Precautions
Before taking this medication, tell your doctor or pharmacist:
- If you are allergic to phenylephrine or guaifenesin; or if you have any other allergies. Also tell your doctor if you have had bad reactions to similar drugs (sympathomimetics such as ephedrine).
- If you are to undergo any surgery.
- Pregnant or breastfeeding.
- Your medical history, especially of:
- Breathing Problems (such as Emphysema, Chronic Bronchitis, Asthma, Smoker’s Cough)
- Cough With Blood or Large Amounts of Mucus
- High Blood Pressure
- Heart Disease (such as Chest Pain, Heart Failure, Heart Attack)
- Fast, Slow or Irregular Heartbeat
- Diabetes
- Glaucoma
- Difficulty Urinating (such as Due to Enlarged Prostate)
- Overactive Thyroid (Hyperthyroidism)
This drug may cause dizziness, drowsiness or blurred vision. Avoid activities requiring alertness or clear vision such as driving until you are sure you can perform such activities safely. Limit the use of alcohol and certain other medications that cause drowsiness.
Older adults and children may be more sensitive to the side effects of this drug, especially dizziness, drowsiness, mental or mood changes, constipation, fast heartbeat, trouble urinating, or blood pressure changes.
Interactions
Drug interactions may either lessen the effectiveness of this drug or heighten the risk for severe side effects. It’s important to inform your doctor all the medication including prescription and non-prescription and herbal medicines you are taking or going to take.
Possible interactions with this drug are:
- Other Decongestants
- Tricyclic Antidepressants (such as Nortriptyline, Amitriptyline)
- Mao Inhibitors (Isocarboxazid, Linezolid, Methylene Blue, Moclobemide, Phenelzine, Procarbazine, Rasagiline, Selegiline, Tranylcypromine)
- Beta Blockers, Reserpine, Guanethidine, Methyldopa, Mecamylamine
- Other Products that also Contain Guaifenesin and Phenylepherine
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 to avoid false results.