Bokaie 2013.

Methods	RCT
Participants	Included: 18 to 25 years of age, living in a dormitory, non‐smoker, no systemic disease, not taking an oral contraceptive pill (OCP) and other hormonal and herbal drugs prior to and during the menstrual cycle, regular menstruation, and suffering from moderate to severe primary dysmenorrhoea Excluded: intolerance to fennel drop, no desire to take any of the treatments, and taking other NSAIDs during the study Age: mean age of fennel drop group = 21.07 years; control = 21.17 years Source: Roghaye female student dormitory of Shahid Sadoughi University of Medical Sciences Location: Iran
Interventions	Group 1: 25 drops of fennelin (Foeniculum vulgare) 2% every 6 hours (each 1 mL drop contained 15.5 mg antole), mefenamic acid capsule 250 mg every 6 hours, if necessary (N = 30, 29 analysed) Group 2: mefenamic acid capsule 250 mg every 6 hours, if necessary (N =30) Students were followed up for two menstruation cycles
Outcomes	Primary Pain severity (VAS scale 10 cm) before menstruation and on the first day until the fourth day of menstruation). The participant self‐reported VAS. Secondary Menstruation bleeding (number of pad consumption, time point was the first day to the fifth day of menstruation); mean number of mefenamic capsule 250 mg usage; satisfaction with the drugs (questionnaire).
Notes	“Twenty students (70%) in the study group avoided trying this protocol because fennel essence had a bad taste and mefenamic was more comfortable to use” Comment: it is unclear what this means. The study author responded by personal communication, and it appears that 70% of participants did not want to continue using fennel after completion of the study due to the taste
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	“Every 18‐25‑year‑old student who suffered from primary dysmenorrhoea with moderate to severe intensity was randomly assigned to each of the two study groups by use of a random number table.”
Allocation concealment (selection bias)	Unclear risk	Comment: the study authors did not describe allocation concealment methods.
Blinding (performance bias and detection bias) All outcomes	High risk	“oral fennel drop”. Comment: blinding was not mentioned. In addition, it is not possible to blind the participant to treatment (liquid forms (drop) versus capsule).
Incomplete outcome data (attrition bias) All outcomes	Low risk	“Sixty college students suffering from primary dysmenorrhoea were randomly assigned to two groups”. “Twenty‑nine students in the study group and 30 students in the control group were followed up. One student discontinued the trial due to malodor and bad taste of fennel drop.” Comment: the dropout rate was 3.33% (1/30).
Selective reporting (reporting bias)	Unclear risk	Comment: the study authors did not prespecify adverse events as an outcome.
Other bias	Low risk	Comment: we did not identify any other potential sources of bias.