• Ethex is an over-the-counter medication that is also sold under the name Guaivent. It is a medication that combines two active drugs, guaifenesin and pseudoephedrine. Pseudoephedrine works as a decongestant to relieve relieve cold symptoms like a stuffy nose. Guaifenesin helps to loosen congestion and works as an expectorant. This cold medication can be used to treat symptoms from allergies, infections or a cold. Before using this medication, consider the possible side effects.
  
  

Side Effects

• You may experience some side effects when taking Ethex. Talk to your doctor if you experience dizziness, restlessness, excitability, headache, insomnia, vomiting, nausea, loss of appetite, stomach upset, skin rash, itching or tingling or warmth under your skin. According to Drugs.com, if you experience more serious side effects, you'll need medical help right away. These possible side effects can include severe headache, chest pain, numbness, blurred vision, seizures, severe dizziness, weakness, fever or flu symptoms, problems concentrating and a pounding or uneven heartbeat. Signs of a possible allergic reaction to Ethex can include hives, swelling of the facial region and difficulty breathing.
  
  

Interaction Warnings

• Do not combine Ethex with certain other medications, as you may experience a drug interaction. According to Drugs.com, medications that should not be taken with Ethex include high blood pressure drugs, beta-blockers, antidepressants, methyldopa, diet pills, caffeine pills, stimulants, any other cough or cold medication, allergy medications or ADHD drugs. Additionally, according to Med Help, you may experience serious side effects that are life-threatening if you use any cold medicine, including Ethex, within 14 days of taking an MAO inhibitor. Drinking alcohol while using Ethex may worsen side effects.
  
  

Pre-existing Conditions

• You may be unable to use Ethex if you have certain pre-existing medical conditions. Talk to your doctor about whether it's safe to use this drug if you have a thyroid disorder, diabetes, high blood pressure, heart disease or phenylketonuria (PKU). Drugs.com warns that you should not use this medication without your doctor's approval if you are pregnant, may become pregnant or if you are nursing an infant. Additionally, if you're planning to have surgery, you'll need to discuss your cold medicine and any other medication with your surgeon. Some medications may interfere with your body's ability to clot blood.