BMA Concise Guide to Medicine & Drugs

Heparin/Low Molecular Weight Heparins

Brand names Calciparine, Monoparin, Multiparin; [LMWH] Clexane, Clivarine, Fragmin, Innohep, Zibor

Used in the following combined preparations None


Drug group Anticoagulant drug

Overdose danger rating High

Dependence rating Low

Prescription needed Yes

Available as generic Yes (heparin); No (LMWH)


Heparin is an anticoagulant drug used to prevent formation of, and aid in dispersion of, blood clots. Because the drug acts quickly, it is particularly useful in emergencies to prevent further clotting when a clot has already reached the lungs or the brain, for instance. People undergoing open heart surgery or kidney dialysis are also given heparin to prevent clotting. A low dose is sometimes given following surgery to prevent the development of deep vein thrombosis (clots in the leg veins). Heparin is often given in conjunction with other slower acting anticoagulants, such as warfarin. It is also used to treat unstable angina.

The most serious adverse effect, as with all anticoagulants, is excessive bleeding, so the blood’s clotting ability is watched very carefully. Bruising may occur around the injection site.

Several types of heparin known as low molecular weight heparins (LMWH) do not have to be administered in hospital.


This drug is given only under medical supervision and is not for self-administration.

How taken/used Injection, intravenous infusion.

Frequency and timing of doses Every 8–12 hours or continuous intravenous infusion; once daily (LMWH).

Dosage range Dosage is determined by the nature of the condition being treated or prevented.

Onset of effect Within 15 minutes.

Duration of action 4–12 hours after treatment is stopped; 24 hours after end of treatment (LMWH).

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Notify your doctor.

Stopping the drug Do not stop taking the drug without consulting your doctor. Stopping the drug may lead to clotting of blood.


Seek immediate medical advice in all cases. Take emergency action if bleeding, severe headache, or loss of consciousness occur.


Bleeding is the most common adverse effect, and the risk of it occurring is increased in people with impaired kidney function. Bruising is also common. You should inform your doctor immediately if either occur. Less common side effects include hair loss, aching bones, breathing difficulties, jaundice, vomiting blood, and rash. Consult your doctor if hair loss or aching bones occur. If you develop breathing difficulties, rash, jaundice, or vomit blood, you should contact your doctor immediately; the drug should also be stopped if you develop a rash.


Aspirin and other NSAIDs may increase the anticoagulant effect of heparin and the risk of bleeding in the intestines or joints. Do not take these drugs with heparin.

ACE inhibitors and potassium supplements taken with heparins may increase the risk of high blood potassium.

Clopidogrel, ticlopidine, and dipyridamole The anticoagulant effect of heparin may be increased when it is taken with these drugs. The dosage of heparin may need to be adjusted accordingly.


Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have high blood pressure.

· You bleed easily or are currently bleeding.

· You have any allergies.

· You have peptic ulcers.

· You have diabetes.

· You have had a previous reaction to heparin.

· You have had a recent stroke, injury, or surgery.

· You are taking other medicines.

Pregnancy Careful monitoring is necessary as it may cause the mother to bleed excessively if taken near delivery. Discuss with your doctor.

Breast-feeding No evidence of risk.

Infants and children Reduced dose necessary according to age and weight.

Over 60 No special problems, but the elderly may be more prone to bleeding.

Driving and hazardous work Avoid risk of injury, since excessive bruising and bleeding may occur.

Alcohol No special problems.

Surgery and general anaesthetics Heparin may need to be stopped. Discuss this with your doctor or dentist before having any surgery.


Osteoporosis and hair loss may occur very rarely with long-term use; tolerance to heparin may also develop.

Monitoring Periodic blood and liver function tests will be required.