The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring.
To help your doctor and pharmacist give you the best care, be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor's approval.
Some products that may interact with this drug include: other decongestants (taken by mouth or sprayed into the nose), tricyclic antidepressants (such as nortriptyline, amitriptyline).
Taking MAO inhibitors with this medication may cause a serious (possibly fatal) drug interaction. Avoid taking MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine) during treatment with this medication. Most MAO inhibitors should also not be taken for two weeks before treatment with this medication. Ask your doctor when to start or stop taking this medication.
Phenylephrine may decrease the effectiveness of some blood pressure medications (such as beta blockers, guanethidine, methyldopa, mecamylamine).
Guaifenesin and phenylephrine are available in both prescription and nonprescription products. Check the labels of all your medications to make sure you are not taking more than one product containing guaifenesin or phenylephrine.
Guaifenesin can affect the results of certain lab tests (such as urine levels of certain acids). Make sure laboratory personnel and all your doctors know you use this drug.
This document does not contain all possible interactions. Before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.