobek MP, Schmaier A, Hoff JT. Use of factor IX complex in warfarin‐related intracranial hemorrhage. Neurosurgery 1999;45(5):1113‐8; (discussion 1118‐9). [MEDLINE: ] - PubMed
Demeyere 2010 {published data only}
-
- Demeyere R, Gillardin S, Arnout J, Strengers PF. Comparison of fresh frozen plasma and prothrombin complex concentrate for the reversal of oral anticoagulants in patients undergoing cardiopulmonary bypass surgery: a randomized study. Vox Sanguinis 2010;99(3):251‐60. [MEDLINE: ] - PubMed
Majeed 2013 {published and unpublished data}
-
- Majed AR, Goldstein JN, Milling TJ, Lewis B, Goldberg‐Alberts R, Hug BA, et al. Randomized phase IIIb study of rapid vitamin K antagonist reversal in patients requiring an urgent surgical procedure: four‐factor prothrombin complex concentrate is superior to plasma. Blood 2013;122(21):3588.
Sarode 2013 {published data only}
-
- Sarode R, Milling TJ Jr, Refaai MA, Mangione A, Schneider A, Durn BL, et al. Efficacy and safety of a 4‐factor prothrombin complex concentrate in patients on vitamin K antagonists presenting with major bleeding: a randomized, plasma‐controlled, phase IIIb study. Circulation 2013;128(11):1234‐43. [MEDLINE: ] - PMC - PubMed
References to studies excluded from this review
Aart 2006 {published data only}
-
- Aart LV, Eijkhout HW, Kamphuis JS, Dam M, Schattenkerk ME, Schouten JT, et al. Individualized dosing regimen for prothrombin complex concentrate more effective than standard treatment in the reversal of oral anticoagulant therapy: an open, prospective randomized controlled trial. Thrombosis Research 2006;118:313‐20. - PubMed
Eerenberg 2011 {published data only}
-
- Eerenberg ES, Kamphuisen PW, Sijpkens MK, Meijers JC, Buller HR, Levi M. Reversal of rivaroxaban and dabigatran by prothrombin complex concentrate. Circulation 2011;124:1573‐9. - PubMed
Marlu 2012 {published data only}
-
- Raphael M, Enkelejda H, Adeline P, Albaladejo P, Crackowski JL, Pernod G. Effect of non‐specific reversal agents on anticoagulant activity of dabigatran and rivaroxaban. Thrombosis and Haemostasis 2012;108:217‐24. - PubMed
References to studies awaiting assessment
References to ongoing studies
Ahonen 2013 {published and unpublished data}
-
- Use of Prothrombin Complex Concentrate and Fibrinogen Compared With Fresh Frozen Plasma in the Treatment of Postpartum Haemorrhage. Ongoing study July 2013.
Frenzel 2008 {published and unpublished data}
-
- A Randomized, Open‐Label, Efficacy and Safety Study of OCTAPLEX and Fresh Frozen Plasma in Patients Under Vitamin K Antagonist Therapy With the Need for Urgent Surgery or Invasive Procedures. Ongoing study April 2008.
Innerhofer 2012 {published and unpublished data}
-
- RETIC trial: Reversal of Trauma Induced Coagulopathy Using Coagulation Factor Concentrates or Fresh Frozen Plasma. Ongoing study March 2012. - PubMed
Ranucci 2011 {published and unpublished data}
-
- The ZEro PLASma Trial (ZEPLAST): Avoidance of Fresh Frozen Plasma in Cardiac Surgery. Ongoing study November 2011.
Roy 2013 {published and unpublished data}
-
- PREVACT: Preventive REversal of Vitamine K Antagonist in Minor Craniocerebral Trauma. Ongoing study October 2013.
Steiner 2009 {published and unpublished data}
-
- Multi‐centre, Prospective, Randomized Trial on the Use of Prothrombin Complex and Fresh Frozen Plasma in Patients With Intracerebral Hemorrhage Related to Vitamin K Antagonists. Ongoing study July 2009.
