The Effect of Fennel on Pain Relief in Primary Dysmenorrhea: A Systematic Review of Clinical Trials

Abstract

Abstract<br />Background and aims: Fennel is often advocated for primary dysmenorrhea. Whether this herb has a<br />real effect on pain relief is still a matter of debate in medicine. Therefore, this study was conducted to<br />evaluate the effect of fennel on primary dysmenorrhea.<br />Methods: This systematic review was conducted on clinical trials (non-randomized, randomized,<br />historical study with concurrent control) published in PubMed (MEDLINE), Web of Science, Scopus,<br />Cochrane Central Register of Controlled Trials (CENTRAL), ProQuest, and Persian databases (Magiran,<br />IranMedex, SID, Irandoc) regarding the effect of fennel on pain intensity in primary dysmenorrhea from<br />1990 to 2019. Nine studies met all inclusion criteria. Any clinical trials on young women with primary<br />dysmenorrhea were included in the study. Studies that used fennel plus other products investigated<br />fennel effect on premenstrual syndrome (PMS) and bleeding; studies without a control group and<br />nonclinical trials were excluded. In all studies, participants were young female university or high<br />school students. All of them had moderate to severe primary dysmenorrhea.<br />Results: In all of the studies except for one, fennel had been more effective than placebo in pain relief<br />(P < 0.01). Non-steroidal drugs had the same result as fennel for pain relief. However, in one study,<br />the difference between non-steroidal anti-inflammatory drugs (NSAIDs) and fennel in pain relief was<br />observed. Only one study reported increasing vaginal bleeding after fennel consumption in some<br />cases.<br />Conclusion: Collectively, these studies favored fennel over NSAID, other herbal drugs, and placebo.<br />But more investigation is needed to draw a firm conclusion.<br />Registration: PROSPERO - 42015023725