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• Interactions

Many drugs can interact with guaifenesin and theophylline. Below is just a partial list. Tell your doctor if you are using:

• birth control pills;

• an antibiotic such as ciprofloxacin (Cipro), clarithromycin (Biaxin), erythromycin (Ery-Tab, E.E.S, E-Mycin, others), ketoconazole (Nizoral), levofloxacin (Levaquin), rifampin (Rifadin, Rifamate, Rimactane);

• a thyroid hormone such as levothyroxine (Synthroid, Levoxyl, Levothroid, others);

• an interferon product such as Intron A, Alferon N, Infergen, Roferon-A, Betaseron, Avonex, Actimmune, and others;

• a calcium channel blocker such as diltiazem (Cardizem, Dilacor XR, Tiazac), nifedipine (Procardia, Adalat), verapamil (Verelan, Calan, Isoptin), and others;

• a beta-blocker such as atenolol (Tenormin), metoprolol (Lopressor, Toprol), propranolol (Inderal), timolol (Blocadren), and others;

• asthma medication such as albuterol (Ventolin, Proventil, Volmax, others), salmeterol (Serevent), and others;

• a diuretic (water pill); or

• seizure medication such as phenytoin (Dilantin) or phenobarbital (Luminal, Solfoton).

There are many other medicines that can interact with guaifenesin and theophylline. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a list with you of all the medicines you use and show this list to any doctor or other healthcare provider who treats you.

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.

Call your doctor at once if you have a serious side effect such as:

• seizure (convulsions);

• fast or uneven heart rate; or

• severe nausea or vomiting.

Less serious side effects may include:

• mild skin rash;

• slight nausea, decreased appetite, or weight loss;

• restlessness, tremor, or insomnia; or

• headache, lightheadedness, or dizziness.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.