Patients may experience a variety of promethazine side effects when taking the drug for reasons such as allergic reactions, sedation, or treatment of motion sickness. Two of the most common issues that patients experience are feelings of drowsiness and lightheadedness. Many people have gastrointestinal issues including nausea and dry mouth. Cardiovascular problems like changes in blood pressure or heart rate may occur, as can skin issues like rash, jaundice, and increased sensitivity to sunlight. Other fairly frequent side effects can include difficulty breathing, mood changes, and muscle spasms.
Promethazine side effects that involve the central nervous system are typically the issues that patients most frequently report. Many people become dizzy or lightheaded when taking this drug, or feel confused and disoriented. Some may feel tired and drowsy, though others experience difficulty sleeping and insomnia; patients have also complained of a tendency to have nightmares. Feelings of restlessness and excitability are common. Patients may notice that their vision becomes blurred, and some have also reported having hallucinations.
Problems that affect the digestive system are also common promethazine side effects. One common complaint is dry mouth. Feelings of nausea and vomiting are frequently an issue, and some patients also experience loss of appetite from the medication.
The cardiovascular system can also be negatively affected by promethazine. Patients may develop hypertension, or high blood pressure, or they can develop hypotension, which is low blood pressure. Some may experience an increase in heart rate, known as tachycardia; others might have bradycardia, where the heart rate slows down. Heart arrhythmias can also occur.
Another common location for promethazine side effects to show up is the skin. People taking the drug may develop an itchy rash or hives. They may notice yellowing of their skin, also known as jaundice. Another common issue is an increased sensitivity to sunlight, or photosensitivity, which can make people prone to sunburn.
There is a wide variety of other promethazine side effects that patients may also experience. Sometimes people have trouble breathing; it may slow down or become irregular, which can potentially become dangerous. Mental state and mood can also be changed by the drug; anxiety, euphoria, and hysteria have all been reported while taking promethazine. Patients might have a tendency to bruise or bleed easily. They may notice that their muscles move uncontrollably, jerking or spasming, and some can even have seizures as well.