Three groups of drugs are used to reduce the stickiness of platelets, thus preventing platelets from clumping together to form platelet plugs. The anti-platelet drugs are most effective in preventing abnormal blood clots from forming in arteries (as opposed to veins). Aspirin and dipyridamoleâ (Aggrenox).
In order to react, colliding molecules must have a total kinetic energy equal to or greater than some minimum value [Figure 14.13(b)]. The minimum energy required to initiate a chemical reaction is called the activation energy, Ea. The value of Ea varies from reaction to reaction.
First of all, for a reaction to occur, the colliding molecules must be oriented in exactly the correct way: they must be oriented in suitable way for the product molecule bonds to be formed. Second, the two molecules must collide with sufficient energy to overcome the activation energy of the reaction. The activation energy is defined as the minimum energy needed to initiate a chemical reaction, and it is symbolized by E a.