Phenylephrine is a medication that belongs to a class of drugs called sympathomimetics. It is a vasoconstrictor, which means that it works by narrowing the blood vessels in the nasal passages and sinuses, thereby reducing congestion and swelling. It is used to relieve nasal congestion caused by allergies, the common cold, and the flu. It is also used in combination with other medications to treat low blood pressure associated with anesthesia. It can be found as an ingredient in various over-the-counter and prescription products such as nasal sprays, tablets, and drops.

Common side effects of phenylephrine include:

• Headache

• Insomnia

• Nervousness or restlessness

• Rapid heartbeat

• High blood pressure

• Dizziness

• Nausea

• Stomach upset

• Constipation

Less common but serious side effects include:

• Allergic reactions such as hives, rash, or difficulty breathing

• Chest pain

• Tremors or shaking

• Seizures

• Unusual tiredness or weakness

• Unusual changes in mood or behavior

It is important to consult with a healthcare provider if you experience any of these serious side effects while taking phenylephrine. They will advise you on what to do next. This medication should be used with caution in people with high blood pressure, heart disease, diabetes, or thyroid disorder. And also it should be avoided if you are taking certain medications such as antidepressants, MAO inhibitors, and alpha blockers.