1 Heparina no fraccionada.Dr Andrés Borda. Hematología Hospital Universitario 12 de Octubre. 2010

2 1916 1918 Jay McLean Acuño el termino heparina- griego “hepar”William Henry Howell L. Emmett Holt McLean J . The thromboplastic action of cephalin . Am J Physiol ; 41 : 1916 William Henry Howell Howell, W.H. & Holt, E. (1918) Two new factors in blood coagulation – heparin and pro-antithrombin. American Journal of Physiology, 47, 328–341. 1918 Annual meeting of the American Physiological Society in 1922 The 12th International Physiological Congress in 1926 Howell’s main interests were the substances controlling blood clotting; he thought there was a balance between a clotting inhibitor (termed antithrombin) and a procoagulant (termed thromboplastin). He believed that the release of cephalin (so called because it was first isolated from canine brain) from platelets and leucocytes neutralised antithrombin, permitting activation of prothrombin by calcium (Howell, 1912) McLean had come up to Baltimore the previous year and was assigned by Howell to examine the chemical purity of cephalin preparations, and to demonstrate that it was cephalin and not a contaminant in the preparation that accounted for the procoagulant activity. After finishing this work early, McLean extracted phosphatides (fat soluble compounds) from canine liver that appeared to demonstrate anticoagulant, properties in vitro and subsequently led to excessive bleeding in experimental animals. McLean then moved to the University of Pennsylvania to research cephalins further under Richard Mills Pearce. In October 1917, he returned to Baltimore but did no further research on the phosphatides he had isolated the previous year. Instead, he continued research on cephalin, feeling that work on a procoagulant rather than an anticoagulant, was better for the ongoing efforts in The Great War. Back in Howell’s laboratories, work on anticoagulants continued. Alongside another medical student L. Emmett Holt Jr, Howell had isolated another fat soluble anticoagulant apparently distinct from that isolated by McLean 2 years previously (Howell & Holt, 1918). The term ‘heparin’ was coined by Howell from the Greek ‘hepar’, or liver, the tissue from which it was first isolated At an annual meeting of the American Physiological Society in 1922, Howell introduced an aqueous extraction protocol for isolating heparin and, at The 12th International Physiological Congress in 1926, he presented refinements to this protocol and identified the watersoluble carbohydrate as glucuronic acid. This he correctly claimed was a compound distinct both to the entity isolated by himself and Holt in 1918 and by McLean in 1916. Heparin Heparin is a highly-sulfated glycosaminoglycan of natural origin. It is also one of the oldest drugs still in widespread use: heparin, along with vitamin K antagonists, have been the main anticoagulant drugs for more than 70 years, as it has been used since the 1930s. Although it was first discovered almost a century ago, many years would have to pass until it could be mass produced and used as an anti-coagulant. The Discovery and development of Heparin Even today, there is still controversy regarding the credit of its discovery: initially attributed to the US physiologist William H. Howell ( ), later authors credited the discovery of heparin to one of his alumnii, Jay McLean ( ), who did research work under the guidance of Howell at the John Hopkins Medical School. In , Jay McLean, then a second-year medicine student, was doing research work under the direction of Howell. McLean isolated a phosphatide (fat soluble compound) from canine liver cells with apparent in vitro anticoagulant properties that caused excess bleeding in experimental animals. However, McLean had to leave college in 1917 because of lack of money. One year later, in 1918, Howell and another of his alumnii, L. Emmett Holt Jr., developed another fat soluble anticoagulant apparently distinct from that isolated by McLean. Howell called it “heparin” (from the greek hepar, liver, after the tissue from which it was first isolated). After further research, they presented at the annual meeting of the American Physiological Society in 1922 an aqueous extraction protocol for isolating the newly discovered entity. In 1926, Howell presented further refinements to that protocol. The final result was a compound different from both the entities isolated by himself and Holt in 1918 and by McLean in 