Heparin

INDICATIONS AND USAGE Heparin Sodium Injection is indicated for: • Prophylaxis and treatment of venous thrombosis and pulmonary embolism; • Prevention of postoperative deep venous thrombosis and pulmonary embolism in patients undergoing major abdominothoracic surgery or who, for other reasons, are at risk of developing thromboembolic disease; • Atrial fibrillation with embolization; • Treatment of acute and chronic consumptive coagulopathies (disseminated intravascular coagulation); • Prevention of clotting in arterial and cardiac surgery; • Prophylaxis and treatment of peripheral arterial embolism. • Anticoagulant use in blood transfusions, extracorporeal circulation, and dialysis procedures. HEPARIN SODIUM INJECTION is an anticoagulant indicated for ( 1 ) • Prophylaxis and treatment of venous thrombosis and pulmonary embolism • Prevention of postoperative deep venous thrombosis and pulmonary embolism in patients undergoing major abdominothoracic surgery or who, for other reasons, are at risk of developing thromboembolic disease • Atrial fibrillation with embolization • Treatment of acute and chronic consumptive coagulopathies (disseminated intravascular coagulation) • Prevention of clotting in arterial and cardiac surgery • Prophylaxis and treatment of peripheral arterial embolism • Use as an anticoagulant in blood transfusions, extracorporeal circulation, and dialysis procedures

DOSAGE AND ADMINISTRATION Recommended Adult Dosages: Therapeutic Anticoagulant Effect with Full-Dose Heparin † ( 2.4 ) Deep Subcutaneous (Intrafat) Injection Use a different site for each injection Initial Dose 5,000 units by intravenous injection, followed by 10,000 to 20,000 units of a concentrated solution, subcutaneously Every 8 hours or Every 12 hours 8,000 to 10,000 units of a concentrated solution 15,000 to 20,000 units of a concentrated solution Intermittent Intravenous Injection Initial dose 10,000 units, either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP Every 4 to 6 hours 5,000 to 10,000 units, either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP Intravenous Infusion Initial dose 5,000 units by intravenous injection Continuous 20,000 to 40,000 units/24 hours in 1000 mL of 0.9% Sodium Chloride Injection, USP (or in any compatible solution) for infusion † Based on 150 lb (68 kg) patient. Adjust dose based on laboratory monitoring. 2.1 Preparation for Administration Confirm the choice of the correct Heparin Sodium Injection vial to ensure that the 1 mL vial is not confused with a “catheter lock flush” vial or other 1 mL vial of incorrect strength [s ee Warnings and Precautions (5.1) ] . Confirm the selection of the correct formulation and strength prior to administration of the drug. To lessen this risk, the 1 mL vial includes a red cautionary label that extends above the main label. Read the cautionary statement and confirm that you have selected the correct medication and strength. Then locate the “Tear Here” point on the label, and remove this red cautionary label prior to removing the flip-off cap. When heparin is added to an infusion solution for continuous intravenous administration, invert the container repeatedly to ensure adequate mixing and prevent pooling of the heparin in the solution. Inspect parenteral drug products visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Use only if solution is clear and the seal is intact. Do not use if solution is discolored or contains a precipitate. Administer Heparin Sodium Injection by intermittent intravenous injection, intravenous infusion, or deep subcutaneous (intrafat, i.e., above the iliac crest or abdominal fat layer) injection. Do not administer Heparin Sodium Injection by intramuscular injection because of the risk of hematoma at the injection site [ see Adverse Reactions (6) ]. 