ese drugs, administered intravenously in hospital, are useful in the short term for certain patients undergoing coronary angioplasty or stenting—procedures to secure blood ow through arteries supplying the heart—and in some cases of acute coronary syndrome.

In Workbook 3, our patient Brian has a heart attack (MI). One possibility for immediate treatment is that the patient is ‘thrombolysed’, which means that a drug is given that will break down the clot that has blocked an artery serving part of his heart. is treatment will encourage the digestion of the brin mesh of the clot, and so is called a brinolytic or a thrombolytic. Figure 4.3 illustrates the native brinolytic system, whereby clots are broken down and removed. As also indicated in this gure, brinolytic drugs promote the conversion of brin-bound plasminogen to the proteolytic enzyme plasmin, which digests the brin mesh of the thrombus. Streptokinase is a bacterial protein which is administered by intravenous infusion and directly cleaves plasminogen to plasmin. Use of streptokinase, though, is limited because the patient develops antibodies which appear within a few days of administration, and which bind and inactivate the streptokinase. Presence of antibodies, which have been detected after prolonged periods of up to a year, can give rise to an anaphylactoid response if the drug is re­administered. For this reason streptokinase is rarely given again after 4 days of the initial treatment.