A Cochrane review 1 included three trials with 189 participants. One study showed a significant difference in hearing recovery in the vasodilator group (carbogen combined with a course of several other drugs) compared to the control group (a course of several other drugs alone) (76.9% in treatment group and 50% in control group, P < 0.05). Another study only showed a significant improvement (44% versus 13%) in higher frequencies in the vasodilator group (prostaglandin E1 + steroid) compared with the control group (placebo and steroid), no difference having been shown in overall hearing gain. In the third study the vasodilator group (naftidrofuryl and low-molecular weight dextran) showed an 70% improvement only in lower frequencies over the control group (placebo and low-molecular weight dextran, 40%).
Comment: The quality of evidence is downgraded by study quality (inadequate or unclear allocation concealment and blinding) and by imprecise results (few patients and wide confidence intervals, differences in interventions).
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