McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 8 Drugs affecting blood coagulation

DRUGS USED TO CONTROL BLEEDING On the other end of the spectrum of coagulation problems are various bleeding disorders. These include the following: • Haemophilia , in which there is a genetic lack of clotting factors that leaves the person vulnerable to excessive bleeding with any injury. • Liver disease , in which clotting factors and proteins needed for clotting are not produced. • Bone marrow disorders , in which platelets are not formed in sufficient quantity to be effective. Bleeding disorders are treated with clotting factors and drugs that promote the coagulation process. These include antihaemophilic agents and haemostatic agents (systemic and topical). (See Table 48.4.) A ntihaemophilic agents The drugs used to treat haemophilia are replacement factors for the specific clotting factors that are geneti­ cally missing in that particular type of haemophilia. These drugs include antihaemophilic factor, recombi­ nant ( Recombinate [not available in New Zealand]), coagulation factor VIII ( Biostate [not available In New Zealand]) and factor IX complex ( MonoFIX-VF ).

Haemorheologic agent Oxpentifylline ( Trental ) is known as a haemorrheologic agent, or a drug that can induce haemorrhage. It is a xanthine that, like caffeine and theophylline, decreases platelet aggregation and fibrinogen concentration in the blood. These effects can decrease blood clot formation and increase blood flow through narrowed or damaged vessels. The mechanism of action by which oxpentifyl­ line does these things is not known. It is one of the very few drugs found to be effective in treating intermittent claudication, a painful vascular problem of the legs. Because oxpentifylline is a xanthine, it is associated with many cardiovascular stimulatory effects; people with underlying cardiovascular problems need to be monitored carefully when taking this drug. Oxpenti­ fylline can also cause headache, dizziness, nausea and upset stomach. It is taken orally three times a day for at least 8 weeks to evaluate its effectiveness. See Table 48.1 for additional information about this drug.

KEY POINTS

■■ To keep blood from coagulating, anticoagulants block blood aggregates or interfere with the mechanisms that cause blood to clot. ■■ Thrombolytic drugs activate the plasminogen system to dissolve clots naturally.

TABLE 48.4

DRUGS IN FOCUS Drugs used to control bleeding

Drug name

Dosage/route

Usual indications

Antihaemophilic agents Antihaemophilic factor, recombinant (Recombinate)

IV dose based on serum factor VIII levels and body weight

Prevention and control of bleeding episodes in haemophilia A; perioperative management of bleeding in people with haemophilia A Treatment of bleeding episodes in people with haemophilia A or B Treatment or prevention of haemophilia B (Christmas disease, a deficiency of factor IX); treatment of bleeding episodes in people with factor VII and factor VIII deficiencies; controls bleeding episodes in people with haemophilia A

coagulation factor VIIa (NovoSeven)

90 mcg/kg IV q 2 hours until haemostasis is achieved IV dose based on factor levels, weight and desired response

factor IX complex (MonoFIX-VF)

Haemostatic agents Topical absorbable gelatin (Gelfoam) human fibrin sealant (Artiss, Tisseel)

Smear or press onto surface; do not remove, will be absorbed

Controls bleeding from surface cuts or injury Adheres autologous skin grafts to surgically prepared wound beds resulting from burns in adults and children

Apply thin layer on to site