title: Making the right choice: optimizing rt-PA and eptifibatide lysis, an in vitro study.
abstract: BACKGROUND
  Recombinant tissue plasminogen activator (rt-PA) is the only FDA approved lytic therapy for acute ischemic stroke. However, there can be complications such as intra-cerebral hemorrhage. This has led to interest in adjuncts such as GP IIb-IIIa inhibitors. However, there is little data on combined therapies. Here, we measure clot lysis for rt-PA and eptifibatide in an in vitro human clot model, and determine the drug concentrations maximizing lysis. A pharmacokinetic model is used to compare drug concentrations expected in clinical trials with those used here. The hypothesis is that there is a range of rt-PA and eptifibatide concentrations that maximize in vitro clot lysis.
  
  
  METHODS
  Whole blood clots were made from blood obtained from 28 volunteers, after appropriate institutional approval. Sample clots were exposed to rt-PA and eptifibatide in human fresh-frozen plasma; rt-PA concentrations were 0, 0.5, 1, and 3.15 μg/ml, and eptifibatide concentrations were 0, 0.63, 1.05, 1.26 and 2.31 μg/ml. All exposures were for 30 minutes at 37 C. Clot width was measured using a microscopic imaging technique and mean fractional clot loss (FCL) at 30 minutes was used to determine lytic efficacy. On average, 28 clots (range: 6-148) from 6 subjects (3-24) were used in each group.
  
  
  CONCLUSIONS
  FCL for control clots was 14% (95% Confidence Interval: 13-15%). FCL was 58% (55-61%) for clots exposed to both drugs at all concentrations, except those at an rt-PA concentration of 3.15 μg/ml, and eptifibatide concentrations of 1.26 μg/ml (Epf) or 2.31 μg/ml. Here, FCL was 43% (36-51) and 35% (32-38) respectively. FCL is maximized at moderate rt-PA and eptifibatide concentration; these values may approximate the average concentrations used in some rt-PA and eptifibatide treatments.
authors.affiliation: Department of Emergency Medicine, University of Cincinnati, USA. shawge@ucmail.uc.edu
authors.forename: George J
authors.initials: GJ
authors.lastname: Shaw
authors.forename: Jason M
authors.initials: JM
authors.lastname: Meunier
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lindsell
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Pancioli
authors.forename: Christy K
authors.initials: CK
authors.lastname: Holland
mesh_terms: D001777:Blood Coagulation / Q000187:drug effects*; D000077542:Eptifibatide; D006801:Humans; D010455:Peptides / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors; D011994:Recombinant Proteins / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*
chemical_list: D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator; D000077542:Eptifibatide
references.citation: Thromb Res. 2006;117(5):603-8
references.pmid: 15951005
references.citation: Ultrasound Med Biol. 2007 Apr;33(4):576-83
references.pmid: 17337113
references.citation: Stroke. 1996 Sep;27(9):1711-8
references.pmid: 8784157
references.citation: Clin Ther. 2004 Mar;26(3):390-8
references.pmid: 15110131
references.citation: Circ Res. 2002 Mar 8;90(4):428-34
references.pmid: 11884372
references.citation: BMC Cardiovasc Disord. 2008 Aug 26;8:19
references.pmid: 18727834
references.citation: Neurosurgery. 2006 Oct;59(4):789-96; discussion 796-7
references.pmid: 16915119
references.citation: Thromb Haemost. 1996 Jan;75(1):127-33
references.pmid: 8713791
references.citation: Thromb Res. 2009;123(3):528-36
references.pmid: 18619651
references.citation: BMC Res Notes. 2009 Jun 30;2:117
references.pmid: 19566947
references.citation: Acoust Res Lett Online. 2005 Jan;6(1):25-29
references.pmid: 18080003
references.citation: CNS Drugs. 2004;18(14):981-8
references.pmid: 15584768
references.citation: Thromb Haemost. 1989 Jun 30;61(3):497-501
references.pmid: 2508258
references.citation: Clin Ther. 2003 Oct;25(10):2564-74
references.pmid: 14667957
references.citation: Am J Cardiol. 2001 Nov 15;88(10):1097-102
references.pmid: 11703951
references.citation: Thromb Res. 1989 Oct 1;56(1):67-75
references.pmid: 2512687
references.citation: N Engl J Med. 2004 Nov 18;351(21):2170-8
references.pmid: 15548777
references.citation: Am J Ophthalmol. 1989 Jul 15;108(1):90-1
references.pmid: 2502019
references.citation: Cerebrovasc Dis. 2005;20(1):18-22
references.pmid: 15925878
references.citation: Circulation. 1997 Feb 18;95(4):846-54
references.pmid: 9054741
references.citation: Circulation. 1996 Sep 1;94(5):1167-74
references.pmid: 8790069
references.citation: Thromb Res. 2009 Jul;124(3):306-10
references.pmid: 19217651
references.citation: BioDrugs. 1999 Feb;11(2):115-23
references.pmid: 18031120
references.citation: Clin Pharmacol Ther. 1989 Aug;46(2):155-62
references.pmid: 2503283
references.citation: J Clin Invest. 1988 Apr;81(4):1284-91
references.pmid: 2832448
references.citation: N Engl J Med. 1995 Dec 14;333(24):1581-7
references.pmid: 7477192
references.citation: Stroke. 2008 Jan;39(1):87-99
references.pmid: 18032739
references.citation: Thromb Haemost. 1995 Mar;73(3):386-91
references.pmid: 7667820
references.citation: Clin Ther. 1998 Mar-Apr;20(2):307-23
references.pmid: 9589822
references.citation: Stroke. 1985 Nov-Dec;16(6):1022-9
references.pmid: 4089920
references.citation: Magn Reson Med. 2000 Dec;44(6):867-72
references.pmid: 11108623
references.citation: J Thromb Thrombolysis. 2001 May;11(3):223-8
references.pmid: 11577261
references.citation: Acad Radiol. 2005 May;12 Suppl 1:S9-13
references.pmid: 16106538
references.citation: Circulation. 2001 Jul 24;104(4):399-405
references.pmid: 11468200
references.citation: Am J Cardiol. 2006 Dec 18;98(12A):10Q-21Q
references.pmid: 17169625
references.citation: Neurol Res. 2005;27 Suppl 1:S29-35
references.pmid: 16197821
references.citation: Chest. 2004 Sep;126(3 Suppl):549S-575S
references.pmid: 15383484
references.citation: Ultrasound Med Biol. 2008 Nov;34(11):1783-92
references.pmid: 18468773
references.citation: Circulation. 2001 Jul 24;104(4):406-11
references.pmid: 11468201
references.citation: Stroke. 2008 Dec;39(12):3268-76
references.pmid: 18772447
references.citation: Surg Neurol. 2006 Feb;65(2):155-61; discussion 161
references.pmid: 16427412