2.3 Laboratory Monitoring for Efficacy and Safety Adjust the dosage of Heparin Sodium Injection according to the patient’s coagulation test results. Dosage is considered adequate when the activated partial thromboplastin time (aPTT) is 1.5 to 2 times normal or when the whole blood clotting time is elevated approximately 2.5 to 3 times the control value. When initiating treatment with Heparin Sodium Injection by continuous intravenous infusion, determine the coagulation status (aPTT, INR, platelet count) at baseline and continue to follow aPTT approximately every 4 hours and then at appropriate intervals thereafter. When the drug is administered intermittently by intravenous injection, perform coagulation tests before each injection during the initiation of treatment and at appropriate intervals thereafter. After deep subcutaneous (intrafat) injections, tests for adequacy of dosage are best performed on samples drawn 4 to 6 hours after the injection. Periodic platelet counts and hematocrits are recommended during the entire course of heparin therapy, regardless of the route of administration. 2.4 Therapeutic Anticoagulant Effect with Full-Dose Heparin The dosing recommendations in Table 1 are based on clinical experience. Although dosages must be adjusted for the individual patient according to the results of suitable laboratory tests, the following dosage schedules may be used as guidelines: Table 1: Recommended Adult Full-Dose Heparin Regimens for Therapeutic Anticoagulant Effect METHOD OF ADMINISTRATION FREQUENCY RECOMMENDED DOSE [based on 150 lb (68 kg) patient] Deep Subcutaneous (Intrafat) Injection Initial dose 5,000 units by intravenous injection, followed by 10,000 to 20,000 units of a concentrated solution, subcutaneously A different site should be used for each injection to prevent the development of massive hematoma Every 8 hours or 8,000 to 10,000 units of a concentrated solution Every 12 hours 15,000 to 20,000 units of a concentrated solution Intermittent Intravenous Injection Initial dose 10,000 units, either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP Every 4 to 6 hours 5,000 to 10,000 units, either undiluted or in 50 to 100 mL of 0.9% Sodium Chloride Injection, USP Intravenous Infusion Initial dose 5,000 units by intravenous injection Continuous 20,000 to 40,000 units/24 hours in 1000 mL of 0.9% Sodium Chloride Injection, USP (or in any compatible solution) for infusion 2.5 Pediatric Use Do not use benzyl alcohol-preserved drugs in neonates and infants. Use preservative-free Heparin Sodium Injection in neonates and infants [ see Warnings and Precautions (5.4) ]. There are no adequate and well controlled studies on heparin use in pediatric patients. Pediatric dosing recommendations are based on clinical experience. In general, the following dosage schedule may be used as a guideline in pediatric patients: Initial Dose 75 to 100 units/kg (Intravenous bolus over 10 minutes) Maintenance Dose Infants: 25 to 30 units/kg/hour; Infants < 2 months have the highest requirements (average 28 units/kg/hour) Children > 1 year of age: 18 to 20 units/kg/hour; Older children may require less heparin, similar to weight-adjusted adult dosage Monitoring Adjust heparin to maintain APTT of 60 to 85 seconds, assuming this reflects an anti-Factor Xa level of 0.35 to 0.70 2.6 Cardiovascular Surgery Patients undergoing total body perfusion for open-heart surgery should receive an initial dose of not less than 150 units of heparin sodium per kilogram of body weight. Frequently, a dose of 300 units per kilogram is used for procedures estimated to last less than 60 minutes, or 400 units per kilogram for those estimated to last longer than 60 minutes. 2.7 Low-Dose Prophylaxis of Postoperative Thromboembolism The most widely used dosage has been 5,000 units 2 hours before surgery and 5,000 units every 8 to 12 hours thereafter for 7 days or until the patient is fully ambulatory, whichever is longer. Administer the heparin by deep subcutaneous (intrafat, i.e., above the iliac crest or abdominal fat layer, arm, or thigh) injection with a fine (25 to 26-gauge) needle to minimize tissue trauma. 2.8 Blood Transfusion Add 450 USP units to 600 USP units of heparin sodium per 100 mL of whole blood to prevent coagulation. Usually, 7,500 USP units of heparin sodium are added to 100 mL of 0.9% Sodium Chloride Injection, USP (or 75,000 USP units per 1000 mL of 0.9% Sodium Chloride Injection, USP) and mixed; from this sterile solution, 6 mL to 8 mL are added per 100 mL of whole blood. 2.9 Converting to Warfarin To ensure continuous anticoagulation when converting from Heparin Sodium Injection to warfarin, continue full heparin therapy for several days until the INR (prothrombin time) has reached a stable therapeutic range. Heparin therapy may then be discontinued without tapering [see Drug Interactions (7.1) ] . 