1916. McLean’ initial discovery led some authors (at least until the early 1940s) to state that it was him, and not Howell, who did discover heparin, although indirectly. In fact, McLean himself claimed to have discovered heparin for years, although he waited to do so openly until Howell passed away. Unfortunately, McLean passed away in 1957 while writing his own version of the events (the unpublished paper would be published by Circulation magazine in 1959). Other authors claimed that McLean discovered a phospholipid with anticoagulant activity and not the polysaccharides later isolated by Howell and Emment. However, the latest research (Marcum 1992, 2000) tend to modify that statement, saying that a scientific discovery “is seldom made by an individual in isolation but often occurs in a community of scholars and their intellectual history or traditions”. The conclusion of Marcum and other authors was that, probably, the work of McLean changed the focus of Howell’s research, pointing him to the right direction where to investigate. The compound refined by Howell and his colleagues began to be commercialized in However, clinical tests carried out at the Mayo clinic demonstrated that this preparation caused side effects such as headaches, fever and nausea. Nevertheless, heparin continued to be distributed commercially, although it was a difficult to obtain product that was not highly toxic, and therefore of little medical use. Howell retired in 1931 and did not continued research on heparin. However, in other areas of the globe, there were other scientists working to produce a more refined heparin. In 1928, Canadian physiologist Charles Best ( ; Nobel prize in 1923 for his discovery of insulin along with Frederick Banting) began to show interest in the production of heparin from the Toronto-based Connaught laboratories. By 1933, they had developed a first process to extract heparin from bovine liver. During their research, Best and his colleagues found out that liver, muscle and lung tissues contained the largest quantities of heparin and that the only “tissue” not containing significant quantities of heparin was blood itself. After several years of experiments to use heparin to treat thrombosis in dogs, in 1937 they had developed enough heparin to begin human trials. The development of secure, non-toxic heparin would be carried out in Canada in In April 1937 that newest form of heparin was first injected in a human patient, without secondary effects. Also, in 1929, a Swedish scientist, Dr. Erik Jorpes, visited Best at Canada to observe the production process of insulin; he was also introduced to the heparin research. When he returned to the Karolinska Institut in Stokholm he tried to better purify heparin and thus avoid its side effects. Jorpes published the first conclusions of his research in 1935; by 1936, the Swedish company Vitrium AB was producing parenteral heparin for human use. By 1939, Jay McLean began to have success experimenting with the use of heparin (along with sulfapyridine) in the treatment of endocarditis and gangrene. Also, the same scientific team which developed heparin in Canada noted its potential use in the treatment of embolectomy, splenoctomy, grafts, and pulmonary embolism, since beginning research on heparin. Connaught laboratories continued research on heparin in order to try to develop a protocol for mass-production. However, by the late 1940’s Moloney and Taylor had developed a method to cheaply produce large quantities of purified heparin. In the early 1950s, this discovery led Connaught laboratories to abandon the production of the compound they had pioneered. Since then, heparin has been safely used to prevent blood clotting in surgery patients, as well as to treat dialysis patients. There is only one exception: the heparin adulteration crisis of 2008, which affected thousands of people in eleven countries. The origin of the problem was finally found out to be the raw material processed in China from porcine intestine used in several batches of heparin imported by the US company Scientific Protein Laboratories. The crisis forced the withdrawal of entire batches of heparin distributed by Baxter and other companies. (For additional information on the Chinese heparin crisis, see our wikiheparin). Johns Hopkins Medical School Grasa soluble anticoagulante Acuño el termino heparina- griego “hepar” Protocolo de extracción “ carbohidrato hidrosoluble similar al acido glucoronico”.

