PLATELET AGGREGATION IN RESPONSE TO 5-HT IN MIGRAINE PATIENTS TAKING ORAL CONTRACEPTIVES

Abstract

About 1 in 4 of unselected new female patients seen by one of us (E.H.) at a migraine clinic has migraine attacks associated with taking oral contraception (OC). In some such patients attacks began after OC was started (group 1) and in others attacks have become more frequent and severe since patient began to take OCs (group 2). The fact that headaches can occur as a side effect of the was recognized in 1962. Other workers have reported changes in platelet behavior in patients on OCs. We found that platelets from patients with severe classical migraine showed a significant increase in aggregation in response to 5-hydroxy-tryptamine (5-HT). We therefore decided to investigate rate and extent of platelet aggregation in response to 5-HT in 2 groups of migraine patients on pill. All patients were taking estrogen-containing preparations but had taken no other drugs during 10 days before blood samples were taken. In addition we tested platelet aggregation using adenosine diphosphate (ADP) noradrenaline and adrenaline. Migraine was defined as a severe recurrent headache ususally affecting 1 side of head more than other and often associated with vomiting. Prodromal symptoms usually visual were mentioned by some patients. The studies were repeated 4-6 months after patients had stopped taking pill by which time there had been a marked improvement in symptoms in every case. This improvement was gradual and usually spread over several weeks or even months. Our results to date show significant differences in 2 groups (seen in table). Group 1 patients (no migraine attacks before starting pill) showed a significant reduction in extent of platelet aggregation induced by 5-HT after they stopped taking pill (P<0.05). In addition group 1 patients off pill showed a significant reduction in extent and rate of platelet aggregation with 5-HT when compared with group 2 also off pill (P<0.05). There was no significant changes in platelet aggregation induced by ADP noradrenaline and adrenaline. Had we considered patients with increasingly severe migraine on pill as a single group significant changes in platelet behavior would have been overlooked. Our findings indicate that pill can produce changes in platelet behavior which are found in nonpill-taking migraine patients. Patients starting OC should be questioned both about their own and their close family history of migraine. An awareness of relation between platelet changes on pill and migraine is clinically important. (full text)