Clinical Pharmacokinetics of Almotriptan, a Serotonin 5-HT(1B/1D) Receptor Agonist for the Treatment of Migraine

The pharmacokinetics of almotriptan are linear over a range of oral doses up to 200mg in healthy volunteers. The compound has a half-life of approximately 3 hours. Almotriptan is well absorbed after oral administration and the mean absolute bioavailability is 69.1%. Maximal plasma concentrations are achieved between 1.5 and 4 hours after dose administration; however, within 1 hour after administration, plasma concentrations are approximately 68% of the value at 3 hours after administration. Food does not significantly affect almotriptan absorption. Almotriptan is not highly protein bound and is extensively distributed in the body. Approximately 50% of an almotriptan dose is excreted unchanged in the urine; this is the predominant single mechanism of elimination. Renal clearance is mediated, in part, through active tubular secretion, while the balance of the almotriptan dose is metabolised to inactive compounds. The predominant route of metabolism is via monoamine oxidase-A, and cytochrome P450 (CYP) mediated oxidation (via CYP3A4 and CYP2D6) occurs to a minor extent. Almotriptan clearance is moderately reduced in elderly subjects, but the magnitude of this effect does not warrant a dose reduction. Sex has no significant effect on almotriptan pharmacokinetics. Almotriptan pharmacokinetic parameters do not differ between adolescents and adults, and absorption is not affected during a migraine attack. As expected, renal dysfunction results in reduced clearance of almotriptan. Patients with moderate-to-severe renal dysfunction should use the lowest dose of almotriptan and the total daily dose should not exceed 12.5 mg. Similar dosage recommendations are valid for patients with hepatic impairment, based on the clearance mechanisms for almotriptan. Drug-drug interaction studies were conducted between almotriptan and the following compounds: fluoxetine, moclobemide, propranolol, verapamil and ketoconazole. No significant pharmacokinetic or pharmacodynamic interactions with almotriptan were observed for fluoxetine or propranolol. Almotriptan clearance was reduced, to a modest degree, by moclobemide and verapamil, which was consistent with the contribution of monoamine oxidase-A and CYP3A4 to the metabolic clearance of almotriptan. Although ketoconazole has a greater effect on almotriptan clearance than verapamil, no dosage adjustment is required when almotriptan is given with these drugs.