Additional references
Ansell 2008
-
- Ansell J, Hirsh J, Hylek E, Jacobson A, Crowther M, Palareti G, American College of Chest Physicians. Pharmacology and Management of the Vitamin K Antagonists: American College of Chest Physicians Evidence‐Based Clinical Practice Guidelines (8th Edition). Chest 2008;133(6 Suppl):160S‐98S. [MEDLINE: ] - PubMed
Baglin 2006
-
- Baglin TP, Keeling DM, Watson HG. Guidelines on Oral Anticoagulation (Warfarin): Third Edition‐‐2005 Update. British Journal of Haematology 2006;132(3):277‐85. [MEDLINE: ] - PubMed
Brok 2009
-
- Brok J, Thorlund K, Wetterslev J, Gluud C. Apparently conclusive meta‐analyses may be inconclusive—Trial sequential analysis adjustment of random error risk due to repetitive testing of accumulating data in apparently conclusive neonatal meta‐analyses. International Journal of Epidemiology 2009;38(1):287‐98. [MEDLINE: ] - PubMed
Bruce 2008
Cartmill 2000
-
- Cartmill M, Dolan G, Byrne JL, Byrne PO. Prothrombin complex concentrate for oral anticoagulant reversal in neurosurgical emergencies. British Journal of Neurosurgery 2000;5:458‐61. [MEDLINE: ] - PubMed
Chan 2004
-
- Chan AW, Hróbjartsson A, Haahr MT, Gøtzsche PC, Altman DG. Empirical evidence for selective reporting of outcomes in randomized trials: comparison of protocols to published articles. JAMA 2004;291(20):2457‐65. [MEDLINE: ] - PubMed
Dentali 2011
-
- Dentali F1, Marchesi C, Pierfranceschi MG, Crowther M, Garcia D, Hylek E, et al. Safety of prothrombin complex concentrates for rapid anticoagulation reversal of vitamin K antagonists. A meta‐analysis. Thrombosis and Haemostasis 2011;106(3):429‐38. [MEDLINE: ] - PubMed
Franchini 2010
GradePro [Computer program]
-
- GradePro Working Team. GRADEPro. 3.2 for Windows. http://ims.cochrane.org/revman/other–resources/gradepro/download, 2008.
Guyatt 2008
Higgins 2003
Higgins 2011
-
- Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. www.cochrane‐handbook.org.
Holland 2006
-
- Holland LL, Brooks JP. Toward rational fresh frozen plasma transfusion: the effect of plasma transfusion on coagulation test results. American Society of Clinical Pathologists 2006;126(1):133‐9. [MEDLINE: ] - PubMed
Huttner 2006
-
- Huttner HB, Schellinger PD, Hartmann M, Köhrmann M, Juettler E, Wikner J, et al. Hematoma growth and outcome in treated neurocritical care patients with intracerebral hemorrhage related to oral anticoagulant therapy: comparison of acute treatment strategies using vitamin K, fresh frozen plasma, and prothrombin complex concentrates. Stroke 2006;6:1465‐70. [MEDLINE: ] - PubMed
Hutton 2000
-
- Hutton JL, Williamson PR. Bias in meta‐analysis due to outcome variable selection within studies. Journal of the Royal Statistical Society Series C 2000;49:359‐70. [MEDLINE: ]
Koch 2006a
-
- Koch CG, Li L, Duncan AI, Mihaljevic T, Cosgrove DM, Loop FD, et al. Morbidity and mortality risk associated with red blood cell and blood‐component transfusion in isolated coronary artery bypass grafting. Critical Care Medicine 2006;34:1608‐16. [MEDLINE: ] - PubMed
Koch 2006b
-
- Koch CG, Li L, Duncan AI, Mihaljevic T, Loop FD, Starr NJ, et al. Transfusion in coronary artery bypass grafting is associated with reduced long‐term survival. The Annals of Thoracic Surgery 2006;81(5):1650‐7. [MEDLINE: ] - PubMed
Kor 2010
-
- Kor DJ, Stubbs JR, Gajic O. Perioperative coagulation management—fresh frozen plasma. Best Practice & Research. Clinical Anaesthesiology 2010;24(1):51‐64. [MEDLINE: ] - PubMed
Lan 1983
-
- Lan KKG, DeMets DL. Discrete sequential boundaries for clinical trials. Biometrika 1983;70:659‐63.
Leissinger 2008
-
- Leissinger CA, Blatt PM, Hoots WK, Ewenstein B. Role of prothrombin complex concentrates in reversing warfarin anticoagulation: a review of the literature. American Journal of Hematology 2008;83:137‐43. [MEDLINE: ] - PubMed
Levi 2009
-
- Levi M. Emergency reversal of antithrombotic treatment. Internal and Emergency Medicine 2009;4(2):137‐45. [MEDLINE: ] - PubMed
Levy 2008
-
- Levy JH, Tanaka KA, Dietrich W. Perioperative hemostatic management of patients treated with vitamin K antagonists. Anesthesiology 2008;109(5):918‐26. [MEDLINE: ] - PubMed
Lin 2013
-
- Lin DM, Murphy LS, Tran M. Use of prothrombin complex concentrates and fibrinogen concentrates in the perioperative setting: a systematic review. Transfusion Medicine Reviews 2013;27:91‐104. [MEDLINE: ] - PubMed
Makris 1997
-
- Makris M, Greaves M, Phillips WS, Kitchen S, Rosendaal FR, Preston EF. Emergency oral anticoagulant reversal: the relative efficacy of infusions of fresh frozen plasma and clotting factor concentrate on correction of the coagulopathy. Thrombosis Haemostasis 1997;3:477‐80. [MEDLINE: ] - PubMed
