Lf. Lacey et al., SINGLE-DOSE PHARMACOKINETICS OF SUMATRIPTAN IN HEALTHY-VOLUNTEERS, European Journal of Clinical Pharmacology, 47(6), 1995, pp. 543-548
Sumatriptan is classified as a vascular 5HT(1) receptor agonist and is
effective in the acute treatment of migraine and cluster headache. Su
matriptan is available as an injection for subcutaneous administration
and as a tablet for oral administration. The pharmacokinetics of suma
triptan differ depending on the route of administration. The mean subc
utaneous bioavilability is 96% compared to 14% for the oral tablet. Th
e lower bioavailability following oral administration is due mainly to
presystemic metabolism. The inter-subject. variability in plasma suma
triptan concentrations is greater following oral administration and a
faster rate of absorption of drug into the systemic circulation is ach
ieved following subcutaneous dosing, The pharmacokinetics of sumatript
an are linear up to a subcutaneous dose of 16 mg. Following oral dosin
g up to 400 mg, the pharmacokinetics are also linear, with the excepti
on of rate of absorption, as indicated by a dose dependent increase in
time to peak concentration. Sumatriptan is a highly cleared compound
that is eliminated from the body primarily by metabolism to the pharma
cologically inactive indoleacetic acid analogue. Both sumatriptan and
its metabolite are excreted in the urine. Although the renal clearance
of sumatriptan is only 20% of the total clearance, it exceeds the glo
merular filtration rate, indicating that sumatriptan undergoes active
renal tubular secretion. Sumatriptan has a large apparent volume of di
stribution (1701) and an elimination half-life of 2 h. Oral doses of s
umatriptan were administered as a solution of dispersible tablets and
subcutaneous dosing was by injection into the arm. In clinical practic
e, sumatriptan is administered as a film coated tablet or by subcutane
ous injection into the thigh.