2.10 Converting to Oral Anticoagulants other than Warfarin For patients currently receiving intravenous heparin, stop intravenous infusion of heparin sodium immediately after administering the first dose of oral anticoagulant; or for intermittent intravenous administration of heparin sodium, start oral anticoagulant 0 to 2 hours before the time that the next dose of heparin was to have been administered. 2.11 Extracorporeal Dialysis Follow equipment manufacturer's operating directions carefully. A dose of 25 units/kg to 30 units/kg followed by an infusion rate of 1,500 units/hour to 2,000 units/hour

WARNINGS AND PRECAUTIONS • Hemorrhage: Fatal hemorrhages have occurred. Monitor for signs of bleeding and manage promptly. ( 5.1 ) • HIT and HITT: Monitor for signs and symptoms and discontinue if indicative of HIT or HITT. ( 5.2 ) • Thrombocytopenia: Monitor platelet count during therapy; discontinue heparin if HIT or HITT is suspected. ( 5.4 ) • Heparin Resistance: Increased resistance to heparin is frequently encountered in fever, thrombosis, thrombophlebitis, infections with thrombosing tendencies, myocardial infarction, cancer and in postsurgical patients. ( 5.5 ) • Hypersensitivity Reactions: Use in patients with prior reactions only in life-threatening situations. ( 5.6 ) • Increased Risk of Bleeding in Older Patients, Especially Women: A higher incidence of bleeding has been reported in patients, particularly women, over 60 years of age. ( 5.7 ) • Hyperkalemia: Measure blood potassium in patients at risk of hyperkalemia before starting heparin therapy and periodically in all patients. ( 5.8 ) • Elevations of Serum Aminotransferases: Interpret elevation of these enzymes with caution. ( 5.9 ) • Laboratory Tests: Periodic platelet counts, hematocrits, and tests for occult blood in stool are recommended during the entire course of heparin therapy, regardless of the route of administration. ( 5.10 ) 5.1 Hemorrhage Avoid using heparin in the presence of major bleeding, except when the benefits of heparin therapy outweigh the potential risks. Hemorrhage can occur at virtually any site in patients receiving heparin. Fatal hemorrhages have occurred. An unexplained fall in hematocrit or fall in blood pressure, or any other unexplained symptom should lead to serious consideration of a hemorrhagic event. Use heparin sodium with caution in disease states in which there is increased risk of hemorrhage, including: • Cardiovascular — Subacute bacterial endocarditis. Severe hypertension. • Surgical — During and immediately following (a) spinal tap or spinal anesthesia or (b) major surgery, especially involving the brain, spinal cord or eye. • Hematologic — Conditions associated with increased bleeding tendencies, such as hemophilia, thrombocytopenia and some vascular purpuras. • Gastrointestinal — Ulcerative lesions and continuous tube drainage of the stomach or small intestine. • Patients with hereditary antithrombin III deficiency receiving concurrent antithrombin III therapy – The anticoagulant effect of heparin is enhanced by concurrent treatment with antithrombin III (human) in patients with hereditary antithrombin III deficiency. To reduce the risk of bleeding, reduce the heparin dose during concomitant treatment with antithrombin III (human). • Other — Menstruation, liver disease with impaired hemostasis. 5.2 Heparin-Induced Thrombocytopenia and Heparin-Induced Thrombocytopenia With Thrombosis Heparin-induced thrombocytopenia (HIT) is a serious immune-mediated reaction. HIT occurs in patients treated with heparin and is due to the development of antibodies to a platelet Factor-4-heparin complex that induce in vivo platelet aggregation. HIT may progress to the development of venous and arterial thromboses, a condition referred to as heparin-induced thrombocytopenia with thrombosis (HITT). Thrombotic events may also be the initial presentation for HITT. These serious thromboembolic events include deep vein thrombosis, pulmonary embolism, cerebral vein thrombosis, limb ischemia, stroke, myocardial infarction, mesenteric thrombosis, thrombus formation on a prosthetic cardiac