Premedication
To avoid or limit adverse reactions caused by a procedure, many patients are treated with drugs known to treat or prevent such reactions. In connection with imaging and angioplasty procedures there are particularly 2 distinct situations where premedication is used. 1 To avoid clotting and emboli caused by the procedure and/or equipment used, it is common to pretreat patients before PTCA and complex angiographies with some anticoagulant, e.g. acetylsalicylic acid ("aspirin") to block platelet aggregation and heparin before the procedure. For heparin it is important to realise that the effect varies between patients. Laboratory testing is necessary to ensure adequate protection throughout the procedure. Sometimes another anticoagulant drug is used, e.g. warfarin. Warfarin needs 3-4 days to reach sufficient anticoagulant protection, and adequate control is necessary. Warfarin pretreatment should not be combined with acetylsalicylic acid. Over the last years several new anticoagulant drugs (e.g. abciximab) have been marketed, and, although not available in all countries yet, these have largely replaced Heparin and Warfarin. Although all contrast media have some effect on coagulation, this effect is far too weak to give any protection against clotting/emboli alone ! 2 – To avoid hypersensitivity ("allergy-like") reactions to contrast media, drugs used to treat allergies (anti-histamines and corticosteroids) are often used. Although they may have some effect in light to moderate reactions, these drugs have little or no effect on serious, potentially life-threatening reactions, and may actually mask early symptoms of such reactions. Since such reactions are both more frequent and serious with high-osmolar ionic contrast media, it is recommended to use non-ionic low-osmolar or isosmolar contrast media, although some (usually light) hypersenstitivity reactions may be seen with these too.
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