3 Heparina hidro soluble producción comercial.Hynson, Westcott, and Dunning. pharmaceutical company in Baltimore Mason, M.C. (1924) A note on the use of heparin in blood transfusion. Journal of Laboratory and Clinical Medicine, 10, 203–206. This water soluble heparin began to be produced commercially by a local pharmaceutical company in Baltimore, Hynson, Westcott, and Dunning, but studies conducted at Mayo Clinic, Minnesota, by Edward Mason demonstrated that this preparation caused side effects including headaches, fevers and nausea (Mason, 1924). Howell was concerned production would cease as its toxic effects might preclude widespread use (Howell & MacDonald, 1930). However, heparin did continue to be available commercially despite these fears, although the pharmaceutical company did not advance its isolation beyond Howell’s original protocol. In 1931, Howell retired from his post at Johns Hopkins and did no further research on heparin 1924 Heparina hidro soluble producción comercial. Efectos adversos (fiebre, nausea y cefalea) No modificación del protocolo de aislamiento. Retiro de Howell (1931)

4 3 paper 1397 Connaught Laboratories, Toronto, 1928-1929 1933Charles Best Charles, A.F. & Scott, D.A. (1933b) Studies on heparin II heparin in various tissues. Journal of Biological Chemistry, 102, 431–435. 1933 Murray, D.W.G., Jaques, L.B., Perrett, T.S. & Best, C.H. (1937) Heparin and the thrombosis of veins following injury. Surgery, 2, 163– 187. 1397 Connaught Laboratories, Toronto, In 1929, Erik Jorpes, a Swedish physiologist visited Best to observe the production of insulin at Toronto. Jorpes was shown around the Connaught Laboratories and introduced to the work on heparin. He subsequently returned to Stockholm and began his own attempt to isolate and characterise the substance. It was not until 1933, four years after Best’s team had begun serious work on the project, that Charles, and his more experienced colleague David Scott, who had served as an assistant director at the Connaught Laboratories, published a series of papers on their work thus far (Charles & Scott, 1933a,b,c). In the first paper (Charles & Scott, 1933a) they outlined a protocol for isolating a crude heparin preparation from bovine liver. To increase the amount of heparin yielded, the tissue had to be autolysed but the smell of the decaying tissue was so bad that the production had to be moved from the laboratories in the city to the local Connaught Farm! Their next paper outlined a survey of extra-hepatic tissues where heparin could be identified, partly because of the high cost of liver (Charles & Scott, 1933b). crystalline form of heparin, there were problems getting consistent results from batch to batch Purificar heparina y reducir o eliminar los efectos adversos. Demostrar la prevención en la formación de trombos. ”Protocolo de aislamiento de hígado-pulmón y musculo” bovino “prevención de formación de trombos en perros”

5 (endocarditis bacteriana)McLean, J., Meyer, B.B.M. & Griffith, J.M. (1941) Heparin in subacute bacterial endocarditis. Reproduction of cases and critical review of the literature. Journal of the American Medical Association, 117, 1870–1875. 1941 Lange, K., Boyd, L.J. & Loewe, L. (1945) The functional pathology of frostbite and the prevention of gangrene in experimental animals and humans. Science, 102, 151–152. McLean, J. & Johnson, A.B. (1946) Gangrene following fracture treated with heparin, papaverine, and intermittent venous occlusion. Surgery, 20, 324–336. McLean, J. & Johnson, A.B. (1946) Gangrene following fracture treated with heparin, papaverine, and intermittent venous occlusion. Surgery, 20, 324–336. 1946 1945 Uso en humanos (endocarditis bacteriana) Manejo de amputación post gangrena. (resultados favorables…) Posible papel en la prevención de la gangrena por congelación.

