Letters to the Editor

Melatonin as a probable cause of diarrhoea was advised to stop taking it. Symptoms disappeared completely. When the patient herself decided to restart taking the same dose of melatonin the clinical symptoms reappeared. Subsequently she reduced her melatonin intake to 1.8 mg per day, which controlled the insomnia with no side effects.

Key words: Diarrhoea. Melatonin. Sleep disorders. Insomnia. Discussion

Melatonin is a hormone produced by the pineal gland and the enterochromaffin cells. (1,2). Its role in sleep regulation and the circadian rhythm is known (1,3). It is mainly prescribed for Dear Editor, treating jet lag and sleep disorders. Its potential use for treating gastro-oesophageal reflux disease, irritable bowel syndrome and Melatonin in dosages of less than 2 mg can be bought over the inflammatory bowel disease is currently being studied (1-5). counter in Spain. This high degree of accessibility emphasizes Since it was considered to be a prescribed drug, the marketing the need to study its safety profile. of melatonin was not authorized in Spain until 2009 when the European Union Court of Justice established that products with less than 2 mg dose could be sold without a prescription. The Case report most common documented side effects include headache, diz- ziness, nausea and drowsiness (6). In previous cases patients A 49 year old woman presented with diarrhoea lasting for reported nausea, vomiting, dysgeusia, abdominal pain, abnor- 3 weeks with 3-4 liquid bowel movements per day, with abun- mal stools and diarrhoea. However, there are no reported cas- dant bowel sounds. She had no pathologic findings in her stools, es of diarrhoea specifically caused by melatonin and neither abdominal pain, rectal tenesmus or fever. There was some weight is it mentioned in extensive studies on sleep disorders (6). In loss (2 kg) but no lack of appetite or nocturnal episodes. Her this case, melatonin is associated with the probable origin of primary care physician had prescribed loperamide 1 mg every diarrhoea. There is a temporal connection between the onset of 8 hours to control the diarrhoea. The patient indicated that the treatment, whilst symptoms disappeared when it was suspended onset of symptoms began after taking an herbal product for and reappeared when restarted, thereby ruling out other possi- insomnia, and that she was not using other drugs. Tests, which ble causes. Although the mechanism of diarrhoea is unknown, were carried out, included blood count, liver and renal function our case suggests a dose dependent effect. Conversely, a study shows increased colonic transit time in healthy volunteers taking profile, thyroid stimulating hormone, vitamin B12, folate, eryth- rocyte sedimentation rate, C-reactive protein, immunoglobulin A, melatonin at 3 mg doses (7). anti-endomysial and tissue transglutaminase IgA, stool culture, This case reveals that melatonin is a previously unpublished parasites in stool, and lactose intolerance. All test results were probable cause of diarrhoea. normal and therefore the focus was placed on investigating the composition of the product used for insomnia, which was melatonin 5 mg, taken daily. The onset of diarrhoea seems to have Israel Grilo-Bensusan, Elena Gómez-Delgado coincided with the use of melatonin and therefore the patient and Leonor Gómez-Regife 120 LETTERS TO THE EDITOR Rev Esp Enferm Dig (Madrid)

Hospital de Alta Resolución de Écija. Agencia Sanitaria 4. Chojnacki C, Wisniewska-Jarosinska M, Walecka-Kapica E, Klupinska G, Bajo Guadalquivir. Écija, Sevilla. Spain Jaworek J, Chojnacki J. Evaluation of melatonin effectiveness in the adju- vant treatment of ulcerative colitis. J Physiol Pharmacol 2011;62:327-34. 5. Chojnacki C, Walecka-Kapica E, Lokieć K, Pawłowicz M, Winczyk K, Chojnacki J, et al. Influence of melatonin on symptoms of irri- References table bowel syndrome in postmenopausal women. Endokrynol Pol 2013;64:114-20. 1. Brzezinski A. Melatonin in humans. N Engl J Med 1997;336:186-95. 6. Buscemi N, Vandermeer B, Hooton N, Pandya R, Tjosvold L, Hartling 2. Kandil TS, Mousa AA, El-Gendy AA, Abbas AM. The potential thera- L, et al. Efficacy and safety of exogenous melatonin for secondary peutic effect of melatonin in gastro-esophageal reflux disease. BMC sleep disorders and sleep disorders accompanying sleep restriction: Gastroenterol 2010;10: 7. meta-analysis. BMJ 2006;332:385-93. 3. Radwan P, Skrzydlo-Radomanska B, Radwan-Kwiatek K, Burak- 7. Lu WZ, Song GH, Gwee KA, Ho KY. The effects of melatonin on Czapiuk B, Strzemecka J. Is melatonin involved in the irritable bowel colonic transit time in normal controls and IBS patients. Dig Dis Sci syndrome? J Physiol Pharmacol 2009;60(Supl. 3):67-70. 2009;54:1087-93.

Rev Esp Enferm Dig 2015; 107 (2): 119-120