Patients should consult with their physician before taking antiplatelets. This is particularly important if an individual is allergic to aspirin or other analgesics. Also, antiplatelets may not be recommended if any of the following conditions apply:

• Impending surgery. Individuals who plan to undergo any surgical procedure requiring local, general or spinal anesthesia (including dental surgery) within two to three weeks. Surgery always carries the risk of uncontrolled and excessive bleeding, and antiplatelet medication could seriously increase that risk.
  
  
• Bleeding disorders. Antiplatelet medication could cause uncontrolled bleeding.
  
  
• Liver or kidney disease.
  
  
• Vitamin K deficiency (rare). Vitamin K is necessary to the natural formation of blood clots. Use of antiplatelet medication could potentially lead to uncontrolled bleeding.
  
  
• History of gastrointestinal bleeding or other bleeding problem.
  
  
• Thrombotic thrombocytopenic purpura (TTP). A rare, life-threatening blood disorder in which platelets are destroyed by antibodies. Antiplatelet medication could potentially lead to uncontrolled bleeding.

In addition, antiplatelets may make the following conditions worse:

• Anemia. A reduced number and or mass of red blood cells.
  
  
• Overactive thyroid. Overproduction of hormones by the thyroid gland, located in the front of the neck.
  
  
• Stomach ulcer. An open sore or crater in the stomach lining.

Side effects from antiplatelets may be increased in patients with the following conditions:

• High blood pressure (hypertension), which can increase the risk of bleeding into or around the brain
  
  
• Asthma
  
  
• Allergies
  
  
• Nasal polyps (or history of nasal polyps)