6 Optimizaron los sistemas de producción y reducción de costos.Drs Peter Moloney and Edith Taylor 1949 early 1950s, Connaught had stopped producing a crucial life-saving product that it had pioneered Exlopración del uso clínico. role.   By 1937 it was clear that Connaught's heparin was a safe, easily available and effective blood anticoagulant.  Best's heparin team had opened the door to such operations as organ transplants and open heart surgery, as well as the artificial kidney that was pioneered by Murray.  Connaught continued to prepare heparin and worked to increase its potency and reduce its price.  By 1949, Drs. Peter Moloney and Edith Taylor were successful and received a patent  for their improved methods of heparin production.  Ironically, this work made heparin more easily produced elsewhere.  Thus, by the early 1950s, Connaught had stopped producing a crucial life-saving product that it had pioneered. Connaught Laboratories' involvement in the Insulin story is well known.  However, Connaught's role in the even more important history of Heparin in the 1930s is much less appreciated.  These dramatic events in medical history share many common elements linked by a strongly cooperative production, research and clinical relationship between Connaught, the University of Toronto's Department of Physiology, and the Toronto General Hospital.  A central figure to both stories was Dr. Charles H. Best ( ).Heparin is a powerful blood anticoagulant that is essential for open heart surgery, organ transplants and for treating dangerous internal blood clots, or thrombosis, which can block blood flow to the lungs with sudden and fatal results.  Heparin was discovered in 1916 at Johns Hopkins University, but it was not practically applied by doctors until the early 1930s when a research team at Connaught, led by Best, developed a method to make available a purified, plentiful and inexpensive supply safe for human use. The Toronto heparin story began in when Best, the new head of the U. of T.'s Physiology Department and an Associate Director of Connaught, decided to break the heparin stalemate and explore its practical value.  At the time only small amounts of heparin, made from dog liver, was available, but it was extremely expensive, toxic and unsafe for humans.  Best thus had two goals: 1) to find a method to produce large amounts of pure heparin; and 2) study the effects of heparin in animals, and then humans, to control thrombosis.  After early work proved encouraging, Best expanded his research team in 1929 to include Drs. Arthur F. Charles ( ), a young organic chemist, and David A. Scott ( ), who was closely involved in insulin production at Connaught.  Soon after Charles and Scott began their work, Dr. Gordon Murray ( ), a prominent surgeon at Toronto General Hospital, joined the team to conduct experimental surgery using heparin. The first task of Charles and Scott was to find a cheaper source of heparin than dog liver.  They turned to beef liver, readily available from local slaughterhouses, and were successful in extracting significant amounts of heparin.  However, a growing pet food industry drove up the price of beef liver, forcing Charles and Scott to try other tissues.  They found that beef lung and intestines were also good sources of heparin; the latter more plentiful and cheap as it was less useful for pet foods.  This work was highly complex, as well as unpleasant since an important part of their method involved letting these tissues "autolyze," or spoil, before the extract could be prepared and purified.  This forced much of the work from the School of Hygiene Building downtown, to the more open environment of Connaught's Dufferin "Farm."  Charles and Scott first reported on this work in the fall of 1933, followed by studies of the still mysterious chemistry of heparin.  Between 1933 and 1936, they succeeded in purifying and then crystallizing heparin into a standardized dry form that could be administered in a salt solution.  Heparin thus became Connaught's second product, after insulin, to be recognized as an international biological standard. Meanwhile, Murray conducted experimental surgery with various animals using Connaught's more potent heparin.  He discovered that heparin definitely cleared up internal blood clots, and also seemed useful for many other dangerous operations where blood coagulated quickly.  The next step was to try heparin on human patients under less predictable conditions.  The first human trials began in May 1935 and soon involved hundreds of complex surgical cases during which Connaught's heparin played an essential and often dramatic life-saving role.   By 1937 it was clear that Connaught's heparin was a safe, easily available and effective blood anticoagulant.  Best's heparin team had opened the door to such operations as organ transplants and open heart surgery, as well as the artificial kidney that was pioneered by Murray.  Connaught continued to prepare heparin and worked to increase its potency and reduce its price.  By 1949, Drs. Peter Moloney and Edith Taylor were successful and received a patent  for their improved methods of heparin production.  Ironically, this work made heparin more easily produced elsewhere.  Thus, by the early 1950s, Connaught had stopped producing a crucial life-saving product that it had pioneered 1950 1950- Optimizaron los sistemas de producción y reducción de costos. Deja de producirlo Otros laboratorios.

7 ? "he encontrado algo opuesto a lo que yo buscaba. Me pareció una sustancia aquí que claramente inhibe la coagulación. ¿No es interesante? Voy a estudiarlo.“ Jay McLean, un joven estudiante de medicina de Boston llegó a John Hopkins Hospital en Baltimore, en el verano de 1915 para hacer la investigación. Se le pidió que tome hígados de perro, molerlas y extraer de ellos una sustancia que promueve la coagulación. Usted recordará que fue cuando la cirugía se fue, la gente sangradas, y los cirujanos querían algo para dar unos toques en para detener el sangrado. Así que Jay McLean comenzó a ir y se extrae todo tipo de cosas fuera de estos hígados Sin embargo, dijo, "he encontrado algo opuesto a lo que yo puse a hacer. Me pareció una sustancia aquí que claramente inhibe la coagulación. ¿No es interesante? Voy a estudiarlo.“ Eso fue lo último que escuchamos de Jay McLean Dos años más tarde, dos profesores de la Universidad Johns Hopkins, Howell y Holt, publican "Dos nuevos factores de coagulación de la sangre: heparina y pro-antitrombina", donde se redescubren la historia de Jay McLean aquí. ¿Qué ha pasado aquí? ¿Quién fue Jay McLean? Una publicación de estudiante sin su profesor. ¿Quiénes fueron los profesores que le robaron su idea? Nunca lo sabremos. Una vez le regalé a un cardiólogo que había sido el editor de la revista muy famosa, Circulation. Él dijo: "Yo sé Jay McLean. Voy a llamarlo. Él sigue siendo un médico en la Florida."

