Blood drugs anticoagulants

Stoppers may contain zinc, invalidating the use of evacuated blood tubes for zinc measurement, and TBEP (tris[2-butoxyethyi] phosphate), a constituent of rubber, which may interfere with the measurement of certain drugs. With time, the vacuum in evacuated tubes is lost and their effective draw diminishes. The silicone coating also decays with age. Therefore the stock of these tubes should be rotated and careful attention paid to the expiration date. Problems with evacuated blood tubes also arise when too little blood is collected into the tubes (short draw). Although an incorrect draw is of little consequence when clotted blood is required, a disproportionate ratio of blood to anticoagulant may affect some hematology and other special tests. Therefore some tubes from each batch should be checked for volume of draw before the lot is put in use. 

Model I has been applied to a wide variety of drug responses, such as the reduction of fever (8, 20) or pain (19) by anti-inflammatory drugs, anticoagulant action of warfarin (3,9), reduction in blood sorbitol levels by inhibitors of aldose reductase (21), cortisol suppressive effects of corticosteroids (22), luteinizing hormone suppression by the synthetic hormone cetrorelix (23), reduction in the levels of tumoral phospho-EGFR (epidermal growth factor receptor) by cetuximab (24), inhibition of dihydrotestosterone (25), the suppression of T-lymphocyte influx into the blood by corticosteroids (26), and the acid-inhibitory effects of H2-receptor antagonists (27). 

The effects of oral hypoglycemic drugs, oral anticoagulants, and phenytoin may be increased when administered with chloramphenicol. Fhenobarbital or rifampin may decrease chloramphenicol blood levels. 

The most commonly used oral anticoagulant drug in the U.S. is warfarin. It acts by altering vitamin K so that it is unavailable to participate in synthesis of vitamin K-dependent coagulation factors in the liver (coagulation factors II, VII, IX, and X). Because of the presence of preformed clotting factors in the blood, the full antithrombotic effect of warfarin therapy may require 36 to 72 h. 

Reduction in blood pressure caused by treprostinil may be exacerbated by drugs that by themselves alter blood pressure, such as diuretics, antihypertensive agents, or vasodilators. Because treprostinil inhibits platelet aggregation, there is also a potential for increased risk of bleeding, particularly among patients maintained on anticoagulants. 

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