Diphenhydramine efficacy for nausea
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Diphenhydramine Efficacy for Nausea: Clinical Evidence Overview
Diphenhydramine for Postoperative Nausea and Vomiting (PONV)
Several studies have evaluated diphenhydramine’s effectiveness in reducing postoperative nausea and vomiting. When added to patient-controlled morphine analgesia, diphenhydramine alone did not significantly reduce nausea compared to morphine alone. However, a higher ratio of diphenhydramine to morphine (4.8:1) combined with an initial bolus at anesthesia induction did significantly lower the incidence and severity of postoperative nausea and vomiting, as well as the need for rescue antiemetics, without increasing side effects like sedation or dry mouth . Additionally, combining diphenhydramine with metoclopramide and dexamethasone further reduced postoperative nausea and vomiting compared to either drug alone in patients receiving morphine analgesia after surgery . In bariatric surgery, adding diphenhydramine to acetaminophen and ondansetron also significantly reduced PONV rates and pain in the first 24 hours after surgery .
Diphenhydramine in Chemotherapy-Induced Nausea
For patients undergoing cisplatin-based chemotherapy, diphenhydramine has been used as part of combination antiemetic regimens. When combined with metoclopramide, droperidol, and dexamethasone, diphenhydramine contributed to high rates of complete protection from nausea and vomiting, with mild and infrequent side effects . However, another study found that adding diphenhydramine to metoclopramide did not significantly improve antiemetic efficacy compared to metoclopramide alone, though it did increase sedation . In pediatric patients, the combination of metoclopramide and diphenhydramine was less effective than ondansetron for controlling chemotherapy-induced nausea, especially in regimens containing cisplatin .
Diphenhydramine for Nausea in Pregnancy
In the management of hyperemesis gravidarum (severe nausea and vomiting during pregnancy), a protocol combining metoclopramide and diphenhydramine improved vomiting symptoms and had fewer adverse events compared to a droperidol-diphenhydramine regimen. However, both protocols were similarly effective in reducing nausea and the need for rehospitalization .
Other Uses: Vertigo-Induced Nausea
Diphenhydramine has also been shown to reduce the strength of vertigo and associated nausea induced by exposure to ultra-high static magnetic fields, suggesting a potential preventive role in this specific context .
Conclusion
Diphenhydramine can be effective in reducing nausea and vomiting, particularly when used in combination with other antiemetics such as metoclopramide, dexamethasone, or ondansetron, and at higher dosing ratios in postoperative settings 134. Its efficacy as a single agent or as an adjunct in chemotherapy-induced nausea is less clear, with some studies showing limited additional benefit and increased sedation 2710. In pregnancy-related nausea, it appears to be a safe and effective option when combined with metoclopramide . Overall, diphenhydramine’s antiemetic efficacy is context-dependent and often enhanced when used as part of a multimodal regimen.
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