8 (This was as far as Dr. McLean progressed in his history of the discovery of heparin before he developed his fatal illness and died November 14, Ed.) So Jay McLean was asked to write the story of the discovery of heparin. He begins then telling how he was a premedical school student, he needed money, he went to work, and he made this discovery. Then he dropped dead. Boom, like this. He developed a malignant lymphoma and was dead in a couple of weeks. So what happened in the story we will never know. Jaques, L.B. (1978) Addendum: the discovery of heparin. Seminars in Thrombosis and Hemostasis, 4, 350–353 Marcum, J.A. (2000) The origin of the dispute over the discovery of heparin. Journal of the History of Medicine and Allied Sciences, 55, 37–66.

9 In 1963, a plaque was unveiled in Johns Hopkins to commemorate the ‘major contribution [of McLean] to the discovery of heparin in 1916 in collaboration with Professor William Henry Howell’

10

11 Heparina se une a residuos de carga positive en AT.Lento inhibidor sin heparina. Heparina se une a residuos de carga positive en AT. Cambio conformacional en el centro reactivo de la argnina en la AT que convierte la AT de un lento a un rapido inhibidor de proteasas serinas. Polisacarido de alta afinidad. Inh muy rapido. Heparin binds to positively charged residues on AT, producing a conformational change at the AT arginine reactive center that converts AT from a slow to a rapid inhibitor of serine proteases. The arginine reactive center on AT binds covalently to the active center serine of thrombin and other coagulation enzymes, thereby irreversibly inhibiting their procoagulant activity. 5 Heparin then dissociates from AT and is reused Inactivation of clotting enzymes by heparin. Top, ATIII is a slow inhibitor without heparin. Middle, Heparin binds to ATIII through a high-affinity pentasaccharide and induces a conformational change in ATIII, thereby converting ATIII from a slow inhibitor to a very rapid inhibitor. Bottom, ATIII binds covalently to the clotting enzyme, and the heparin dissociates from the complex and can be reused. AT 5 antithrombin. (Reprinted with permission from Hirsh et al. 7 ) El centro reactivo de arginina en AT se une covalente a la serina en el centro activo de la trombina y otras enzimas de la coagulación. (inhibición irreversible de la actividad procoagulante)

12 Tamaño molecular:

13 Interacción y cambio conformacional de heparina y antitrombina.

14 Heparin chains that lack the pentasaccharide sequence have minimal activity when heparin is given in therapeutic concentrations. However, at concentrations higher than those usually administered clinically, heparin chains with or without the pentasaccharide sequence can catalyze thrombin inhibition by heparin cofactor II (HCII), a second plasma cofactor. 12

15 Heparina es un mucopolisacarido altamente sulfatado.Heterogeneo ( tamaño molecular, actividad anticoagulante y farmacocinética). Heparina es un mucopolisacarido altamente sulfatado. 1/3 de las moléculas de heparina posee la secuencia de pentasacaridos . Unidad sacáridos 45 Heparin is a highly sulfated mucopolysaccharide. It is heterogeneous with respect to molecular size, anticoagulant activity, and pharmacokinetic properties ( Table 1 ). Heparin molecules range in molecular weight from 3,000 to 30,000 kDa with a mean of 15,000, which corresponds to approximately 45 saccharide units ( Fig 2 ). 8-10 Only about one-third of the heparin molecules possess the unique pentasaccharide sequence and it is this fraction that is responsible for most of the anticoagulant effect of heparin. 8,11

16

17 Residuo de pentasacaridos.Inactivación de la trombina o atenuación de la generación. La heparina no solo previene la formación de fibrin, pero ademas inhibe la activación inducida por trombina de plaquetas y factores V,VIII y XI.

