A Cochrane review included 10 studies with a total of 792 subjects. In six trials, Ginkgo biloba extract was given as oral tablets 120 mg to 240 mg per day for 20 to 28 days. In four trials, intravenous injections were used, the dosage being from 15 ml to 20 ml (Ginkgo biloba extract 17.5 mg per 5 ml) per day for 14 to 30 days. The only placebo-controlled trial assessed to be of good quality failed to show an improvement of neurological deficit at the end of treatment (weighted mean difference (fixed) 0.81; 95% CI –8.9 to 10.52). In nine trials, all assessed to be of inferior quality, Ginkgo biloba extract was associated with a significant increase in the number of improved patients (Peto odds ratio (OR) 2.66; 95% confidence interval (CI) 1.79 to 3.94).
Comment: The quality of evidence is downgraded by serious limitations in study quality, imprecise data and high probability of reporting bias.