valve, renal arterial thrombosis, skin necrosis, gangrene of the extremities that may lead to amputation, and possibly death. Once HIT or HITT is diagnosed or strongly suspected, discontinue all heparin sources (including heparin flushes) and use an alternative anticoagulant. Immune-mediated HIT is diagnosed based on clinical findings supplemented by laboratory tests confirming the presence of antibodies to heparin, or platelet activation induced by heparin. Obtain platelet counts at baseline and periodically during heparin administration. A drop in platelet count greater than 50% from baseline is considered indicative of HIT. Platelet counts begin to fall 5 to 10 days after exposure to heparin in heparin–naive individuals and reach a threshold by days 7 to 14. In contrast, “rapid onset” HIT can occur very quickly (within 24 hours following heparin initiation), especially in patients with a recent exposure to heparin (i.e., previous 3 months). Thrombosis development shortly after documenting thrombocytopenia is a characteristic finding in almost half of all patients with HIT. If the platelet count falls below 100,000/mm 3 or if recurrent thrombosis develops, promptly discontinue heparin, evaluate for HIT and HITT, and, if necessary, administer an alternative anticoagulant. HIT or HITT can occur up to several weeks after the discontinuation of heparin therapy. Patients presenting with thrombocytopenia or thrombosis after discontinuation of heparin sodium should be evaluated for HIT or HITT. 5.3 Unresponsiveness to Heparin with Concomitant Use With Andexanet Alfa Unresponsiveness to unfractionated heparin leading to non-prolongation of activated clotting times and serious thrombotic events has occurred when unfractionated heparin was administered after use of andexanet alfa for the reversal of direct Factor Xa inhibitors (apixaban and rivaroxaban). Avoid use of heparin after use of andexanet alfa. Use an alternative anticoagulant to heparin [see Drug Interactions (7.3) ] . 5.4 Thrombocytopenia Thrombocytopenia in patients receiving heparin has been reported at frequencies up to 30%. It can occur 2 to 20 days (average 5 to 9) following the onset of heparin therapy. Obtain platelet counts before and periodically during heparin therapy. If the count falls below 100,000/mm 3 or if recurrent thrombosis develops, promptly discontinue heparin, evaluate for HIT and HITT, and, if necessary, administer an alternative anticoagulant [see Warnings and Precautions (5.2) ]. 5.5 Heparin Resistance Increased resistance to heparin is frequently encountered in fever, thrombosis, thrombophlebitis, infections with thrombosing tendencies, myocardial infarction, cancer, in postsurgical patients , and patients with antithrombin deficiency . Consider measurement of antithrombin levels if heparin resistance is suspected. Monitor coagulation tests frequently in such patients. It may be necessary to adjust the dose of heparin based on coagulation test monitoring, such as anti-Factor Xa levels and/or partial thromboplastin time. 5.6 Hypersensitivity Reactions Hypersensitivity reactions with chills, fever, and urticaria as the most usual manifestations and also asthma, rhinitis, lacrimation, and anaphylactoid reactions have been reported. Patients with documented hypersensitivity to heparin should be given the drug only in clearly life-threatening situations. Because Heparin Sodium in Sodium Chloride Injection is derived from animal tissue, it should be used with caution in patients with a history of allergy to pork products. 5.7 Increased Risk of Bleeding in Older Patients, Especially Women A higher incidence of bleeding has been reported in patients, particularly women, over 60 years of age [see Use in Specific Populations (8.5) ] . 5.8 Hyperkalemia Heparin can suppress adrenal secretion of aldosterone leading to hyperkalemia, particularly in patients with diabetes mellitus, chronic renal failure, pre-existing metabolic acidosis, a raised plasma potassium, or taking potassium sparing drugs. The risk of hyperkalemia appears to increase with duration of therapy but is usually reversible upon discontinuation of heparin. Measure blood potassium in patients at risk of hyperkalemia before starting heparin therapy and periodically in all patients treated for more than 5 days or earlier as deemed fit by the clinician. 5.9 Elevations of Serum Aminotransferases Significant elevations of aspartate aminotransferase (AST) and

