Promethazine is an antihistamine with sedative, antiemetic, and anticholinergic properties. It is commonly used to treat nausea, vomiting, allergies, motion sickness, and insomnia [1].
How does promethazine work for nausea and vomiting?
Promethazine functions by blocking histamine H1 receptors in the brain's chemoreceptor trigger zone (CTZ). The CTZ is involved in the vomiting reflex. By inhibiting histamine's action in this area, promethazine can help reduce feelings of nausea and prevent vomiting [1].
What are the different forms of promethazine available?
Promethazine is available in several forms, including oral tablets, capsules, syrup, and suppositories. It is also available as an injectable solution for intramuscular or intravenous administration. These different formulations allow for various routes of administration depending on the patient's needs and the severity of their symptoms [2].
When was promethazine first approved?
Promethazine was first approved by the U.S. Food and Drug Administration (FDA) in 1951 [3].
What are the potential side effects of promethazine?
Common side effects of promethazine include drowsiness, dizziness, blurred vision, dry mouth, and constipation. More serious side effects can include confusion, restlessness, tremors, and a severe drop in blood pressure, particularly with intravenous administration [1]. Due to its sedative effects, patients are advised not to drive or operate heavy machinery after taking promethazine [4].
Are there any warnings or precautions for using promethazine?
Promethazine should be used with caution in individuals with respiratory conditions, such as asthma or emphysema, as it can suppress the cough reflex. It is also contraindicated in children under two years of age due to the risk of fatal respiratory depression [4]. Patients with certain medical conditions, including glaucoma, prostate enlargement, or liver disease, should consult their doctor before using promethazine [1].
Can promethazine be used during pregnancy?
The use of promethazine during pregnancy should be discussed with a healthcare provider. While generally considered to have a low risk, particularly in the second and third trimesters, it has been associated with potential risks in the first trimester and may cause side effects in newborns if used near term [1].
How does promethazine compare to other antiemetics?
Compared to other antiemetics like ondansetron, promethazine has a broader range of uses beyond nausea and vomiting, including its antihistamine and sedative properties. However, ondansetron may be preferred for chemotherapy-induced nausea and vomiting due to its specific action on serotonin receptors and potentially fewer sedating side effects [5]. Promethazine's sedative effect can be a benefit for patients experiencing insomnia alongside nausea, but a drawback for those needing to remain alert [1].
What are the patent and exclusivity details for promethazine?
As promethazine was first approved in 1951, its original patents have long expired. It is considered a generic medication, meaning that its manufacturing and sale are not restricted by active drug patents or market exclusivity [3]. DrugPatentWatch.com tracks patent information for pharmaceuticals, and while promethazine itself is off-patent, any new formulations or delivery methods could be subject to new patent applications [6].
What is the typical cost of promethazine?
Promethazine is widely available as a generic medication, which generally makes it a cost-effective treatment option. The price can vary depending on the dosage form, strength, and pharmacy, but it is typically inexpensive compared to newer, branded medications [7].
Sources:
1. DrugBank Online
2. National Library of Medicine - MedlinePlus
3. FDA Orange Book
4. Mayo Clinic
5. National Cancer Institute
6. DrugPatentWatch.com
7. GoodRx