Heparin

Uses

Heparin sodium is used for:

Atrial fibrillation with embolization:

• Treatment of acute and chronic consumption coagulopathies (disseminated intravascular coagulation);
• Prevention of clotting in arterial and heart surgery;
• Anticoagulant therapy in prophylaxis and treatment of venous thrombosis and its extension;
• (In a low-dose regimen) for prevention of postoperative deep venous thrombosis and pulmonary embolism in patients undergoing major abdomino-thoracic surgery or who for other reasons are at risk of developing thromboembolic disease
• Prophylaxis and treatment of pulmonary embolism;
• Prophylaxis and treatment of peripheral arterial embolism.

Heparin is also used to associated treatment for these conditions: Blunt Injuries, Clotting, Coagulopathy, Consumption, Contusions, Disseminated Intravascular Coagulation (DIC), External Hemorrhoid, Inflammation, Inflammatory, non-infectious pruritic dermatosis, Interstitial Cystitis, Pulmonary Embolism, ST Elevation Myocardial Infarction (STEMI), Sprains, Thromboembolism, Thrombosis, Venous, Unstable Angina Pectoris, Venous Thromboembolism, Embolization, Hematomas, Peripheral arterial embolism, Varicosities of the great saphenous vein, Maintenance of patency of IV injection devices

How Heparin works

Under normal circumstances, antithrombin III (ATIII) inactivates thrombin (factor IIa) and factor Xa. This process occurs at a slow rate. Administered heparin binds reversibly to ATIII and leads to almost instantaneous inactivation of factors IIa and Xa The heparin-ATIII complex can also inactivate factors IX, XI, XII and plasmin. The mechanism of action of heparin is ATIII-dependent. It acts mainly by accelerating the rate of the neutralization of certain activated coagulation factors by antithrombin, but other mechanisms may also be involved. The antithrombotic effect of heparin is well correlated to the inhibition of factor Xa. Heparin is not a thrombolytic or fibrinolytic. It prevents progression of existing clots by inhibiting further clotting. The lysis of existing clots relies on endogenous thrombolytics.

Dosage

Heparin dosage

Intravenous-Prophylaxis of re-occlusion of the coronary arteries following thrombolytic therapy in myocardial infarction

• Adult: 60 U/kg (max: 4,000 U) or a bolus of 5,000 U if streptokinase was used, followed by 12 U/kg/hr (max: 1,000 U/hr) w/ a treatment duration of 48 hr.

Intravenous-

Peripheral arterial embolism, Unstable angina, Venous thromboembolism

• Adult: 75-80 U/kg or 5,000 U (10,000 U in severe pulmonary embolism) IV loading dose followed by 18 U/kg or 1,000-2,000 U/hr continuous infusion. Alternatively, intermittent inj of 5,000-10,000 U 4-6 hrly.
• Child: 50 U/kg loading dose, followed by an infusion of 15-25 U/kg/hr.
• Elderly: Lower dosages may be required.

Subcutaneous-

Prophylaxis of postoperative venous thromboembolism

• Adult: 5,000 U given 2 hr before surgery then 8-12 hrly for 7 days or until the patient is ambulant.

Subcutaneous-

Venous thromboembolism

• Adult: 15,000-20,000 U 12 hrly or 8,000-10,000 U 8 hrly.
• Child: 250 U/kg bid.
• Elderly: Lower dosages may be required.

Side Effects

Hypersensitivity reactions (e.g. chills, fever, urticaria, asthma, rhinitis); painful, ischaemic and cyanosed limbs; osteoporosis (in long-term admin), suppression of aldosterone synthesis leading to hyperkalaemia, cutaneous necrosis, delayed transient alopecia, priapism, rebound hyperlipaemia; increased serum concentrations of AST and ALT, prolonged prothrombin time; local irritation, erythema, mild pain, haematoma or ulceration on inj site.

Toxicity

In mouse, the median lethal dose is greater than 5000 mg/kg. Another side effect is heparin-induced thrombocytopenia (HIT syndrome). Platelet counts usually do not fall until between days 5 and 12 of heparin therapy. HIT is caused by an immunological reaction that makes platelets form clots within the blood vessels, thereby using up coagulation factors. It can progress to thrombotic complications such as arterial thrombosis, gangrene, stroke, myocardial infarction and disseminated intravascular coagulation. Symptoms of overdose may show excessive prolongation of aPTT or by bleeding, which may be internal or external, major or minor. Therapeutic doses of heparin give for at least 4 months have been associated with osteoporosis and spontaneous vertebral fractures. Osteoporosis may be reversible once heparin is discontinued. Although a causal relationship has not been established, administration of injections preserved with benzyl alcohol has been associated with toxicity in neonates. Toxicity appears to have resulted from administration of large amounts (i.e., about 100–400 mg/kg daily) of benzyl alcohol in these neonates. Its use is principally associated with the use of bacteriostatic 0.9% sodium chloride intravascular flush or endotracheal tube lavage solutions.