CONTRAINDICATIONS The use of HEPARIN SODIUM INJECTION is contraindicated in patients: • History of heparin-induced thrombocytopenia and heparin-induced thrombocytopenia and thrombosis • History of thrombocytopenia with pentosan polysulfate • Known hypersensitivity to heparin or pork products (e.g., anaphylactoid reactions) [see Adverse Reactions (6.1) ] • In whom suitable blood coagulation tests (e.g., whole-blood clotting time, partial thromboplastin time) cannot be performed at appropriate intervals. This contraindication refers to full-dose heparin regimens only; there is usually no need to monitor coagulation parameters in patients receiving low-dose heparin • An uncontrollable bleeding state [see Warnings and Precautions (5.2) ] , except when this is due to disseminated intravascular coagulation • History of heparin-induced thrombocytopenia (HIT) or heparin-induced thrombocytopenia and thrombosis (HITTS) ( 4 ) • History of thrombocytopenia with pentosan polysulfate ( 4 ) • Known hypersensitivity to heparin or pork products ( 4 ) • In whom suitable blood coagulation tests cannot be performed at appropriate intervals ( 4 ) • An uncontrollable bleeding state, except when this is due to disseminated intravascular coagulation ( 4 )

DRUG INTERACTIONS • Drugs that interfere with coagulation, platelet aggregation or drugs that counteract coagulation may induce bleeding ( 7 ) • Andexanet alfa may reduce the efficacy of heparin when used concomitantly ( 7.3 ) 7.1 Oral Anticoagulants Heparin sodium may prolong the one-stage prothrombin time. Therefore, when heparin sodium is given with dicumarol or warfarin sodium, a period of at least 5 hours after the last intravenous dose or 24 hours after the last subcutaneous dose should elapse before blood is drawn if a valid prothrombin time is to be obtained. 7.2 Platelet Inhibitors Drugs such as acetylsalicylic acid, dextran, phenylbutazone, ibuprofen, indomethacin, dipyridamole, hydroxychloroquine and others that interfere with platelet-aggregation reactions (the main hemostatic defense of heparinized patients) may induce bleeding and should be used with caution in patients receiving heparin sodium. 7.3 Unresponsiveness to Heparin With Concomitant Use With Andexanet Alfa Andexanet binds to heparin-bound antithrombin III (ATIII) and may reduce the anticoagulant effect of heparin. Unresponsiveness to unfractionated heparin may lead to serious and life-threatening thrombotic events. Use of andexanet alfa as an antidote for heparin has not been established. Avoid use of heparin after use of andexanet alfa for the reversal of direct Factor Xa inhibitors (apixaban and rivaroxaban). If anticoagulation is needed, use an alternative anticoagulant to heparin [see Warnings and Precautions (5.4) ] . 7.4 Other Interactions Digitalis, tetracyclines, nicotine, or antihistamines, or intravenous nitroglycerin may partially counteract the anticoagulant action of heparin sodium. Intravenous nitroglycerin administered to heparinized patients may result in a decrease of the partial thromboplastin time with subsequent rebound effect upon discontinuation of nitroglycerin. Careful monitoring of partial thromboplastin time and adjustment of heparin dosage are recommended during coadministration of heparin and intravenous nitroglycerin. 7.5 Drug/Laboratory Tests Interactions Prothrombin time – Heparin sodium may prolong the one-stage prothrombin time. Therefore, when heparin sodium is given with warfarin, allow a period of at least 5 hours after the last intravenous dose or 24 hours after the last subcutaneous dose of heparin to elapse before blood is drawn to obtain a valid prothrombin time. Hyperaminotransferasemia Significant elevations of aminotransferase AST (SGOT) and ALT (SGPT) levels have occurred in a high percentage of patients (and healthy subjects) who have received heparin. Since aminotransferase determinations are important in the differential diagnosis of myocardial infarction, liver disease and pulmonary emboli, rises that might be caused by drugs (like heparin) should be interpreted with caution.

