Diphenhydramine for nausea
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Diphenhydramine for Nausea: Clinical Contexts and Effectiveness
Diphenhydramine for Chemotherapy-Induced Nausea and Vomiting
Diphenhydramine has been studied as an adjuvant antiemetic in patients receiving chemotherapy, particularly with cisplatin. When combined with metoclopramide, diphenhydramine did not significantly improve nausea and vomiting control compared to metoclopramide alone, though it did cause more sedation and limited activity. The side effects were generally minimal and well tolerated, but overall, diphenhydramine was not found to be a useful addition for this purpose . In another study, a combination of metoclopramide, diphenhydramine, droperidol, and dexamethasone provided high rates of protection from nausea and vomiting in patients receiving cisplatin, with mild and infrequent toxicities. This suggests that diphenhydramine may have a role as part of a multi-drug regimen, though its individual contribution is less clear . In pediatric patients, the combination of metoclopramide and diphenhydramine was less effective than ondansetron for controlling chemotherapy-induced nausea and vomiting, especially with cisplatin regimens, and was associated with more side effects .
Diphenhydramine for Postoperative Nausea and Vomiting (PONV)
Diphenhydramine has shown some benefit in reducing postoperative nausea and vomiting when used in combination with other antiemetics. In patients undergoing abdominal hysterectomy, the combination of metoclopramide and diphenhydramine, along with dexamethasone, resulted in significantly lower rates of nausea and vomiting compared to either drug alone or placebo when added to patient-controlled morphine analgesia . Another study found that an initial bolus of diphenhydramine followed by a higher ratio of diphenhydramine-morphine mixture in patient-controlled analgesia significantly reduced the incidence and severity of postoperative nausea and vomiting, without increasing side effects . Additionally, in bariatric surgery patients, adding diphenhydramine to acetaminophen and ondansetron reduced the incidence and severity of PONV and pain compared to acetaminophen and ondansetron alone .
Diphenhydramine in Hyperemesis Gravidarum
For hyperemesis gravidarum (severe nausea and vomiting in pregnancy), a protocol combining metoclopramide and diphenhydramine improved vomiting symptoms and had fewer adverse events compared to a droperidol-diphenhydramine regimen. Both protocols were similar in reducing nausea, length of hospital stay, and rehospitalization rates, suggesting that the metoclopramide-diphenhydramine combination is a reasonable option for managing this condition .
Diphenhydramine for Nausea in Other Settings
Diphenhydramine, when combined with droperidol, was effective in rapidly reducing nausea, vomiting, and abdominal pain in patients with cannabinoid hyperemesis syndrome, with significant symptom improvement within 30 to 120 minutes after treatment . In a study involving exposure to high magnetic fields (7T MRI), diphenhydramine reduced the strength of vertigo, which is often accompanied by nausea, suggesting a potential preventive role in this specific context .
Comparative Effectiveness and Side Effects
While diphenhydramine can contribute to antiemetic regimens, especially in combination with other drugs, it is generally less effective than newer agents like ondansetron for chemotherapy-induced nausea and vomiting, particularly with highly emetogenic regimens . Sedation is a common side effect, but it is usually mild and well tolerated 157. In some regimens, diphenhydramine is included to prevent extrapyramidal side effects from other antiemetics, though it does not provide complete protection 13.
Conclusion
Diphenhydramine alone is not highly effective for nausea, but it can be beneficial as part of combination therapy for postoperative nausea and vomiting, hyperemesis gravidarum, and certain acute syndromes like cannabinoid hyperemesis. Its role is less clear and less effective in chemotherapy-induced nausea compared to modern antiemetics. Sedation is the most notable side effect, but it is generally well tolerated. Overall, diphenhydramine may be considered as an adjunct in specific clinical scenarios, particularly when other antiemetics are also used.
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