The kinetics of ergotamine has been investigated in migrainous patients using a new, specific, sensitive HPLC assay (detection limit 100 pg/ml plasma). 10 patients were given ergotamine tartrate 0.5 mg i.v. and 5 of them received the same dose i.m. 2-3 weeks later. Blood samples were collected for up to 54 h following administration and the plasma concentration were analysed. After intravenous administration the plasma ergotamine declined rapidly, with and initial distribution half-life of 3 min followed by a mean terminal half-life of 1.86 h (range 90-155 min). The mean total plasma clearance was 11.0 ml kg-1 min-1, and the volume of distribution (Vd beta) was 1847.6 ml kg-1. Individual t1/2 beta showed a positive linear correlation with the individual Vd beta. The intramuscular absorption of ergotamine was rapid and maximum plasma levels were usually obtained 10 min following administration. The biological availability was incomplete and variable at 46.6% (range 28.3-60.8%).

1 Fifteen migraine patients were administered 2 mg ergotamine tartrate in a partial cross-over design as a single, oral tablet, rectal suppository and rectal solution. Eight of these patients were in a previous investigation given 0.5 mg ergotamine tartrate intravenously. The blood samples were taken up to 54 h after oral and suppository while it was followed for only 3 h after rectal solution. The chemical analysis was performed by applying h.p.l.c. method with a limit of sensitivity of 0.1 ng/ml ergotamine base in plasma.2 No ergotamine was detected in the blood samples after the oral route, whereas small and very variable quantities was found in blood after the rectal route. Regular calculation of bioavailability could therefore not be performed. An estimate of the maximal possible bioavailability was found to yield a mean value of 2% (tablets); 5% (suppositories) and 6% (rectal solution). Rectal solution elicited faster absorption and the extent of absorption was significantly higher (P < 0.05) than for the suppository.

Plasma levels and the vasoconstrictive effect of 1 mg ergotamine tartrate given as tablets or suppositories were compared. In a crossover study, eight male volunteers received tablets or suppositories containing ergotamine in a drug combination (Anervan) and, as a control, suppositories without ergotamine. Blood sampling and measurement of toe-arm systolic gradients with a strain-gauge technique were done for up to 6 h and again after 24 h and 48 h. Only 29 of 160 blood samples contained detectable (greater than 0.1 ng/ml) amounts of ergotamine, and kinetic comparison could not be performed. Only ergotamine-containing suppositories caused a significant (p less than 0.008) decrease in toe-arm systolic gradient which was significantly different (p less than 0.003) from the effects of ergotamine tablets and control suppositories. Rectal ergotamine is thus more biologically active, for the factor used, than oral ergotamine. We suggest that a rectal dose of 1 mg ergotamine tartrate should be tried as the initial dose in the treatment of migraine attacks.

We gratefully acknowledge the co-operation of the surgical and gynaecological services