Systemic availability of ergotamine tartrate after oral, rectal and intramuscular administration.
Plasma ergotamine levels were measured in 33 volunteers (subgroups 11, 12 and 10) after a single dose of ergotamine administered by various routes. Ergotamine tartrate was given in doses normally used in the treatment of acute migraine--2.0 mg orally, 2.0 mg combined with 100 mg caffeine rectally and 0.5 mg i.m. Plasma ergotamine concentrations were determined by radioimmunoassay. The highest and longest lasting levels were found after i.m. administration, the peak concentration being 1.94 +/- 0.34 (SEM) ng/ml at 1/2 h. The corresponding maximum concentrations after oral and rectal administration were 0.36 +/- 0.08 ng/ml at 2 h and 0.42 +/- 0.09 ng/ml at 1 h. In most of the subjects the plasma ergotamine level began to rise again at 24 to 48 h. The cause of the elevation is not known but it might favour possible accumulation of the drug. Absorption from suppositories was at least as good as after oral administration and the former route may therefore be advantageous for migraine patients in whom nausea and vomiting during an attack may prevent efficient oral medication.