Description

frequent occurrence of hematoma at the injection site. 
The dosage of heparin sodium should be adjusted according to the patient’s coagulation test results. 
When heparin is given by continuous intravenous infusion, the coagulation time should be determined 
approximately every 4 hours in the early stages of treatment. When the drug is administered 
intermittently by intravenous injection, coagulation tests should be performed before each injection 
during the early stages of treatment and at appropriate intervals thereafter. 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. 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, hematocrits and tests for occult blood in stool are recommended during the 
entire course of heparin therapy, regardless of the route of administration. 
Converting to Oral Anticoagulant 
When an oral anticoagulant of the coumarin or similar type is to be begun in patients already receiving 
heparin sodium, baseline and subsequent tests of prothrombin activity must be determined at a time 
when heparin activity is too low to affect the prothrombin time. This is about 5 hours after the last 
intravenous bolus and 24 hours after the last subcutaneous dose. If continuous IV heparin infusion is 
used, prothrombin time can usually be measured at any time. 
In converting from heparin to an oral anticoagulant, the dose of the oral anticoagulant should be the 
usual initial amount and thereafter prothrombin time should be determined at the usual intervals. To 
ensure continuous anticoagulation, it is advisable to continue full heparin therapy for several days after 
the prothrombin time has reached the therapeutic range. Heparin therapy may then be discontinued 
without tapering. 
 

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NDA 17-037/S-158 
Page 10