Promethazine Risks, Warnings, and Complications

SEVERE BREATHING PROBLEMS: Promethazine can cause life-threatening respiratory depression in children younger than 2 years of age, especially if they have health conditions such as sleep apnea or chronic obstructive pulmonary disease or if they are taking other medications that also affect breathing. Adults who have breathing problems, are taking other medications such as certain pain relievers (opioids) or sleeping pills, or are drinking alcohol are also at increased risk.

SEVERE TISSUE INJURY: Intravenous promethazine can cause skin irritation and cause the death of skin tissue. This can result in an infection, requiring surgery, or even limb amputation. The risk is higher if promethazine is given through the IV route. This is why instead of intravenous promethazine, the medicine is given intramuscularly (by injection into a muscle). Be vigilant for skin changes if you have received a promethazine injection. Seek immediate medical care if you notice skin darkening, pain, burning, or swelling.

EFFECT ON FOCUS AND CONCENTRATION: Taking promethazine can cause severe drowsiness, which can affect your concentration and focus. You should avoid driving a motor vehicle, operating machinery, or doing anything that requires you to be alert until you know how promethazine affects you.

SEIZURES: In people who have a history of epilepsy or seizures, taking promethazine can cause more frequent seizures. Give your healthcare professional a complete medical history and tell them if you have seizures or are taking medications to control seizures.

UNCONTROLLED BODY MOVEMENTS: In a small number of people, promethazine can cause uncontrolled body movements, such as an abnormal position of the neck, abnormal eye movements, tongue thrusting, and jerky movements of the limbs, or tremors. These are called extrapyramidal symptoms (EPS). The risk of extrapyramidal symptoms with promethazine is higher in older adults (those over age 65) and for those on long-term promethazine treatment. Tell your healthcare provider right away if you notice any unusual body movements while on promethazine.

NEUROLEPTIC MALIGNANT SYNDROME: Very rarely, promethazine can cause a condition called neuroleptic malignant syndrome (NMS). This is a potentially life-threatening condition that requires immediate treatment. The risk of neuroleptic malignant syndrome is higher in people who take antipsychotic medications. Give your healthcare provider and pharmacist a complete list of your medications before starting promethazine to avoid any possible drug interactions. Symptoms of NMS may include fever, confusion, muscle stiffness, sweating, and changes in blood pressure and heart rate. Seek immediate medical help if you notice these symptoms.

FALL IN WHITE BLOOD CELL LEVELS: Promethazine can lead to a fall in the number of white blood cells in the body. These cells help the body fight infections. Having too few white blood cells can make it harder to fight off infections. This side effect of promethazine is serious and potentially life-threatening. The risk of this occurring is higher in people receiving certain chemotherapy drugs that cause bone marrow depression. If you are taking promethazine regularly, your healthcare provider may ask you to have blood tests done to keep an eye on your white blood cell count.