Promethazine is a medication used to relieve and prevent nausea, vomiting, and motion sickness. It also has sedative properties. The medication works by affecting chemical messengers in the brain, calming the body’s response to stimuli that cause sickness. It is available in various forms for flexible administration.
How Promethazine Addresses Nausea
Promethazine alleviates nausea and vomiting by acting on the brain’s vomiting center. As a first-generation antihistamine, its primary mechanism involves blocking histamine H1 receptors in the brain. This suppresses signals that trigger nausea and vomiting.
The medication also has anticholinergic properties, blocking acetylcholine, a neurotransmitter. This effect contributes to its antiemetic action by inhibiting the vagus nerve’s influence on the gastrointestinal tract. Promethazine also calms the central nervous system through its sedative effects. Additionally, it antagonizes dopamine receptors in the medullary vomiting center, enhancing its antiemetic properties.
Forms and Administration
Promethazine is available as oral tablets, liquid solutions, syrups, and rectal suppositories. In clinical settings, it can also be administered as an injection. The choice of form depends on the patient’s age, ability to swallow, and nausea severity.
Oral forms can be taken with or without food; taking it with food may reduce stomach upset. For adults, a common dosage for nausea and vomiting is 12.5 mg to 25 mg, taken every 4 to 6 hours as needed. A healthcare professional determines specific dosages based on individual condition and age.
Potential Adverse Effects
Promethazine can cause side effects. Common effects include drowsiness and dry mouth, stemming from its sedative and anticholinergic actions. Blurred vision and dizziness are also possible.
Some individuals may experience confusion, nervousness, or difficulty sleeping. These effects are usually temporary and may lessen as the body adjusts to the medication.
Specific Warnings and Precautions
Promethazine has specific warnings and precautions. It is contraindicated in children younger than two years due to the risk of fatal respiratory depression. Caution is also advised for children aged two years and older, as respiratory depression remains a concern.
Individuals with pre-existing medical conditions should use promethazine with caution or avoid it. This includes those with asthma, lung problems, glaucoma, an enlarged prostate, or stomach and bowel issues. Always consult a healthcare provider before use if you have these conditions.
Promethazine can intensify the effects of other central nervous system depressants like alcohol, sedatives, narcotic pain relievers, and tranquilizers, leading to increased drowsiness and impaired mental or physical abilities. Avoid alcohol consumption. Due to sedative effects, avoid activities requiring mental alertness, such as driving or operating machinery, until you know how the medication affects you. Promethazine can also increase sun sensitivity, so use protective measures like sunscreen and clothing outdoors.