From the Guidelines
Diphenhydramine (Benadryl) is given with metoclopramide (Reglan) to prevent dystonic reactions that can be caused by metoclopramide.
Rationale
- Metoclopramide is a medication used to treat nausea and vomiting, and it can cause dystonic reactions as a side effect 1.
- Diphenhydramine is an antihistamine that can be used to prevent or treat dystonic reactions caused by metoclopramide 1.
- The combination of metoclopramide and diphenhydramine is often used in clinical practice to minimize the risk of dystonic reactions and ensure effective management of nausea and vomiting.
Key Points
- Metoclopramide is recommended as a first-line treatment for chronic nausea, including opioid-related nausea 1.
- Diphenhydramine can be used to prevent or treat pruritus (itching) caused by opioids 1.
- The use of diphenhydramine with metoclopramide is a common practice in clinical settings, particularly in the management of nausea and vomiting caused by chemotherapy or opioids.
From the FDA Drug Label
If acute dystonic reactions should occur, inject 50 mg Benadryl (diphenhydramine hydrochloride) intramuscularly, and the symptoms usually will subside. If these symptoms should occur, inject 50 mg Benadryl (diphenhydramine hydrochloride) intramuscularly, and they usually will subside.
Diphenhydramine (Benadryl) is given with metoclopramide (Reglan) to prevent or treat extrapyramidal reactions (EPS), such as acute dystonic reactions, which can occur as a side effect of metoclopramide treatment 2, 2, 2.
From the Research
Rationale for Combination Therapy
The combination of diphenhydramine (Benadryl) and metoclopramide (Reglan) is used for several reasons:
- Diphenhydramine has antihistaminic and anticholinergic effects, which can help alleviate nausea and vomiting 3, 4
- Metoclopramide has antiemetic properties, but it can cause extrapyramidal side effects, which diphenhydramine may help mitigate 3
- The combination of diphenhydramine and metoclopramide may provide better efficacy in preventing postoperative nausea and vomiting compared to using either drug alone 4
Clinical Applications
The combination of diphenhydramine and metoclopramide is used in various clinical settings:
- Cancer chemotherapy: to prevent nausea and vomiting induced by cisplatin-based chemotherapy 3
- Postoperative care: to prevent nausea and vomiting after surgery 4
- Migraine treatment: as an adjuvant therapy to metoclopramide for acute migraine treatment, although its efficacy is debated 5, 6
- End-of-life care: as part of a combination antiemetic preparation (ABHR) to manage nausea and vomiting in cancer patients 7
Key Findings
- The combination of diphenhydramine and metoclopramide may be effective in reducing nausea and vomiting in certain clinical settings 4, 7
- Diphenhydramine may not provide absolute protection against the extrapyramidal side effects of metoclopramide 3
- The efficacy of diphenhydramine as an adjuvant therapy for acute migraine treatment is uncertain 5, 6