Heparin Sodium 肝素
Translated and edited by Joe Hing Kwok Chu
Heparin is so called because it is was first obtained from livers. Heparin is normally found in the body. It is a mixture of sulfate-containing mucopolyaccharides with a strong acid reaction and a large electronegative charge. Today the pharmaceutical product is mainly extracted from livers of pigs, cattle, sheep and lungs of cattle. The dried product of one mg should not contain less than 140 units of heparin.
Characteristics: It is a white or nearly white powder. It attracts moisture easily and dissolves in water easily. Its water solution carries strong negative ions.
Medical functions: Used in anti blood clotting. It has anticoagulation properties either inside or outside the body. It can prolong coagulation time, and action of thrombin (enzyme of coagulation), and action of factor II (prothrombin). Today, it is deemed that the anti-coagulation effect is achieved through the function of anti thrombin III (AT III) . AT III is a kind of plasma alpha globulin that acts like a factor in assisting heparin sodium and can combine with many coagulation factors and inhibit the action of these factors thus affecting the many functions of the coagulation process: (1) suppressing the activities of factors XII, XI, IX, X, II and VIII; (2) combining with factor II; (3) neutralizing factor III in the tissues. The combining of heparin sodium and AT III accelerates the anti coagulation function of AT III.
When used intravenously, heparin should be first given as a loading dose with a bolus of 5000 units.
(1) Intravenous: adult dosage 5000 units with added 100 ml 5~10% glucose solution or 0.9% sodium chloride solution. Application speed: 20~30 drops per minute to be completed within 30~60 minutes. When necessary, repeat every 4~6 hours with 5000 units each and total application can be 25,000 units per day. To maintain a constant ratio of blood and heparin, in a 24 hour period, 10,000~20,000 units with added 1000 ml 5% glucose solution or 0.9% of sodium chloride can be used in intravenous application of 20 drops per minute. When used in external circulation, use 375 units per kg of body weight. Use 125 units per kg of body weight if used longer than an hour.
(2) Deep muscle or subcutaneous injection: 10,000 ~12,500 units every 8~12 hours.
No data to suggest that the dose has to be adjusted for the elderly.
Warning: (1) Over usage of heparin causes idiopathic bleeding. Symptoms: mucus bleeding (blood in urine, bleeding in the digestive track), bleeding in the joints, and bleeding of wounds. While using Heparin, tests of Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) should be performed. APTT should be performed at 6 hours, with subsequent heparin infusion rates adjusted to achieve an APTT that is 1.5~2.5 times the mean pretreatment or control value(1). If the APTT is >30 minutes or the PT is >100 seconds, it means an over dosage of heparin; stop application. Stop using heparin immediately if there is any sign of idiopathic bleeding. In case of serious bleeding protamine can be used as an antidote. (2) The use of intravenous application of protamine for neutralizing heparin sodium should not exceed 20 mg per minute. It is recommended that 50 mg to be administered in a period of 10 minutes. Normally every one mg of protamine inside the body can neutralize 100 units of heparin sodium.
(2) Sometimes it can cause allergic reactions like asthma attacks, hives, conjunctivitis and fever. Prolonged usage can cause hair loss or temporary (reversible) baldness, osteoporosis, and idiopathic bone breaks and temporary platelet decrease.
(3) Do not use heparin sodium if there is allergic reaction, tendency of bleeding, low platelet counts, hemophilia, peptic ulcer, serious hypertension, intracranial bleeding, endocarditis of bacteria infection, active tuberculosis, symptoms of miscarriage, recently after giving birth, tumor of internal organ, external open wound injury or post surgery. Do not use during pregnancy unless it can be accurately determined that there is no reaction.
(4) Muscle or skin injections of heparin sodium can cause strong irritation. Using thinner needles at the location of deep muscle or subcutaneous fatty tissue is recommended.
Dosage: injection liquid: 1000 units (2 ml), 5000 units (2ml), 12,500 units (2ml)
(1)Hirsh J. Heparin. New England Journ. Med. 1991;324;1565 - 1574
(2) Chen Xin Qian, Jin You Yu et al , New Edition of Pharmacology, 1996; 340 新编藥物學，陳新謙，金有豫 主编