Heparins: Uses, common brands, and safety info

Heparins are a classic variety of anticoagulant therapy or blood thinner. The original heparin’s blood-thinning effects were discovered more than 100 years ago. In recent decades, new members of the heparin family have been discovered and expanded the ways in which this drug category can be used to treat and prevent life-threatening blood clots. These powerful medications are of great importance to health care but come with noteworthy risks. Use this guide to learn more about the uses of heparins, common varieties, their costs, and their side effects.

Other non-heparin anticoagulants

• Warfarin

• Eliquis

• Xarelto

• Pradaxa

• Plavix

• Brilinta

What are heparins?

Heparin is a polysaccharide (carbohydrate) molecule that is found naturally in the body. It was discovered to have anticoagulant activity in 1915. The forms of heparin that are used clinically derived from porcine (pig) or bovine (cow) sources and are available in intravenous or injectable forms, but not oral pills. Traditional unfractionated heparin (UFH) medication consists of a mix of many different molecular lengths and weights, while the newer low molecular weight heparins (LMWH) have shorter, lighter polysaccharide chains. Arixtra is made to mimic a portion of the heparin molecule.

How do heparins work?

The body works to maintain a balance between clotting when it needs to and not clotting when it is unnecessary. A blood clot is formed by a chain reaction of clotting factor enzymes that trigger one another. Anticoagulants block that series of enzymatic reactions at one or more points, effectively tipping the body’s balance toward dissolving clots rather than forming them. Thrombin and factor Xa are two important clotting factors that assist in clot formation, and heparins are effective blood thinners by inhibition of their actions. 

What are heparins used for?

• Venous thrombosis and thromboembolism (blood clot within the venous system)

• Arterial thrombosis and thromboembolism (blood clot within the arterial system)

• Deep vein thrombosis (DVT) (blood clot in the deep veins)

• Pulmonary embolism (blood clot in the lung)

• Myocardial infarction (heart attack)

• Coronary artery disease (blockages within the blood vessels supplying the heart)

• Atrial fibrillation (heart arrhythmia)

• Non-hemorrhagic stroke (stroke not related to bleeding in the brain)

• Transient ischemic attack (stroke symptoms without permanent brain tissue damage)

• Prevention of blood clots in individuals at higher risk, such as those with artificial heart valves, hospitalized patients, patients after joint replacements, individuals with genetic tendencies for excess blood clots, and those who have experienced serious blood clots in the past.

Types of heparins

Unfractionated heparin (UFH)

The blood-thinning effect of UFH relies on inhibiting both thrombin and factor Xa clotting factors. Administered both intravenously or via a shot under the skin, UFH has been a versatile blood thinner for many years. In hospitals, it is used to treat blood clots in a variety of clinical scenarios, as well as to prevent clots in at-risk patients. Low-dose heparin, in the form of catheter locks and flushes, is used to help keep intravenous catheters (IVs) from clotting shut. 

UFH has important differences compared to LMWH, and these differences can sometimes make it preferable. UFH starts to work almost immediately and has a short half-life, meaning it wears off fairly quickly. In addition, poor kidney function does not preclude its use.

Another advantage of UFH is the availability of an antidote to its action. If someone develops serious bleeding while on UFH, protamine sulfate can be administered to reverse the heparin action.

Unfortunately, intravenous heparin requires frequent blood monitoring to ensure the proper amount of blood thinning. The most common blood test used to monitor the effect of heparin is the activated partial thromboplastin time (aPTT), or less commonly, activated clotting time (ACT) or anti-factor Xa activity can be checked. Maintaining a therapeutic level of UFH activity without overdoing it can be difficult.

Low molecular weight heparin (LMWH)

The LMWHs Lovenox and Fragmin effectively thin the blood by inhibiting factor Xa. They are injected under the skin at regular intervals to maintain an anticoagulant effect. Both in the hospital and home settings, they are used to treat blood clots in numerous clinical situations, as well as for prophylaxis against clots.