18

19

20

21

22 The heparin/AT complex inactivates thrombin (factor IIa) and factors Xa, IXa, XIa, and XIIa. 5Heparin catalyzes AT-mediated thrombin inhibition in a nonspecific charge-dependent fashion to form a ternary heparin/AT/thrombin complex. In contrast, to catalyze factor Xa inhibition by AT, heparin needs only to bind to AT. 14 In both cases binding occurs at the unique pentasaccharide sequence found within some heparin molecules. Heparin chains consisting of , 18 saccharide units are too short to bridge AT to thrombin. Consequently, these chains are unable to catalyze thrombin inhibition. However, short heparin chains can catalyze inhibition of factor Xa by AT By inactivating thrombin or attenuating its generation, heparin not only prevents fibrin formation but also inhibits thrombin-induced activation of platelets and factors V, VIII, and XI In vitro, heparin binds to platelets and, depending on the experimental conditions, can either induce or inhibit platelet aggregation. 22,23 High-molecular weight heparin fractions with low affinity for AT have a greater effect on platelet function than low molecular- weight fractions with high AT affinity. 24 Heparin can prolong the bleeding time in humans, 25 and it enhances blood loss from the microvasculature in rabbits. 20,26,27 The interaction of heparin with platelets 26 and endothelial cells 20 may contribute to heparin-induced bleeding by mechanisms independent of its anticoagulant effect. 2 In addition to its anticoagulant effects, heparin attenuates the proliferation of vascular smooth muscle cells, 28,29 inhibits osteoblast formation, and activates osteoclasts; these last two effects promote bone loss. 30,31 Heparin-induced thrombocytopenia (HIT) is the most important nonhemorrhagic side effect of . This is discussed by Linkins et al 32 in this supplement.

23 Otros efectos no anticoagulantes de la heparinaAtenúa a proliferación de las células del musculo liso vascular. Promueve la perdida ósea. Inhibe la formación del osteoblastos. Activa osteoclastos. Bhandari Met al. . Thromb Haemost ; 80 ( 3 ): Shaughnessy SG et al . Blood ; 86( 4):

24 Farmacocinetica. No biodisponibilidad oral.La biodisponibilidad subcutánea es reducida. ( requiere dosis más altas). Pini M , Pattachini C , Quintavalla R , et al . Subcutaneous vs intravenous heparin in the treatment of deep venous thrombosis—a randomized clinical trial . Thromb Haemost ; 64 ( 2 ): If an immediate anticoagulant effect is required, a higher initial subcutaneous dose of heparin can be administered. 35 Alternatively, an IV bolus of heparin can be given in conjunction with the first subcutaneous dose. Administration by subcutaneous injection in low doses 36 (eg, 5,000 units q12h ), moderate doses of 12,500 units q12h, 37 or 15,000 units q12h reduces the plasma recovery of heparin. 33 However, at high therapeutic doses ( . 35,000 units q24h) plasma recovery is almost complete. 34

