Sixteen RCTs were included (n=2,998 analysed): 11 parallel-group studies; three double-dummy studies; and two crossover studies. Seven studies scored 5 out of 5 points on the Jadad scale and nine scored 4 points. Drop-out rates ranged from 0 to 23%.
Compared to placebo, MFNS was associated with a statistically significant reduction in the following outcomes: total nasal symptom scores (SMD -0.56, 95% CI -0.71 to -0.41, p<0.00001; 10 RCTs, n=1,878); nasal stuffiness (SMD -0.41, 95% CI -0.56 to -0.27, p<0.00001), rhinorrhoea (SMD -0.44, 95% CI -0.66 to -0.21, p=0.0001), sneezing (SMD -0.40, 95% CI -0.57 to -0.23, p<0.00001) and nasal itching (SMD -0.39, 95% CI -0.53 to -0.25, p<0.00001) all based on seven studies (n=1,582); and non-nasal symptoms scores (SMD -0.30, 95% CI -0.43 to -0.18, p<0.00001; four RCTs, n=1,009). Heterogeneity was significant for total nasal symptoms scores (I2=58%), nasal stuffiness (I2=51%), rhinorrhoea (I2=79%) and sneezing (I2=64%).
MFNS was associated with a significant increase in nasal airflow (SMD 0.32, 95% CI 0.08 to 0.56, p=0.01; three RCTs, I2=33%), but studies used different methods to measure air flow.
There was no statistically significant difference in adverse events between MFNS and placebo (nine RCTs).
The funnel plot showed no evidence of publication bias.