Drug Interactions between conestat alfa and ethinyl estradiol / norelgestromin

MONITOR: Thromboembolism may occur during treatment with C1 esterase inhibitors, and concurrent use of other agents that are also associated with this adverse effect can potentiate the risk. Serious arterial and venous thromboembolic events, including myocardial infarction, deep vein thrombosis, pulmonary embolism, transient ischemic attack and stroke, have been reported with the use of plasma-derived C1 esterase inhibitor products at recommended dosages in patients with risk factors. A definitive causal relationship has not been established. Risk factors may include the presence of an indwelling venous catheter/access device, prior history of thrombosis, underlying atherosclerosis, morbid obesity, immobility, and concomitant use of medications such as oral contraceptives or certain androgens. Data from in vitro and in vivo animal thrombogenicity studies conducted with a plasma-derived C1 esterase inhibitor showed a potential for clot formation when administered at dosages 14 times the recommended clinical dose. Thrombotic events have been reported with another C1 esterase inhibitor product when used off-label at high dosages in newborns and young children with congenital heart anomalies during or after cardiac surgery.

MANAGEMENT: Caution is advised when C1 esterase inhibitors are used with other drugs that have thrombogenic effects such as androgens, estrogens, erythropoiesis- or thrombopoiesis-stimulating agents, or selective estrogen receptor modulators. Close monitoring for thromboembolic events is recommended during and after administration of C1 esterase inhibitors. Patients should be advised to seek medical attention if they develop potential signs and symptoms of thromboembolism such as chest pain; shortness of breath; rapid pulse; pain, swelling, and/or discoloration in an arm or leg; and numbness or weakness on one side of the body.