Decongestants can cause dangerous interactions with some medications and potentially complicate some health conditions. Patients should not take decongestants (even over-the-counter versions) unless they have consulted their physician. Patients should be particularly careful if they have been diagnosed with or are being treated for any of the following conditions:

• Asthma. Condition in which the airways become blocked or narrowed leading to breathing difficulties. Decongestants are never recommended for asthma treatment and can actually trigger an asthma attack in some individuals.
  

  

• Allergies to decongestants or other ephedrine-based products, as well as any other allergies (including other medications, food, pollen, dyes, etc.).
  
  
• Heart disease. Refers to many types of diseases or conditions of the heart, which usually result from an inadequate flow of blood to the heart muscle. The elevated blood pressure that sometimes results from decongestants can complicate this condition.
  
  
• Arrhythmias (abnormal heart rhythms). Decongestants can exacerbate this condition.
  
  
• Hypertension (high blood pressure). Because decongestants can lead to elevated blood pressure, hypertensive individuals should avoid the drugs when possible.
  
  
• Diabetes mellitus. Condition in which the body cannot adequately process glucose (blood sugar) for energy. Decongestants can cause an elevated blood glucose level, further complicating the condition.
  
  
• Enlarged prostate. Condition whereby the prostate grows large enough to press on the urethra and interfere with urination. Decongestants can cause individuals with this condition to have trouble urinating.
  
  
• Glaucoma. A group of diseases that affect the optic nerve, which connects the eye to the brain. The condition causes elevated pressure inside the eye. Decongestants can raise blood pressure, worsening this condition.
  
  
• Raynaud syndrome. A type of peripheral vascular disease in which spasms in the small arteries in the hands and feet cause a restriction in the flow of blood to the fingers and toes. As a result, the fingers and toes turn whitish, then cold, and eventually blue.
  
  
• Thyroid problems. Problems caused when the thyroid gland is producing too much (hyperthyroidism) or too little (hypothyroidism) of the hormones used to regulate the body’s metabolism. The use of decongestants can exacerbate these conditions.
  
  
• Kidney disease. The use of decongestants can increase the chance of side effects. Patients with kidney disease may require a different dose.