25 Unión a células endoteliales, macrófagos y unión al FVW.Unión a proteinas plasmáticas diferentes a AT. (variabilidad de la respuesta a heparina). Mecanismos de eliminación. Rápido y saturable. Lento no saturable de primer orden. Respuesta no lineal a dosis en ascenso . t1/ min : 25 u/kg t1/ min : 100 u/kg t1/ min: 400u /kg Unión a células endoteliales, macrófagos y unión al FVW. heparin binds to a number of plasma proteins other than AT, reducing its anticoagulant activity. This phenomenon contributes to the variability of the anticoagulant response to heparin among patients with thromboembolic disorders 38 and to the laboratory phenomenon of heparin resistance. Heparin also binds to endothelial cells 40 and macrophages, a property that further complicates its pharmacokinetics. Binding of heparin to von Willebrand factor also inhibits von Willebrand factor dependent platelet function. 41 Unión a celulas endoteliales, macrófagos y unión al FVW. Heparin is cleared through a combination of a rapid saturable and a much slower first-order mechanism ( Fig 3 ) The saturable phase of heparin clearance is believed to be due to binding to endothelial cell receptors 45 and macrophages. 46 Bound heparin is internalized and depolymerized ( Fig 4 ). 47,48 The slower nonsaturable mechanism of clearance is largely renal. At therapeutic doses, a large proportion of heparin is cleared through the rapid saturable, dose-dependent mechanism. The complex kinetics of clearance render the anticoagulant response to heparin nonlinear at therapeutic doses, with both the intensity and duration of effect rising disproportionately with increasing dose. Thus, the apparent biologic half-life of heparin increases from approximately 30 min after an IV bolus of 25 units/kg, to 60 min with an IV bolus of 100 units/kg, to 150 min with a bolus of 400 units/kg t1/ min : 25 u/kg t1/ min : 100 u/kg t1/ min: 400u /kg El mecanismo lento no saturable de clearance es renal. A dosis terapeutica, una gran proporción de heparina es eliminada por mecanismo rapidamente saturable, mecanismo dosis dependiente. La cinetica compelja de la heparina , hace que la respuesta anticoagulante de la heparina a dosis terapeutica no sea lineal. Haceindo que la intensidad y duración del efecto aumente desproporcionadamente con el increment de la dosis.

26 Sitios de unión de la heparina.Cuando la heparina entra en circulación, la heparina se une a proteínas ( otras rpoetinas plasmáticas), celulas endoteliales, macrófagos y ATIII. Solo la heparina con el pentasacarido de alta afinidad se une a la ATIII, per la unión a otras proteínas y celulas no es especifico y ocurre independiente del sitio de unión ATIII.

27 Dosis. (TEV) Intravenosa. Subcutanea.Dosis inicial IV (80 U/kg bolo y 18 U/kg/h ) Bolo de 5,000 U seguido de U/dia. Bolo inicial IV 5000 U seguido por 250 U/kg/12h SC 333 U/kg SC seguido de 250 U/kg/12h SC Kearon C , Ginsberg JS , Julian JA , et al ; Fixed-Dose Heparin (FIDO) Investigators . Comparison of fi xed-dose weightadjusted unfractionated heparin and low-molecular-weight heparin for acute treatment of venous thromboembolism . JAMA ; 296 ( 8 ): Prandoni P , Carnovali M , Marchiori A ; Galilei Investigators . Subcutaneous adjusted-dose unfractionated heparin vs fi xeddose low-molecular-weight heparin in the initial treatment of venous thromboembolism . Arch Intern Med ; 164 ( 10 ): Raschke. Ann Intern Med ; 119 ( 9 ): Cruickshanket al.. Arch Intern Med ; 151 ( 2 ):

28 Control de anticoagulación.ACT (tiempo coagulación activado) es usado para monitorizar el control de la heparina en PCI y Bypass coronario. aPTT. increased by recent surgery, trauma, invasive procedures, or concomitant hemostatic defects. 63 In hospitalized patients, increasing number of comorbidities, age . 60 y, supratherapeutic clotting times, and worsening hepatic dysfunction increase the risk of anticoagulant-associated bleeding In the study that established a therapeutic range for the aPTT, 66 an aPTT ratio of 1.5 to 2.5 corresponded to a heparin level of 0.2 to 0.4 units by protamine titration and a heparin level of 0.3 to 0.7 units measured by an anti-Xa assay Con niveles de 0.3 to 0.7 anti-Xa units/mL Tiene un ratio de to veces el control

29 The results of a randomized trial in patients with VTE that showed that unmonitored weight-adjusted subcutaneous heparin given twice daily in high doses was as safe and effective as unmonitored, weight-adjusted LMWH challenge the requirement for aPTT monitoring of heparin administered subcutaneously

