Sodium bicarbonate–diphenhydramine combo beneficial in acute peripheral vertigo

Combination treatment with sodium bicarbonate plus diphenhydramine appears to provide better symptom relief for patients with acute peripheral vertigo compared with diphenhydramine alone, as shown in a study.

At 60 min after treatment, vertigo severity as assessed using a 10-point visual analogue scale (VAS) decreased significantly for patients who received the combination of sodium bicarbonate plus diphenhydramine than those who received diphenhydramine alone (mean change in VAS score, –5.6 vs –4.4; p=0.01). The treatment effect was most pronounced among men (mean change in VAS score, –5.3 vs –3.4; p=0.003), younger patients (mean change in VAS score, –5.8 vs –3.8; p=0.006), and those without a history of vertigo (mean change in VAS score, –6.2 vs –4.4; p=0.008). [JAMA Netw Open 2025;8:e2541472]

Meanwhile, the improvement in vertigo severity did not differ between patients who received sodium bicarbonate only and those who received diphenhydramine alone (mean change in VAS score, –5.1 vs –4.4; p=0.34). The treatment effect with sodium bicarbonate vs diphenhydramine was better among men (mean change in VAS score, –5.5 vs –3.4; p=0.001) and those without previous vertigo episodes (mean change in VAS score, –5.9 vs –4.4; p=0.03).

Rescue therapy was used less frequently in the combination group than in the diphenhydramine group (17.8 percent vs 46.7 percent; p<0.001). No differences were observed in nausea scores or emergency department (ED) length of stay across the three treatment groups.

In terms of safety, lethargy was more common with diphenhydramine vs sodium bicarbonate (30.1 percent in the combination group and 38.7 percent in the diphenhydramine alone group vs 8.1 percent; p<0.001). On the other hand, injection discomfort occurred with greater frequency with sodium bicarbonate vs diphenhydramine (28.8 percent in the combination group and 17.6 percent in the sodium bicarbonate alone group vs 8 percent; p=0.004).

While the findings favour the combination of diphenhydramine plus sodium bicarbonate for acute vertigo treatment, the investigators emphasized that sodium bicarbonate may be a safer option than diphenhydramine owing to the lower risk of lethargy. “This is particularly important for patients who need to drive or work, as well as for ED patients who are at a higher risk of falls.”

Meanwhile, “patients treated with sodium bicarbonate should be informed of possible tenderness during and after injection or of the subsequent risk of vasculitis; slow infusion administration may slightly reduce this risk,” they added.

For younger male patients without a history of vertigo, who may have a reduced response to diphenhydramine treatment, sodium bicarbonate or combination therapy can be considered, according to the investigators.

The study included 222 patients (mean age 57.9 years, 67.6 percent female) with peripheral vertigo within 24 h of onset. More than half of the patients (59.9 percent) had experienced vertigo, and the mean time from symptom onset to the ED visit was 6.5.

The patients were randomly assigned to receive 30 mg of intravenous diphenhydramine, 66.4 mEq of sodium bicarbonate, or both agents. The primary outcome was change in vertigo severity at 60 min after treatment. Key secondary outcomes included change in nausea severity using a 10-point VAS, rescue medication use, ED length of stay, and adverse effects.