An elderly patient received a heparin injection (100IE/ml) to prevent clotting in an intravenous ca

Fråga: An elderly patient received a heparin injection (100IE/ml) to prevent clotting in an intravenous cannula. Directly after the heparin injection the patient experienced an anaphylactoid reaction with tickling in the lips, shortness of breath and affected general condition. After an immediate adrenaline injection the patient rapidly improved. Could Fragmin (low-molecular-weight heparin) be given to this patient?

Sammanfattning: Hypersensitivity reactions to high-molecular-weight heparin are well known but rare. Anaphylactic reactions have been reported. Low-molecular-weight heparin carries a lower risk for allergic reactions but cross-reactions do occur. In the present case, an avoidance of treatment with heparins is recommended as the risk of a new anaphylactic reaction cannot be excluded.

Svar: Hypersensitivity reactions to heparin are well known but rare (1,2,3). A wide range of symptoms has been described including urticaria, conjunctivitis, rhinitis, asthma, cyanosis, tachypnoea, fever, angioneurotic oedema and anaphylactic shock.

Six cases of anaphylactic reactions and two cases of anaphylactic shock have been reported to SADRAC (Swedish Adverse Drug Reactions Committee) all with a probable or possible casual relation to high-molecular-weight heparin administration.

In patients who develop thrombocytopaenia, the administration of high-molecular-weight heparin should be stopped immediately,and after an in vitro platelet aggregation test of immunological cross-reaction has been performed, the treatment can be continued with a low-molecular-weight heparin (5).

Adverse effects that have been reported rarely for some low-molecular-weight heparins include hypersensitivity reactions, thrombocytopaenia and skin necrosis at the site of injection (5).

SADRAC has not received any reports of anaphylactic reactions in connection with low-molecular-weight heparin, but these compounds have so far only had a limited use in Sweden.

If heparin has to be used as an anticoagulant therapy a low-molecular-weight heparin could be tried, with all precautions available, but the risk of a new hypersensitive reaction in a patient who has already reacted to ahigh-molecular-weight heparin cannot be excluded (6).

Orgaran, a drug recently registered by Organon, has the same therapeutic indications as heparin. The drug, also called Org-10172, is a low-molecular-weight heparinoid derived from porcine mucosa. It contains heparin sulphate, dermatan sulphate and chondroitin sulphate. This drug is not yet available on the market. In patients who have experienced a hypersensitivity reaction such as thrombocytopaenia after use of high-molecular-weight heparin there is a 10 per cent risk of the same reaction when Orgaran is used and a 30 per cent risk when a low-molecular-weight heparin is used (in vitro studies)(7).

Another drug called ancrod, a defibrinogenating enzyme derived from a snake venom with a clinical effect comparable to that of heparin, has been used in patients with acute thrombosis and heparin-induced thrombocytopaenia. Some authors believe that as it is not an heparinoid drug ancrod might be a suitable alternative (8). This drug is not on the market in Sweden.

We recommend that the present case be reported to SADRAC.