PROTAMINE is a specific heparin antagonist that can be used to treat heparin-induced hemorrhage.

Warfarin, a vitamin K antagonist, is the oral anticoagulant of choice.

Administration of vitamin K can overcome the anticoagulant effects of the oral agents, but the effect takes about 24 hours.

There are a large number of drug interactions with the oral anticoagulants.

Direct thrombin inhibitors are also effective anticoagulants.

Anticoagulant and antiplatelet drugs are administered to prevent the formation or extension of clots. Thrombolytic drugs are used to lyse already formed clots.

The thrombolytic drugs are plasminogen activators.

Clot dissolution and reperfusion are more likely if therapy is initiated early after clot formation. Clots become more difficult to lyse as they age.

The main side effect of the thrombolytic drugs is bleeding.

STREPTOKINASE is a foreign protein and is antigenic. t-PA is not antigenic.

Phosphodiesterase III inhibitors (pentoxifylline and cilostazol) are used to treat intermittent claudication.

Iron salts, such as ferrous sulfate, are used as iron supplements to treat iron deficiency anemia.

Epoetin alfa and darbepoetin alfa are human recombinant erythropoietins.

Memantine is a noncompetitive antagonist at the NMDA subtype of glutamate receptor.

Tolerance is a physiological state characterized by a reduced drug effect with repeated use of the drug. Higher doses are needed to produce the same effect.

Cross-tolerance means that individuals tolerant to one drug will be tolerant to other drugs in the same class, but not to drugs in other classes.

Dependence is characterized by signs and symptoms of withdrawal when drug levels fall.

Cross-tolerance and cross-dependence occur between all of the CNS sedatives, includ- ing the barbiturates, benzodiazepines, and ethanol.

Barbiturates enhance the function of γ-aminobutyric acid (GABA) in the CNS.

Any other drug that is metabolized by the P-450 system will be altered by the presence of barbiturates.