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Home > Drug Category > Allergy Medication > Phenergan and Equivalent

Phenergan Information

Phenergan (promethazine) is a first-generation antihistamine with multiple therapeutic uses. It is primarily used to relieve symptoms of allergic conditions, such as seasonal and perennial allergic rhinitis, conjunctivitis, and allergic reactions to blood or plasma. However, due to its potent sedative properties, it is also widely used as a short-term sedative for insomnia, to prevent and control motion sickness, and as a pre-operative sedative for adults and children. Additionally, promethazine is a highly effective antiemetic, meaning it helps to prevent and control nausea and vomiting associated with various conditions, including surgery, motion sickness, and chemotherapy. The pharmacological action of promethazine is complex, as it acts on several different types of receptors in the body. It is a potent H1-receptor antagonist, which means it blocks the action of histamine, a natural substance in the body that triggers allergic reactions. Unlike newer, second-generation antihistamines, promethazine is lipophilic, allowing it to cross the blood-brain barrier easily. This property is what makes it so effective as a sedative and antiemetic, as it acts on the central nervous system. It also has anticholinergic effects, which can lead to a dry mouth and blurred vision. Furthermore, it exhibits a weak dopamine receptor-blocking effect, which contributes to its antiemetic action by targeting the chemoreceptor trigger zone in the brain.

Phenergen is available in various formulations, including tablets, oral solutions, and suppositories. The dosage and frequency of administration vary significantly depending on the condition being treated and the age of the patient. For allergies, a single dose is often sufficient, while for motion sickness, it should be taken before the travel begins. For use as a sedative or for nausea, it is usually administered as a short-term treatment. Due to its sedative effects, it is generally recommended to take it at bedtime.

Phenergen Side Effects

As a potent first-generation antihistamine, Phenergen is well-known for causing significant side effects, particularly central nervous system depression. The most common side effects are drowsiness, dizziness, and sedation. These effects can be pronounced and may persist into the next day. Other common side effects include a dry mouth, blurred vision, and difficulty urinating, which are related to its anticholinergic properties. Less common side effects can include restlessness, confusion, or a feeling of nervousness.

However, more serious side effects can occur, although they are rare. If you experience any of the following, you should stop taking the medication and seek immediate medical attention:

• Respiratory Depression: Promethazine can cause severe and potentially fatal respiratory depression. This risk is particularly high in children under two years of age, and it is a significant reason why the drug is contraindicated in this age group. Symptoms may include shallow or slow breathing.

• Neuroleptic Malignant Syndrome (NMS): Although rare, NMS is a potentially fatal reaction that can occur with drugs that have dopamine-blocking effects, including promethazine. Symptoms may include high fever, severe muscle stiffness, confusion, and changes in heart rate and blood pressure.

• Paradoxical Reactions: In some children and, less commonly, in adults, Phenergen may cause an unexpected reaction leading to hyperactivity, nightmares, agitation, and hallucinations.

• Seizures: Promethazine can lower the seizure threshold, and while rare, a seizure can be a profound side effect, particularly in individuals with a history of seizures or those on other medications that lower this threshold.

• Blood and Liver Effects: In rare cases, promethazine can cause serious blood disorders, such as agranulocytosis (a severe decrease in a type of white blood cell) and thrombocytopenia (low platelet count), which can lead to unusual bleeding or bruising. Rare instances of jaundice (yellowing of the skin or eyes) have also been reported, suggesting potential liver issues.

Phenergen Precautions

Before taking Phenergen, it is essential to have a thorough discussion with your healthcare provider about your medical history and any other medications you are taking. Phenergen has a black box warning from the FDA against use in children younger than two years of age due to the risk of fatal respiratory depression. It should also be used with extreme caution or avoided entirely in patients with severe lower respiratory tract conditions, such as asthma, COPD, or sleep apnea, as it can thicken respiratory secretions and worsen symptoms. It is contraindicated in patients who are in a comatose state, who have a history of paradoxical reactions to other antihistamines, or who have a history of bone marrow depression or angle-closure glaucoma. The sedative effects of promethazine can be significantly enhanced by other CNS depressants, including alcohol, opioids, barbiturates, and other sedatives, so concurrent use should be avoided. Due to the risk of Neuroleptic Malignant Syndrome, it should be used with caution in individuals with a history of this condition. Promethazine can interfere with some pregnancy tests and blood glucose tolerance tests, and it can cause photosensitivity. Use in the elderly should be carefully considered, as they are more susceptible to side effects like dizziness, sedation, and confusion. For pregnant or breastfeeding individuals, it is essential to consult a healthcare professional, as the drug can cross the placental barrier and be excreted in breast milk. It is crucial to avoid driving or operating heavy machinery until you know how the medication affects you.

Do I need a prescription to order Phenergan?

Yes, a prescription is required from your physician to order Phenergan.