Gronborg 1983.

Methods	Randomised, double‐blind, placebo‐controlled, cross‐over design
Participants	N recruited: 34 N analysed: 30 ("Four subjects were excluded as it became evident on the second day that their cold symptoms had disappeared") Country: Denmark Age: range was 18 to 32 years, mean age was 23.0 years Inclusion criteria: a nose blowing of at least 0.1 mL could be provided in the observation period Exclusion criteria: none stated. "Four subjects were excluded as it became evident on the second day that their cold symptoms had disappeared" Diagnostic criteria: sudden occurrence of sneezing, nasal discharge and blockage, or at least of 2 of these symptoms. Nasal symptoms lasting 12 to 48 hours. The student felt sure that he/she caught a cold. The investigator observed signs of a cold (nasal voice, sneezing, nose blowing) during the 10 to 15 min observation period
Interventions	Nasal decongestant dose: single dose of 100 mg norephedrine in a sustained release form Administration: single dose Oral tablets (cross‐over design: each participant received treatment on 1 day and placebo on another day) Follow‐up: 1 day Measurements: nasal airway resistance measured by posterior rhinomanometry and nasal peak flow measured immediately after rhinomanometry, using a Write Peak Flow minimeter. This was measured before and 2 hours after treatment Self‐assessment test for nasal blockage (scale from 0 "completely free" to 5 "complete blockage") and recording of numbers of sneezes and nose blowing per hour. This was measured hourly (2 to 10 hours after treatment) Side effects: a questionnaire about new symptoms
Outcomes	Study does not explicitly state which of the measured outcomes were primary or secondary We assumed the following: Primary outcomes: nasal airway resistance, nasal peak flow, self‐assessment of nasal blockage Secondary outcomes: numbers of sneezes and nose blowing per hours, side effects
Notes	Funding: H. Lundbeck and Co. funded the study and provided the medication Declarations of interest: not provided
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation not described, only that "each student got a single dose of 100 mg norephedrine in sustained release form and placebo in randomised order"
Allocation concealment (selection bias)	Unclear risk	No mention of allocation concealment described but due to cross‐over design, all patients enrolled in the study received both treatment and placebo
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Study reports that it is double‐blind: "the tablets were supplied in coded vials by H. Lundbeck and Co., Copenhagen, Denmark"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Study reports that it is double‐blind. For rhinomanometry, because "the reading of the V2 value depends to some degree upon the investigator’s interpretation of the curve", "in order to eliminate this as a potential source of bias, [the authors] have added a computer to the set‐up, which digitally displays the means V2 value of five consecutive respiration curves."
Incomplete outcome data (attrition bias) All outcomes	Low risk	4 of the original 34 students who fulfilled the inclusion criteria "were excluded as it became evident on the second day that their cold symptoms had disappeared". The remaining 30 students completed the trial
Selective reporting (reporting bias)	Low risk	All intended outcomes were reported
Other bias	Unclear risk	H. Lundbeck and Co. funded the study and provided the medication