They are slightly slower in the onset of action, but their longer duration of action permits intermittent injections for therapy rather than a continuous IV infusion like UFH. Kidney function is an important consideration with LMWH dosing, and poor kidney function may preclude their use.

LMWHs have an advantage over UFH by not requiring frequent blood tests to monitor effectiveness. Doses of heparin are based on weight typically. If necessary, anti-factor Xa activity can be checked to see the degree of anticoagulation with LMWH.

Arixtra

Arixtra is a synthetic molecule, made to match a small piece of heparin. It is able to inactivate the factor Xa clotting enzyme. Given as an intermittent injection under the skin, Arixtra is not used as often as UFH or LMWH, but it is still an important option for hospital and home-based treatment and prevention of blood clots. 

Arixtra is different enough molecularly from UFH and LMWH that it typically avoids the potentially life-threatening adverse effect of UFH and LMWH called heparin-induced thrombocytopenia (HIT). This complication occurs when heparins cause an immune reaction that leads to platelet (clotting cell) activation, causing clotting throughout the body and depletion of platelets. Arixtra can often be used by individuals with a history of HIT and can sometimes even be used to treat HIT. 

Who can take heparins?

Depending on the presence of other health conditions, men and women can both use heparins if the benefits of blood-thinning outweigh the risks of bleeding. Assessing for any ongoing bleeding, history of excess bleeding, and risk factors for excess bleeding is worthwhile before initiating heparin therapy.

Can you take heparins while pregnant or breastfeeding?

Heparin, Lovenox, and Fragmin can be used with caution in pregnancy and breastfeeding. Due to a paucity of clinical trials in pregnancy, Arixtra use is typically limited to individuals with an allergy to other heparins, and it is avoided in breastfeeding for the same reason.

Seniors

Seniors often need heparins because they experience a higher incidence of health conditions related to blood clots. Unfortunately, seniors are also at a higher risk of bleeding complications. More coinciding medications and health conditions for seniors are also concerns for older patients on heparin.

Children

Blood clots can occur within the pediatric population. UFH, LMWHs, and Arixtra can all be dosed for children based on their weight. However, some of the injectable options contain benzyl alcohol, and this is of particular concern for young children.

Are heparins safe?

Recalls

• Heparin compounded product recall (August 2020)

• Enoxaparin recall (February 2021)

Restrictions

• A black box warning from the FDA exists for Lovenox, Fragmin, and Arixtra regarding the risk of spinal hematoma (blood collection around the spine).

• People who have had hypersensitivity reactions to these products or related products should not take them again. A history of hypersensitivity to pork products can preclude UFH and LMWH use.

• Use of heparins is avoided in the setting of active major bleeding.

• Individuals with a history of heparin-induced thrombocytopenia (HIT) should not use UFH or Fragmin or often Lovenox due to the potential for recurrence of this life-threatening condition.

• Caution should be taken before using heparins if active bleeding, significant bleeding risk, severe high blood pressure, low platelet counts, or significant liver or kidney disease are ongoing, as well as in seniors, children, and pregnancy.

• Caution with or avoidance of anticoagulants including heparins is typical if one has had recent surgery, a spinal tap, or spinal anesthesia.

• Lovenox, Fragmin, and Arixtra also require caution if used in the settings of diabetic eye conditions and heart valve infections, as well as in both over and underweight individuals. 

• Latex allergy is a potential concern with Arixtra use.

Are heparins controlled substances?

Heparins are not controlled substances.

Common heparin side effects

• Bleeding

• Skin or tissue damage

• Rash

• Allergic reaction

• Liver damage

• Anemia or low platelet counts

• Low platelets with thrombosis (HIT or similar condition)

• Nausea, vomiting, or diarrhea

• Elevated potassium level

• Osteoporosis (thinning of the bones)

• Fever

• Newborn gasping with benzyl alcohol-containing injections

How much do heparins cost?

UFH is relatively inexpensive, but its use is most often limited to the hospital setting. The convenience of outpatient Lovenox, Fragmin, and Arixtra comes at a cost. Five days of treatment can amount to a retail expense of between $200 and $1,200. Fortunately, a SingleCare discount card can help with these costs.