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). This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist 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/irregular heartbeat, diabetes, a certain eye problem (glaucoma), difficulty urinating (such as due to enlarged prostate), overactive thyroid (hyperthyroidism).

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Liquid forms of this product may contain sugar, aspartame, and/or alcohol. Caution is advised if you have diabetes, liver disease, phenylketonuria (PKU), or any other condition that requires you to limit/avoid these substances in your diet. Ask your doctor or pharmacist about using this product safely.

Children may be more sensitive to the side effects of this drug, especially nervousness, irritability, and high blood pressure.

Older adults may be more sensitive to the side effects of this drug, especially fast/irregular heartbeat, dizziness, problems urinating, trouble sleeping, or confusion.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

Phenylephrine may pass into breast milk and could have undesirable effects on a nursing infant. It is unknown if guaifenesin passes into breast milk. Consult your doctor before breastfeeding.