Low biological availability of ergotamine tartrate after oral dosing in cluster headache

An attempt was made to determine the plasma ergotamine concentrations in nine male patients with cluster headache 15-600 min after oral therapeutic doses of ergotamine tartrate (Cafergot). Some of the patients were studied twice. Five patients received a constant dose of 2-4 mg daily for at least seven days. Four patients were given 1 mg five times on one day and three patients a single oral dose of 2 mg. Ergotamine was determined by means of high performance liquid chromatography with fluorescence detection--a new highly sensitive, specific method, the detection limit of which is less than 100 pg/ml for ergotamine. Ergotamine tartrate was not discovered in any of the plasma samples. In one patient ergotamine could not be detected in the cerebrospinal fluid one hour after a single oral dose of 2 mg. The oral biological availability is less than 1%, which is the maximal available fraction of unchanged ergotamine after oral administration. A clinical benefit was observed in several of our patients. These effects of the drug may be because of active metabolites being formed and/or to high affinity of ergotamine to cranial vessels.