Dysmenorrhea is one of the most prevalent disorders women suffer. More than 50% of female individuals suffer from mild pain during menstruation, but 10% of them are bedridden for 1-3 days per month. Dysmenorrhea has adverse effects on social relations, it can affect school and work productivity and cause financial loss. Dysmenorrhea is categorized as primary and secondary. In the primary type, there exists no diagnosable pelvic disorder.
In Iranian Traditional Medicine, fennel has been used as a carminative, diuretic, lithotriptic and galactagogue agent. Furthermore, based on the results of recent studies, the active ingredients of fennel have estrogenic, analgesic, inti-inflammatory, antioxidant and hepatoprotective properties.
To evaluate the pharmacologic effects of fennel on contractions of rat’s isolated uterus and calculation of LD50 in rats, oxytocin (0.1, 1, 10 mu/ml) and prostaglandin E2 (5×10-5 M) were used to induce muscle contractions. Various doses of fennel essential oil significantly reduced the severity of contractions induced by oxytocin and prostaglandin E2 (25, 50 μg/ml for oxytocin and 10, 25 μg/ml for prostaglandin E2, respectively). Furthermore, fennel essential oil reduced the frequency of contractions induced by prostaglandin E2 (and not the frequency of contractions induced by oxytocin). In this study, the LD50 calculated using moving average method equaled 1236 mg/kg. In what follows, the results of several clinical trials in relation to the effectiveness of fennel essential oil is presented:
- To compare the effect of sweet fennel with mefenamic acid in treatment of primary dysmenorrhea, 30 women aging 15 to 24, who suffered from moderate to severe primary dysmenorrhea, were studied during 3 menstrual cycles. In the first cycle, no medication was administered (control cycle), in the second, the patients were administered mefenamic acid (350 mg every 6 hours), and in the third, they received fennel essential oil 2% (25 drops every 4 hours). The results of this study showed that in comparison to the control group, both medications effectively eradicated dysmenorrhea (p<0.001). The average time for the onset of action was 67.5±46.06 minutes for mefenamic acid and 75±48.9 minutes for fennel; the difference was not statistically significant (p=0.57). In the second and third days of menstruation, mefenamic acid exhibited stronger effects compared to fennel (p<0.05). Nonetheless, there existed no significant difference between the two drugs in the other days of menstruation. No adverse reaction was reported with mefenamic acid. The researchers concluded that fennel can be used as a safe and effective medication for treatment of primary dysmenorrhea.
- In a placebo-controlled crossover double-blind clinical trial, 60 single female students of Tehran University dormitory aging 17-25, who suffered from dysmenorrhea, were studied. The severity of the patients’ dysmenorrhea was evaluated as 2nd or 3rd degree according to Andersch and Milsom index and they experienced pain in all or majority of cycles. After examination, sonography and confirmation of primary dysmenorrhea, the patients were randomly divided into 6 groups (as random arrangements of letters A, B and C) and each patient was studied for 3 cycles. In this study, drops containing 1% and 2% fennel essential oil were used, so that the patient would take 40 drops as soon as pain was felt and to repeat every 4 hours if needed. In case no reduction in pain was evident within 2 hours after taking the test medication and the pain was unbearable, the patient was allowed to take her conventional painkiller and register this in her assigned form. Based on the results of this study, the researchers came to the conclusion that the 1% and 2% fennel essential oil drops alleviate dysmenorrhea in 52.8% and 67.4% of individuals respectively, while causing relative improvement in 37.2% and 28.6%; these results are almost comparable with the effect of non-steroidal anti-inflammatory drugs (NSAIDs).
- To compare the effect of ibuprofen tablet and fennel essential oil on primary dysmenorrhea, in a clinical study, 120 high school students suffering from moderate to severe dysmenorrhea were randomly selected from 4 different high schools in the city of Mashhad. The severity of their dysmenorrhea was evaluated using Verbal Multidimensional Scoring system. They were monitored for one cycle (control cycle) and filled out form number one. In the second and third cycles, half of the individuals were administered ibuprofen tablet (400 mg, taken orally every 4-8 hours depending on their need) and the other half were administered 2% fennel essential oil drops (20-30 drops every 4-8 hours depending on their need); the treated individuals filled out two sets of forms in these two cycles. Based on the results of the analyzed data for 100 patients, the 2% fennel essential oil drop caused a reduction in the severity (p<0.001) and duration (p=0.000) of dysmenorrhea; this reduction had no statistically significant difference with the group that had taken ibuprofen tablets and the both medications equally alleviated dysmenorrhea. The need for taking additional analgesic was similar in both groups (p=0.148). Also, taking the 2% fennel essential oil drop caused a reduction in the duration of bleeding (p=0.045). There was no significant difference in the amount of bleeding before and after taking the 2% fennel essential oil drop (p=0.308), and administration of fennel essential oil did not affect the amount of bleeding. In the group taking ibuprofen, reduction in bleeding was evident (p=0.038). There was no statistically significant difference in patient satisfaction between the two groups (p=NS). The researchers came to the conclusion that in the patients who prefer to take herbal medications, or individuals for whom NSAIDs are contraindicated, 2% fennel essential oil drop can effectively alleviate primary dysmenorrhea and can be considered a suitable substitute for ibuprofen tablet, despite the fact that no definitive mechanism of action is yet presented for this medicinal herb.
- In a prospective clinical trial, 60 students with a history of Premenstrual Syndrome (PMS) were selected and evaluated through 5 cycles (first cycle: no medication, control; second and third: fennel; fourth and fifth: chamomile). After each cycle, the studied group was evaluated by filling out questionnaires including 16 symptoms of PMS and dysmenorrhea. According to the results of this study, in comparison to the placebo group, out of the 16 symptoms in the questionnaire, there was a significant reduction in the fennel and chamomile groups only in the case of the three symptoms: abdominal and pelvic pain, fatigue and lethargy and depression or frustration (p<0.05). In the case of other symptoms, although their severity was less in the chamomile and fennel cycles, this difference with the control cycle was not significant. The researchers came to the conclusion that administration of fennel and chamomile has statically significant effect only upon 3 symptoms of PMS and dysmenorrhea; chamomile is more effective upon abdominal and pelvic pain, depression and frustration, and fennel more on fatigue and lethargy.
Fennel has also been used in cases of amenorrhea and to increase milk production in nursing mothers.