Antifibrinolytics

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Chapter: Essential pharmacology : Drugs Affecting Coagulation, Bleeding And Thrombosis

These are drugs which inhibit plasminogen activation and dissolution of clot.


ANTIFIBRINOLYTICS

 

These are drugs which inhibit plasminogen activation and dissolution of clot.

 

Epsilon Aminocaproic Acid (EACA)

 

It is an analogue of the amino acid lysine: combines with the lysine binding sites of plasminogen and plasmin so that the latter is not able to bind to fibrin and lyse it. It is a specific antidote for fibrinolytic agents and has been used in many hyper-plasminaemic states associated with excessive intravascular fibrinolysis resulting in bleeding, e.g.:

 

·    Overdose of streptokinase/urokinase/alteplase.

·    To prevent recurrence of subarachnoid and g.i. haemorrhage.

· Certain traumatic and surgical bleedings (prostatectomy, tooth extraction in haemophiliacs).

·     Abruptio placentae, PPH and certain cases of menorrhagia.

 

However, the usefulness of EACA in most of the above conditions is equivocal, except in overdose of fibrinolytics. In haematuria it can cause ureteric obstruction by the unlysed clots. Therefore, fibrinolysis must be established firmly before using it. It can cause intravascular thrombosis. Rapid i.v. injection results in hypotension, bradycardia and may be arrhythmias. It should be used cautiously when renal function is impaired. Myopathy occurs rarely.

 

Initial priming dose is 5 g oral/i.v., followed by 1 g hourly till bleeding stops (max. 30 g in 24 hrs).

 

AMICAR, HEMOCID, HAMOSTAT 0.5 g tab., 1.25 g/5 ml syr., 5 g/20 ml inj.

 

Tranexaemic Acid

 

Like EACA, it binds to the lysine binding site on plasminogen and prevents its combination with fibrin and is 7 times more potent. It has been used for prevention of excessive bleeding in:

 

·      Overdose of fibrinolytics

·      After cardiopulmonary bypass surgery.

·      After tonsillectomy, prostatic surgery, tooth extraction in haemophiliacs.

·      Menorrhagia, specially due to IUCD.

·      Recurrent epistaxis, ocular trauma, bleeding peptic ulcer.

 

Main side effects are nausea and diarrhoea. Headache, giddiness and thrombophlebitis of injected vein are other adverse effects.

 

Dose: 10–15 mg/kg 2–3 times a day or 1–1.5 g TDS oral, 0.5–1 g TDS by slow i.v. infusion.

 

CYCLOKAPRON 500 mg tab, 100 mg/ml inj.

 

Aprotinin

 

It is a polypeptide isolated from bovine tissues with polyvalent serine protease inhibitory activity: trypsin, chymotrypsin, kallikrein and plasmin are inhibited. It can be administered only i.v. and has a t½ of 2 hr. It has been employed in selected situations:

Administered at the beginning of cardiopulmonary bypass surgery—it reduces blood loss.

Traumatic, haemorrhagic and endotoxic shock—has adjuvant value.

Acute pancreatitis (trypsin may be released in circulation which may be fatal).

Fibrinolytic states, prostatic surgery, carcinoid: may afford symptomatic relief.

Renal toxicity and ischaemic events like MI and stroke are the possible adverse effects.

 

Dose: 5 lac KIU (Kallikrein inactivator unit) initially, followed by 2 lac KIU every 4 hr, all as slow i.v. infusion; TRASYLOL INF 5 lac KIU in 50 ml inj; APROGEN 1 lac KIU (10 ml) and 5 lac KIU (50 ml) inj.

 

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