What is Mydex (Guaifenesin Phenylephrine)?
There are many brands and forms of guaifenesin and phenylephrine available and not all brands are listed on this leaflet.
Guaifenesin is an expectorant. It helps loosen congestion in your chest and throat, making it easier to cough out through your mouth.
Phenylephrine is a decongestant that shrinks blood vessels in the nasal passages. Dilated blood vessels can cause nasal congestion (stuffy nose).
The combination of guaifenesin and phenylephrine is used to treat stuffy nose and sinus congestion, and to reduce chest congestion caused by the common cold or flu.
Guaifenesin and phenylephrine may also be used for other purposes not listed in this medication guide.
What is the most important information I should know about Mydex (Guaifenesin Phenylephrine)?
There are many brands and forms of guaifenesin and phenylephrine available and not all brands are listed on this leaflet.
Do not give this medication to a child younger than 4 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children.
Ask a doctor or pharmacist before using any other cough, cold, or allergy medicine. Guaifenesin and phenylephrine are contained in many combination medicines. Taking certain products together can cause you to get too much of a certain drug. Check the label to see if a medicine contains guaifenesin or phenylephrine.
What should I discuss with my healthcare provider before taking Mydex (Guaifenesin Phenylephrine)?
You should not use this medication if you are allergic to guaifenesin or phenylephrine, or to other decongestants, diet pills, stimulants, or ADHD medications.
Do not use guaifenesin and phenylephrine if you have used an MAO inhibitor such as furazolidone (Furoxone), isocarboxazid (Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam, Zelapar), or tranylcypromine (Parnate) in the last 14 days. Serious, life threatening side effects can occur if you use guaifenesin and phenylephrine before the MAO inhibitor has cleared from your body.
Ask a doctor or pharmacist if it is safe for you to take this medication if you have:
- heart disease or high blood pressure
- diabetes
- circulation problems
- glaucoma
- overactive thyroid; or
- enlarged prostate or problems with urination
It is not known if this medication may be harmful to an unborn baby. Do not use this medication without your doctor’s advice if you are pregnant.
This medication passes into breast milk and could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.
Artificially-sweetened liquid forms of cold medicine may contain phenylalanine. This would be important to know if you have phenylketonuria (PKU). Check the ingredients and warnings on
the medication label if you are concerned about phenylalanine.
Mydex Side Effects
What are the possible side effects of Mydex (Guaifenesin Phenylephrine)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop using this medication and call your doctor at once if you have any of these serious side effects:
- fast, pounding, or uneven heartbeat
- severe dizziness, anxiety, restless feeling, or nervousness
- easy bruising or bleeding, unusual weakness, fever, chills, body aches, flu symptoms
- dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven heartbeats, seizure); or
- nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes)
Less serious side effects may include:
- vomiting, upset stomach
- warmth, tingling, or redness under your skin
- feeling excited or restless (especially in children)
- sleep problems (insomnia)
- skin rash or itching
- headache; or
- dizziness
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Mydex Interactions
What other drugs affect Mydex (Guaifenesin Phenylephrine)?
Ask a doctor or pharmacist if it is safe for you to take guaifenesin and phenylephrine if you are also using any of the following drugs:
- medicines to treat high blood pressure
- a beta-blocker such as atenolol (Tenormin, Tenoretic), carvedilol (Coreg), labetalol (Normodyne, Trandate), metoprolol (Lopressor, Toprol), nadolol (Corgard), propranolol (Inderal, InnoPran), sotalol (Betapace), and others; or
- an antidepressant such as amitriptyline (Elavil, Vanatrip), doxepin (Sinequan), desipramine (Norpramin), imipramine (Janimine, Tofranil), nortriptyline (Pamelor), and others
This list is not complete and other drugs may interact with guaifenesin and phenylephrine. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor.
What should I avoid while taking Mydex (Guaifenesin Phenylephrine)?
This medication may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
Drinking alcohol can increase certain side effects of guaifenesin and phenylephrine.
Ask a doctor or pharmacist before using any other cough, cold, or allergy medicine. Guaifenesin and phenylephrine are contained in many combination medicines. Taking certain products together can cause you to get too much of a certain drug. Check the label to see if a medicine contains guaifenesin or phenylephrine.
Avoid taking this medication with diet pills, caffeine pills, or other stimulants (such as ADHD medications) without your doctor’s advice. Taking a stimulant together with a decongestant can increase your risk of unpleasant side effects.
Mydex Dosage
How should I take Mydex (Guaifenesin Phenylephrine)?
Use exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Cold medicine is usually taken only for a short time until your symptoms clear up.
Do not give this medication to a child younger than 4 years old. Always ask a doctor before giving cough or cold medicine to a child. Death can occur from the misuse of cough or cold medicine in very young children.
Measure the liquid form of this medicine with a special dose-measuring spoon or cup, not a regular table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.
Do not crush, chew, break, or open an extended-release tablet or capsule. Swallow it whole. Breaking or opening the pill may cause too much of the drug to be released at one time.
Take guaifenesin and phenylephrine with food if it upsets your stomach.
Talk with your doctor if your symptoms do not improve after 7 days of treatment, or if you have a fever with a headache, cough, or skin rash.
Drink extra fluids to help loosen the congestion and lubricate your throat while you are taking this medication.
Store at room temperature away from moisture and heat.
What happens if I overdose on Mydex (Guaifenesin Phenylephrine)?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include nausea, vomiting, numbness or tingly feeling, dizziness, and feeling restless or nervous.
What happens if I miss a dose of Mydex (Guaifenesin Phenylephrine)?
Since cough or cold medicine is taken as needed, you may not be on a dosing schedule. If you are taking the medication regularly, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
Edited from everydayhealth.com