30 Pharmacotherapy 2004;24(8 Pt 2):142S–145S)

31 Pharmacotherapy 2004;24(8 Pt 2):142S–145S)

32 Dosis. (Sindrome coronario agudo)ACA ( SCA sin elevación del ST) Bolo 60 a 70 U/kg (max 5000 U), seguido por infusión de 12 a 15 U/kg/h (máximo 1000 U/h) . 53 SCA con elevación ST Bolo 60 U/kg ( maximo 4000 U) y seguido de 12 U/kg/h (maximo 1000 U/h) sumado a agente fibrinolitico. 54 Ryan T , Antman E , Brooks N , et al update: ACC/ AHA guidelines for the management of patients with acute myocardial infarction. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines . J Am Coll Cardiol ; 34 (3): Braunwald E, Antman E , Beasley J , et al . ACC/AHA Guidelines for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction . A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. J Am Coll Cardiol ; 36 (3):

33 Resistencia a la heparina.Causas. Deficiencia de Antitrombina. Incremento del clerance de heparina. Elevación de la proteínas de unión a la heparina. Altos niveles del factor VIII. Aumento de fibrinógeno. Aprotinina. Nitroglicerina*** Situación en la cual los pacientes requieren dosis inusualmente altas de heparina para alcanzar el aPTT terapéutico.

34 Resistencia a la heparina.Es razonable ajustar la dosis de heparina a niveles de anti-Xa, en pacientes que requieren altas dosis de heparina para alcanzar un nivel aPTT terapéutico.

35 Limitaciones de la heparina.Activación plaquetaria mediada inmune. Trombopenia inducida de la heparina. Efecto en el metabolismo óseo. Osteoporosis. Although hypersensitivity reactions to heparin are uncommon, an unusually high number of adverse events with heparin were reported in North America in Typically, these events consisted of hypotension, nausea, and shortness of breath within 30 min of heparin administration. An investigation into this problem conducted by the US Centers for Disease Control identifi ed the cause of these reactions to be a contaminant in heparin manufactured in China. The contaminant was an oversulfated chondroitin sulfate oversulfated chondroitin sulfate induces hypotension by promoting the activation of factor XII and the subsequent generation of bradykinin. 95 Heparin therapy can also cause elevations of serum transaminases. The increase in transaminases is usually transient and is not associated with an increase in bilirubin; it is presumed to have no clinical consequences. 96 Necrosis, alopecia y reacciones de hipersensibilidad.*** (2007) Manifestaciones cutáneas. Elevación de transaminasas transitoria.

36 Revertir el efecto anticoagulante de la heparina.Sulfato de protamina es una proteína básica derivada de esperma de pescado, se une a la heparina en forma de sal estable. 1 mg de sulfato de protamina neutraliza aproximadamente 100 Unidades de heparina. Para evitar reacciones adversas a la protamina, administrar lentamente. Therefore, a patient who bleeds immediately after receiving an IV bolus of 5,000 units of heparin should receive about 50 mg of protamine sulfate.

37 Revertir el efecto anticoagulante de la heparina.Solo la heparina administrada en las horas previas (2 h), son consideradas para calcular la dosis de protamina necesaria. Protamina : Vida media 7 min. Heparina: vida media 60 a 90 min. La aPTT puede ser usado para valorar la efectividad de la neutralización del efecto anticoagulante. Therefore, a patient receiving a continuous IV infusion of heparin at 1,250 units/h requires approximately 30 mg of protamine sulfate to neutralize the heparin that was given in the past 2 to 2.5 h. A number of other substances or devices have been shown to neutralize the anticoagulant effects of UFH. These include hexadimethrine (Polybrene), 102,103 heparinase (Neutralase), 104 PF4, 105,106 extracorporeal heparin removal devices, 107 and synthetic protamine variants. 108 None of these is approved for clinical use. La neutralización de heparina subcutánea puede requerir infusión prolongadas de sulfato de protamina

38 Valoración del riesgo de reacción a protaminaUso previo de insulina que contenía sulfato de protamina. Vasectomia. Historia de sensibilidad a pescado Premedicar con corticosteroides y antihistamínicos. Patients who have previously received protamine sulfate-containing insulin, have undergone vasectomy, or have known sensitivity to fi sh are at increased risk to have preformed antibodies against protamine sulfate and to suffer from allergic reactions, including anaphylaxis. 100,101 Such reactions are uncommon, but if there is concern about a potential protamine sulfate allergy, patients can be pretreated with corticosteroids and antihistamines.