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Generic name: guaifenesin and phenylephrine [gwye-FEN-e-sin-and-FEN-il-EFF-rin]

Brand names: Aldex G, Deconex IR, Despec, ED Bron GP, Gilphex TR,… show all 29 brands
Drug class: Combinations for the upper respiratory tract

What is Deconex?

Deconex, also known as a combination drug, is used to treat allergies in both adults and children. It treats symptoms like a runny, stuffy, or itchy nose or throat, mucusy cough, sinus pain, and chest congestion due to the cold or other allergies. This leaflet does not list all the brands or forms available of guaifenesin and phenylephrine. Deconex can also be used in other ways not mentioned in the medication guide.

Side effects of Deconex

If you experience any of the following symptoms of an allergy reaction, seek immediate medical attention: difficulty breathing or swelling in your lips, face, throat, or tongue.

Deconex can cause severe side effects. Deconex should be stopped immediately, and you need to call your doctor if:

  • Nervousness, dizziness, and sleep problems (insomnia).

There may be other side effects. Call your physician immediately if experiencing side effects; report side effects by contacting FDA at 1-800-FDA-1088.


Deconex should not be used if an MAO inhibitor has been taken in the last 14 days. There could be a dangerous drug interaction. The MAO inhibitors are isocarboxazid (linezolid), methylene blue injection, phenelzine, and tranylcypromine. Deconex will not be more effective if you take more than the recommended dosage. It may also cause side effects.

Before you take this drug

Deconex should not be used if MAO inhibitors have been taken in the last 14 days. It is possible that a dangerous drug interaction will occur. Included in MAO inhibitors are isocarboxazid (linezolid), phenelzine, and tranylcypromine. You must wait at least 14 days after you have stopped taking an MAO inhibitor before using this medication.

If you or a family member have:

  • High blood pressure
  • Heart Disease
  • Diabetes;
  • A thyroid condition;
  • There are several causes of urination issues.
  • Chronic coughs are caused by asthma, smoking, or another breathing disorder.

Before using any medicine, ask your doctor if you're pregnant or nursing. Children should only take this medicine after consulting their physician.

How to take Deconex?

Follow the instructions on the packaging or those prescribed by your physician. Cold and cough medicines are only to be used for a short time. Deconex should be given to children according to the instructions. Never use this medication to put a young child to sleep. Use the measuring tool provided to measure liquid medicines (not your kitchen spoon). Use the tablet along with water. If you change the brand, strength, or form of a medicine, your dose requirements may be different. Use the medication exactly as instructed on the package or prescribed by your physician to avoid any mistakes. If you take more of this medication than recommended, it will not be as effective and can cause side effects. If your symptoms don't improve after seven days or worsen, call your doctor. Also, you should contact your physician if there is a fever or rash or if headaches or migraines are present. Keep away from heat and moisture. Store at room temperature.

What happens if I miss the dose?

Deconex can be used as needed. You should not take any doses if you have a regular schedule. Never use more than one dose at a time.

What happens if I overdose?

Call 1-800-222-1222 immediately if you suspect poison, or seek immediate medical care.

What should be avoided?

Before taking any other cold or cough medicines, ask your doctor if they contain the same ingredients.

Interaction with other drug

Before taking any other medications that may cause sleepiness, such as opiates, muscle relaxants, sleeping pills, anxiety medicines, or seizure medicine, consult your doctor or pharmacist. Inform your doctor of all the medicines that you take. Included are prescription, over-the-counter, and herbal medicines. This list does not include all interactions.