Ostermann 2007
-
- Ostermann H, Haertel S, Knaub S, Kalina U, Jung K, Pabinger I. Pharmacokinetics of beriplex P/N prothrombin complex concentrate in healthy volunteers. Thrombosis and Haemostasis 2007;98(4):790‐7. [MEDLINE: ] - PubMed
Ozgonenel 2007
-
- Ozgonenel B, O'Malley B, Krishen P, Eisenbrey AB. Warfarin reversal emerging as the major indication for fresh frozen plasma use at a tertiary care hospital. American Journal of Hematology 2007;82(12):1091‐4. [MEDLINE: ] - PubMed
Palareti 1996
-
- Palareti G, Leali N, Coccheri S, Poggi M, Manotti C, D'Angelo A, et al. Bleeding complications of oral anticoagulant treatment: an inception‐cohort, prospective collaborative study (ISCOAT). Italian Study on Complications of Oral Antcoagulant Therapy. Lancet 1996;348(9025):423‐8. [MEDLINE: ] - PubMed
Pindur 1999
-
- Pindur G, Mörsdorf S. The use of prothrombin complex concentrates in the treatment of hemorrhages induced by oral anticoagulation. Thrombosis Research 1999;95(4 Suppl 1):S57‐61. [MEDLINE: ] - PubMed
Pogue 1997
-
- Pogue JM, Yusuf S. Cumulating evidence from randomized trials: utilizing sequential monitoring boundaries for cumulative meta‐analysis. Controlled Clinical Trials 1997;18(6):580‐93. [MEDLINE: ] - PubMed
Pogue 1998
-
- Pogue JM, Yusuf S. Overcoming the limitations of current meta‐analysis of randomised controlled trials. Lancet 1998;351(9095):47‐52. [MEDLINE: ] - PubMed
RevMan 5.3 [Computer program]
-
- The Nordic Cochrane Centre, The Cochrane Collaboration 2014. Review Manager (RevMan) [Computer program]. Version 5.3. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration 2014, 2013.
Riess 2007
-
- Riess HB, Meier‐Hellmann A, Motsch J, Elias M, Kursten FW, Dempfle CE. Prothrombin complex concentrate (Octaplex) in patients requiring immediate reversal of oral anticoagulation. Thrombosis Research 2007;121(2):9‐16. [MEDLINE: ] - PubMed
Schick 2009
Steiner 2011
-
- Steiner T, Freiberger A, Griebe M, Hüsing J, Ivandic B, Kollmar R, et al. International normalised ratio normalisation in patients with coumarin‐related intracranial haemorrhages—the INCH trial: a randomised controlled multicentre trial to compare safety and preliminary efficacy of fresh frozen plasma and prothrombin complex—study design and protocol. International Journal of Stroke 2011;6(3):271‐7. [MEDLINE: ] - PubMed
Sutton 2002
-
- Sutton AJ, Cooper NJ, Lambert PC, Jones DR, Abrams KR, Sweeting MJ. Meta‐analysis of rare and adverse event data. Expert Review of Pharmacoeconomics & Outcomes Research 2002;2(4):367‐79. [MEDLINE: ] - PubMed
Sørensen 2011
Theusinger 2009
-
- Theusinger OM, Spahn DR, Ganter MT. Transfusion in trauma: why and how should we change our current practice?. Current Opinion Anaesthesiology 2009;22(2):305‐12. [MEDLINE: ] - PubMed
Thorlund 2009
-
- Thorlund K, Devereaux PJ, Wetterslev J, Guyatt G, Ioannidis JP, Thabane L, et al. Can trial sequential monitoring boundaries reduce spurious inferences from meta‐analyses?. International Journal of Epidemiology 2009;38(1):276‐86. [MEDLINE: ] - PubMed
Van Aart 2006
-
- Aart L, Eijkhout HW, Kamphuis JS, Dam M, Schattenkerk ME, Schouten TJ, et al. Individualized dosing regimen for prothrombin complex concentrate more effective than standard treatment in the reversal of oral anticoagulant therapy: an open, prospective randomized controlled trial. Thrombosis Research 2006;118(3):313‐20. [MEDLINE: ] - PubMed
Vang 2011
-
- Vang ML, Hvas AM, Ravn HB. Urgent reversal of vitamin K antagonist therapy. Acta Anaesthesiologica Scandinavica 2011;55(5):507‐16. [MEDLINE: ] - PubMed
Vigué 2009
Warren 2009
-
- Warren O, Simon B. Massive, fatal, intracardiac thrombosis associated with prothrombin complex concentrate. Annals of Emergency Medicine 2009;53(6):758‐61. [MEDLINE: ] - PubMed
Wetterslev 2008
-
- Wetterslev J, Thorlund K, Brok J, Gluud C. Trial sequential analysis may establish when firm evidence is reached in cumulative meta‐analysis. Journal of Clinical Epidemiology 2008;61(1):64‐75. [MEDLINE: ] - PubMed
References to other published versions of this review
Johansen 2013
-
- Johansen M, Wikkelsø A, Lunde J, Wetterslev J, Afshari A. Prothrombin complex concentrate for perioperative reversal of vitamin K antagonist treatment in bleeding and non‐bleeding patients requiring acute surgical intervention. Cochrane Database of Systematic Reviews 2013, Issue 6. [DOI: 10.1002/14651858.CD010555] - DOI - PMC - PubMed
Publication types
MeSH terms
Substances
LinkOut - more resources
Full Text Sources
Medical
Research Materials
Miscellaneous