Phenylephrine / promethazine Side Effects

Medically reviewed by Drugs.com. Last updated on Oct 1, 2023.

Applies to phenylephrine / promethazine: oral solution, oral syrup.

Serious side effects

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of high or low blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
• Fast or slow heartbeat.
• Trouble passing urine.
• Feeling very tired or weak.
• Hallucinations (seeing or hearing things that are not there).
• Mood changes.
• Ringing in ears.
• Seizures.
• Any unexplained bruising or bleeding.
• Trouble controlling body movements, twitching, change in balance, trouble swallowing or speaking.
• Change in eyesight.
• Yellow skin or eyes.
• A very bad and sometimes deadly health problem called neuroleptic malignant syndrome (NMS) may happen. Call your doctor right away if you have any fever, muscle cramps or stiffness, dizziness, very bad headache, confusion, change in thinking, fast heartbeat, heartbeat that does not feel normal, or are sweating a lot.
• This drug may cause very bad and sometimes deadly breathing problems. Call your doctor right away if you have slow, shallow, or trouble breathing.
• Low white blood cell counts have rarely happened with this drug. This may lead to a higher chance of getting an infection. Tell your doctor if you have ever had a low white blood cell count. Call your doctor right away if you have signs of infection like fever, chills, or sore throat.

Other side effects

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Feeling sleepy.
• Dizziness.
• Feeling tired or weak.
• Feeling nervous and excitable.
• Dry mouth.
• Upset stomach or throwing up.
• Not able to sleep.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

For Healthcare Professionals

Applies to phenylephrine/promethazine: oral syrup.

General

One of the most commonly reported adverse reactions has included drowsiness.^[Ref]

Nervous system

Promethazine:

Frequency not reported: Sedation, sleepiness, somnolence, dizziness, tremor, weakness, and extrapyramidal symptoms such as oculogyric crisis, torticollis, and tongue protrusion, incoordination, seizures, neuroleptic malignant syndrome

Phenylephrine:

Frequency not reported: Dizziness, tremor, weakness^[Ref]

Psychiatric

Promethazine:

Frequency not reported: Euphoria, confusion, disorientation, restlessness, anxiety, nervousness, excitation, catatonic-like states, hysteria, hallucinations, nightmares, insomnia, delirium, agitated behavior

Phenylephrine:

Frequency not reported: Restlessness, anxiety, nervousness

Cardiovascular

Promethazine:

Frequency not reported: Increased or decreased blood pressure, tachycardia, bradycardia, faintness

Phenylephrine:

Frequency not reported: Hypertension^[Ref]

Ocular

Promethazine:

Frequency not reported: Blurred vision, diplopia^[Ref]

Gastrointestinal

Promethazine:

Frequency not reported: Dry mouth, nausea, vomiting^[Ref]

Hematologic

Promethazine:

Frequency not reported: Leukopenia, thrombocytopenia, thrombocytopenic purpura, agranulocytosis^[Ref]

Dermatologic

Promethazine:

Frequency not reported: Dermatitis, photosensitivity, urticaria, angioneurotic edema^[Ref]

Respiratory

Promethazine:

Frequency not reported: Respiratory distress, asthma, nasal stuffiness, apnea

Phenylephrine:

Frequency not reported: Respiratory distress^[Ref]

Hepatic

Promethazine:

Frequency not reported: Jaundice

Other

Promethazine:

Frequency not reported: Lassitude, tinnitus, fatigue

Phenylephrine:

Frequency not reported: Precordial pain

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer