The relative risks and benefits of heparin should be carefully assessed in patients with a bleeding tendency or those patients with an actual or potential bleeding site e.g. hiatus hernia, peptic ulcer, neoplasm, bacterial endocarditis, retinopathy, bleeding haemorrhoids, suspected intracranial haemorrhage, cerebral thrombosis or. Care should also be taken when heparin is administered to patients with hypertension, renal or hepatic insufficiency.
Platelet counts should be measured in patients receiving heparin treatment for longer than 5 days and the treatment should be stopped immediately in those who develop thrombocytopenia. Heparin induced thrombocytopenia (HIT) and heparin induced thrombocytopenia with thrombosis (HITT) can occur up to several weeks after discontinuation of heparin therapy. Patients presenting with thrombocytopenia or thrombosis after discontinuation of heparin should be evaluated for HIT or HIT. In patients with advanced renal or hepatic disease, a reduction in dosage may be necessary. The risk of bleeding is increased with severe renal impairment and in the elderly (particularly elderly women).
Although heparin hypersensitivity is rare, it is advisable to give a trial dose of 1,000 I.U. in patients with a history of allergy. Heparin should be used with caution in patients with hypersensitivity to low molecular weight heparins.
In most patients, the recommended low-dose regimen produces no alteration in clotting time. However, patients show an individual response to heparin, and it is therefore essential that the effect of therapy on coagulation time should be monitored in patients undergoing major surgery.
Caution is recommended in patients receiving heparin prophylactically and undergoing spinal or epidural anaesthesia or spinal puncture (risk of spinal or epidural haematoma resulting in prolonged or permanent paralysis). The risk is increased by the use of a peridural or spinal catheter for anaesthesia, by the concomitant use of drugs affecting haemostasis such as non-steroidal anti-inflammatory drugs (NSAIDs), platelet inhibitors or anticoagulants and by traumatic or repeated puncture. In decision making on the interval between the last administration of heparin at prophylactic doses and the placement or removal of a peridural or spinal catheter, the product characteristics and the patient profile should be taken into account. Subsequent dose should not take place before at least four hours have elapsed. Re- administration should be delayed until the surgical procedure is completed.
In patients receiving heparin for treatment rather than prophylaxis, locoregional anaesthesia in elective surgical procedures is contra- indicated because the use of heparin may be very rarely associated with epidural or spinal haematoma resulting in prolonged or permanent paralysis. If such a procedure is planned the heparin should be stopped and the procedure should be delayed until the aPTT has returned to normal.
Should a physician decide to administer anti-coagulation in the context of peridural or spinal anaesthesia, extreme vigilance and frequent monitoring must be exercised to detect any signs and symptoms of neurologic impairment, such as back pain, sensory and motor deficits and bowel or bladder dysfunction. Patients should be instructed to inform immediately a nurse or a clinician if they experience any of these.
Heparin can suppress adrenal secretion of aldosterone leading to hyperkalaemia, particularly in patients such as those with diabetes mellitus, chronic renal failure, pre-existing metabolic acidosis, a raised plasma potassium, or taking potassium sparing drugs. The risk of hyperkalaemia appears to increase with duration of therapy but is usually reversible. Plasma potassium should be measured in patients at risk before starting heparin therapy and in all patients treated for more than 7 days.
Due to increased bleeding risk, care should be taken when giving concomitant intramuscular injections, lumbar puncture and similar procedures.
Heparin resistance
There is considerable variation in individual anticoagulant responses to heparin.
Heparin resistance, defined as an inadequate response to heparin at a standard dose for achieving a therapeutic goal occurs in approximately 5 to 30% of patients.
Factors predisposing to the development of heparin resistance include:
• Antithrombin III activity less than 60% of normal (antithrombin III- dependent heparin resistance):
Reduced antithrombin III activity may be hereditary or more commonly, acquired (secondary to preoperative heparin therapy in the main, chronic liver disease, nephrotic syndrome, cardiopulmonary bypass, low grade disseminated intravascular coagulation or drug induced, e.g. by aprotinin, oestrogen or possibly nitroglycerin)
• Patients with normal or supranormal antithrombin III levels (antithrombin III-independent heparin resistance)
| | ● | Thromboembolic disorders |
| | ● | Increased heparin clearance |
• Elevated levels of heparin binding proteins, factor VIII, von Willebrand factor, fibrinogen, platelet factor 4 or histidine- rich glycoprotein
| | ● | Active infection (sepsis or endocarditis) |
| | ● | Preoperative intra-aortic balloon counterpulsation |
| | ● | Thrombocytopenia |
| | ● | Thrombocytosis |
| | ● | Advanced age |
| | ● | Plasma albumin concentration ≤ 35g/dl |
| | ● | Relative hypovolaemia |
Heparin resistance is also often encountered in acutely ill patients, in patients with malignancy and during pregnancy or the post-partum period.
Drugs affecting platelet function or the coagulation system should in general not be given concomitantly with heparin (see section 4.5).
Excipients
Heparin contains methyl- and propyl parahydroxybenzoate and sodium as excipients. Methyl- and propyl parahydroxybenzoate may cause allergic reactions (possibly delayed), and exceptionally, bronchospasm.
Heparin sodium 5,000 IU/mL solution for injection or concentrate for solution for infusion
This medicine contains 34 mg sodium (main component of cooking/table salt) in each vial. This is equivalent to 1.7 % of the recommended maximum daily dietary intake of sodium for an adult.