ADVERSE REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: • Fatal Medication Errors [see Warnings and Precautions (5.1) ] • Hemorrhage [see Warnings and Precautions (5.2) ] • Heparin-induced Thrombocytopenia (HIT) (With or Without Thrombosis) [see Warnings and Precautions (5.3) ] • Thrombocytopenia [see Warnings and Precautions (5.5) ] • Heparin Resistance [see Warnings and Precautions (5.7) ] • Hypersensitivity Reactions [see Warnings and Precautions (5.8) ] • Hyperkalemia [see Warnings and Precautions (5.9) ] Most common adverse reactions are hemorrhage, thrombocytopenia, HIT (With or Without Thrombosis), local irritation, hypersensitivity reactions, and elevations of aminotransferase levels. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer Inc. at 1-800-438-1985 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Postmarketing Experience The following adverse reactions have been identified during post-approval use of heparin sodium. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Hemorrhage Hemorrhage is the chief complication that may result from heparin therapy [see Warnings and Precautions (5.2) ]. An overly prolonged clotting time or minor bleeding during therapy can usually be controlled by withdrawing the drug [see Overdosage (10) ] . Gastrointestinal or urinary tract bleeding during anticoagulant therapy may indicate the presence of an underlying occult lesion. Bleeding can occur at any site but certain specific hemorrhagic complications may be difficult to detect: a. Adrenal hemorrhage, with resultant acute adrenal insufficiency, has occurred during anticoagulant therapy. Therefore, such treatment should be discontinued in patients who develop signs and symptoms of acute adrenal hemorrhage and insufficiency. Initiation of corrective therapy should not depend on laboratory confirmation of the diagnosis, since any delay in an acute situation may result in the patient's death. b. Ovarian (corpus luteum) hemorrhage developed in a number of women of reproductive age receiving short- or long-term anticoagulant therapy. This complication if unrecognized may be fatal. c. Retroperitoneal hemorrhage. Thrombocytopenia, Heparin-induced Thrombocytopenia (HIT) (With or Without Thrombosis) and Delayed Onset of HIT (With or Without Thrombosis): [see Warnings and Precautions (5.3 , 5.5 )] Local Irritation Local irritation, erythema, mild pain, hematoma or ulceration may follow deep subcutaneous (intrafat) injection of heparin sodium. These complications are much more common after intramuscular use, and such use is not recommended. Hypersensitivity Generalized hypersensitivity reactions have been reported with chills, fever, and urticaria as the most usual manifestations, and asthma, rhinitis, lacrimation, headache, nausea and vomiting, and anaphylactoid reactions, including shock, occurring more rarely. Itching and burning, especially on the plantar site of the feet, may occur [see Warnings and Precautions (5.8) ] . Episodes of painful, ischemic, and cyanosed limbs have been reported with heparin use. Metabolism and Nutrition Disorders – Hyperkalemia. Elevations of Serum Aminotransferases Significant elevations of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels have occurred in a high percentage of patients (and healthy subjects) who have received heparin. Others Osteoporosis following long-term administration of high doses of heparin, cutaneous necrosis after systemic administration, suppression of aldosterone synthesis, delayed transient alopecia, priapism, and rebound hyperlipemia on discontinuation of heparin sodium have also been reported. Reactions which may occur because of the solution or the technique of administration include febrile response, infection at the site of injection, venous thrombosis or phlebitis extending from the site of injection, extravasation, and hypervolemia.

Mechanism of Action Heparin inhibits reactions that lead to the clotting of blood and the formation of fibrin clots both in vitro and in vivo. Heparin acts at multiple sites in the normal coagulation system. Small amounts of heparin in combination with antithrombin III (heparin cofactor) can inhibit thrombosis by inactivating activated Factor X and inhibiting the conversion of prothrombin to thrombin. Once active thrombosis has developed, larger amounts of heparin can inhibit further coagulation by inactivating thrombin and preventing the conversion of fibrinogen to fibrin. Heparin also prevents the formation of a stable fibrin clot by inhibiting the activation of the fibrin stabilizing factor. Heparin does not have fibrinolytic activity; therefore, it will not lyse existing clots. 12.2 Pharmacodynamics Bleeding time is usually unaffected by heparin. Clotting time is prolonged by full therapeutic doses of heparin; in most cases it is not measurably affected by low doses of heparin. 12.3 Pharmacokinetics Absorption Heparin is not absorbed through gastrointestinal tract and therefore administered via parenteral route. Peak plasma concentration and the onset of action are achieved immediately after intravenous administration. Distribution Heparin is highly bound to antithrombin, fibrinogens, globulins, serum proteases and lipoproteins. The volume of distribution is 0.07 L/kg. Elimination Metabolism Heparin does not undergo enzymatic degradation. Excretion Heparin is mainly cleared from the circulation by liver and reticuloendothelial cells mediated uptake into extravascular space. Heparin undergoes biphasic clearance, a) rapid saturable clearance (zero order process due to binding to proteins, endothelial cells and macrophage) and b) slower first order elimination. The plasma half-life is dose-dependent, and it ranges from 0.5 to 2 h. Specific Populations Geriatric patients Patients over 60 years of age, following similar doses of heparin, may have higher plasma levels of heparin and longer activated partial thromboplastin times (APTTs) compared with patients under 60 years of age [see Use in Specific Populations (8.5)].