Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Of particular concern to individuals taking decongestants are:

• Beta blockers. Drugs that help to control blood pressure by interfering with epinephrine (hormone used to increase blood pressure). Decongestants can interfere with these medicines, reducing their effectiveness and increasing the chance of side effects.
  
  
• Monoamine oxidase (MAO) inhibitors. These drugs are frequently used to slow the breakdown of certain neurotransmitters (often to treat depression). Using a decongestant within two weeks of a MAO inhibitor can increase the risk of serious side effects.
  
  
• Cocaine. Using cocaine and decongestants together can interfere with the heart, potentially causing irregularities. Their combined use also increases the chance of side effects developing.
  
  
• Caffeine. Using caffeine with a decongestant can cause some of the side effects of decongestants (e.g., heart palpitations, tremors) to worsen.
  
  
• Diet pills. Taking diet pills with a decongestant can increase stimulation of the central nervous system and other side effects of the diet aids.