Ergotamine in plasma and CSF after i.m. and rectal administration to humans.

An attempt was made to study the kinetics of penetration of ergotamine across the blood-brain barrier. A single therapeutic dose of ergotamine was given to 18 hospitalized patients; eight patients received 0.5 mg i.m., three patients 4 mg rectally, and seven patients 2 mg rectally. Plasma samples were drawn between 0.25 and 72 h and one CSF sample was taken from each patient between 0.5 and 6.5 h after administration. The ergotamine concentrations were measured using a RIA method. The 0.5 mg intramuscular injection showed the highest plasma levels of ergotamine, with a mean peak concentration of 1.27 ng/ml reached at 0.5 h. The 4 mg rectal administration resulted in mean plasma ergotamine levels of 0.44 ng/ml in the time interval of 0.75-2 h. The 2 mg ergotamine rectally resulted in mean plasma levels of 0.15-0.17 ng/ml 1-8 h after administration of ergotamine. Neither the plasma samples taken after 10 h nor the CSF samples had ergotamine concentrations above the detection limit of the RIA method (0.1 ng ergotamine/ml).