Precaution

Patient with increased risk of bleeding complications, HTN, DM, pre-existing metabolic acidosis. Do not use in catheter lock flushing. Hepatic and renal impairment. Elderly. Pregnancy and lactation.

Interaction

Enhanced anticoagulant effect with other drugs affecting platelet function or the coagulation system (e.g. platelet aggregation inhibitors, thrombolytic agents, salicylates, NSAIDs, vit K antagonists, dextrans, activated protein C). Decreased anticoagulant effect with gyceryl trinitrate infusion. Increased risk of hyperkalaemia with ACE inhibitors or angiotensin II antagonists.

Food Interaction

• Administer calcium supplement. This drug decreases calcium levels.
• Avoid herbs and supplements with anticoagulant/antiplatelet activity. Examples include garlic, ginger, bilberry, danshen, piracetam, and ginkgo biloba.

Heparin Hypertension interaction

[Major] Heparin should be used with extreme caution in patients with uncontrolled or severe hypertension as these conditions may predispose the patient to hemorrhage during heparin administration.

Blood coagulation tests (e.g., whole blood clotting time, activated partial thromboplastin time) should be performed at appropriate intervals during full-dose heparin administration.

In addition, periodic platelet counts, hematocrits, and tests for occult blood in stool are recommended during the entire course of heparin therapy.

Clinical monitoring of blood pressure is recommended.

Heparin Drug Interaction

Major: warfarin, warfarin, enoxaparin, enoxaparinMinor: clopidogrel, clopidogrelUnknown: furosemide, furosemide, sodium chloride, sodium chloride, acetaminophen, acetaminophen, acetaminophen, acetaminophen, cyanocobalamin, cyanocobalamin, cholecalciferol, cholecalciferol, ondansetron, ondansetron

Heparin Disease Interaction

Major: peptic ulcer disease, active bleeding, hypertension, prematurity, renal dysfunction, thrombocytopeniaModerate: hyperkalemia

Volume of Distribution

40-70 mL/min (approximately the same as blood volume) Although heparin does not distribute into adipose tissues, clinicians should use actual body weight in obese patients to account for extra vasculature.

Elimination Route

Heparin must be given parenterally as it is not absorbed through the gastrointestinal mucosa. It is usually given by iv infusion or deep sc injection. The onset of action is immediate after iv injection but can be delayed 20 to 60 minutes following sc injection.

Plasma heparin concentrations may be increased and activated partial thromboplastin times (aPTTs) may be more prolonged in geriatric adults (older than 60 years of age) compared with younger adults.

Half Life

1.5 hours.

The plasma half-life of heparin increases from about 60 minutes with a 100 unit/kg dose to about 150 minutes with a 400 unit/kg dose.

Clearance

Adult Clearance = 0.43 ml/kg/min 25-28 weeks gestation = 1.49 ml/kg/min

Elimination Route

The drug appears to be removed mainly by the reticuloendothelial system. A small fraction of unchanged heparin also appears to be excreted in urine. Heparin cannot be eliminated by hemodialysis.

Pregnancy & Breastfeeding use

Pregnancy Category C. Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Nursing Mothers: Due to its large molecular weight, heparin is not likely to be excreted in human milk, and any heparin in milk would not be orally absorbed by a nursing infant. Benzyl alcohol present in maternal serum is likely to cross into human milk and may be orally absorbed by a nursing infant. Exercise caution when administering Heparin Sodium Injection to a nursing mother.

Contraindication

Current or history of heparin-induced thrombocytopenia; generalised or local haemorrhagic tendency, including uncontrolled severe HTN, severe liver insufficiency, active peptic ulcer, acute or subacute septic endocarditis, intracranial haemorrhage or injuries and operations on the CNS, eyes and ears, and in women with abortus imminens; epidural anaesth during birth; locoregional anaesth in elective surgical procedures (in patients receiving heparin for treatment rather than prophylaxis).

Special Warning

Pediatric Use: There are no adequate and well controlled studies on heparin use in pediatric patients. Pediatric dosing recommendations are based on clinical experience. Carefully examine all Heparin Sodium Injection vials to confirm choice of the correct strength prior to administration of the drug. Pediatric patients, including neonates, have died as a result of medication errors in which vials have been confused with “catheter lock flush” vials

Acute Overdose

Symptoms: Bleeding (nose bleeds, blood in urine or tarry stools may be noted as the 1st sign of bleeding).

Management: May give protamine sulfate by slow IV infusion over 10 min to treat severe bleeding (1 mg of protamine sulfate neutralises approx 100 U of heparin). Max: 50 mg as a single dose.

Storage Condition

Store between 20-25° C. Protect from freezing.

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