From Dr M. Griffiths, MRPharmS
SIR,-A pain in the head is investigated by consultants in neurology and a pain in the gut leads to the gastroenterology department. There is a tendency to forget that the same blood, with its constituents, is racing round the whole body and affecting any susceptible organs. This can result in a collection of various symptoms which is best considered as a "holistic" disease. A good example of this is migraine, where swinging levels of plasma 5-HT can produce a variety of effects throughout the body.
A migraine patient can have few or many symptoms and different combinations with each attack. For example, only 10 to 20 per cent have visual disturbance before the headache and this "aura" is not always followed by a headache. In many people, the intestinal effects predominate, when initial looseness due to high 5-HT is followed by little colon movement, with pain, discomfort, bloating, nausea and sometimes water retention when 5-HT levels are low for as long as one to three days. When 5-HT levels return to normal, the body begins to get rid of the backlog of faeces with several visits to the toilet in one day.
Most patients and indeed health professionals think that migraine is a headache with other side effects. Abdominal migraine, with its alternating diarrhoea and constipation, does not fit very well into the medical pigeon-hole. It is accepted in children. But without or even with the headache in adults, it is quite likely to be diagnosed as irritable bowel syndrome. For example, in a survey by the Irish Migraine Association,1 respondents had a ratio of five women to one man, and 51 per cent had been diagnosed with IBS as well as migraine. This might have a bearing on the selection of women for the study on alosetron reported in The Pharmaceutical Journal of April 1 (p504), and the results may reflect the suggestion that migraine is really behind the diagnosis of IBS in many cases.
The 5-HT antagonist counteracted the stimulation of the gut by high plasma 5-HT levels but compounded the effects of the phase of low 5-HT, producing constipation in 30 per cent of patients in the trial. It is difficult to see how a continuous treatment could be effective in "alternating" IBS. The headline "Alosetron found to be effective for IBS" (PJ, April 1, p504) is hardly justified by the narrow selection of patient type and the high occurrence of constipation that can also be a major problem for many IBS sufferers.
Mary Griffiths
Macclesfield, Cheshire
| l. Migraine Action News. Migraine Action Association. January, 1999. |