Other
Rx only
Absorption
Absolute bioavailability for the subcutaneous and intramuscular route have not been determined; however, no difference was observed in dihydroergotamine bioavailability from intramuscular and subcutaneous doses.
Dihydroergotamine mesylate is poorly bioavailable following oral administration.
Distribution
Dihydroergotamine mesylate is 93% plasma protein bound. The apparent steady-state volume of distribution is approximately 800 liters.
Metabolism
Four dihydroergotamine mesylate metabolites have been identified in human plasma following oral administration. The major metabolite, 8´-β-hydroxydihydroergotamine, exhibits affinity equivalent to its parent for adrenergic and 5-HT receptors and demonstrates equivalent potency in several venoconstrictor activity models, in vivo and in vitro. The other metabolites, (i.e., dihydrolysergic acid, dihydrolysergic amide) and a metabolite formed by oxidative opening of the proline ring are of minor importance. Following nasal administration, total metabolites represent only 20% to 30% of plasma AUC. Quantitative pharmacokinetic characterization of the four metabolites has not been performed.
Excretion
The major excretory route of dihydroergotamine is via the bile in the feces. The total body clearance is 1.5 L/min which reflects mainly hepatic clearance. Only 6% to 7% of unchanged dihydroergotamine is excreted in the urine after intramuscular injection. The renal clearance (0.1 L/min) is unaffected by the route of dihydroergotamine administration. The decline of plasma dihydroergotamine after intramuscular or intravenous administration is multi-exponential with a terminal half-life of about 9 hours.
Subpopulations
No studies have been conducted on the effect of renal or hepatic impairment, gender, race, or ethnicity on dihydroergotamine pharmacokinetics. Dihydroergotamine Mesylate Injection, USP is contraindicated in patients with severely impaired hepatic or renal function (see CONTRAINDICATIONS).
Interactions
Pharmacokinetic interactions have been reported in patients treated orally with other ergot alkaloids (e.g., increased levels of ergotamine) and macrolide antibiotics, principally troleandomycin, presumably due to inhibition of cytochrome P4503A metabolism of the alkaloids by troleandomycin.
Dihydroergotamine has also been shown to be an inhibitor of cytochrome P4503A catalyzed reactions and rare reports of ergotism have been obtained from patients treated with dihydroergotamine and macrolide antibiotics (e.g., troleandomycin, clarithromycin, erythromycin), and in patients treated with dihydroergotamine and protease inhibitors (e.g., ritonavir), presumably due to inhibition of cytochrome P4503A metabolism of ergotamine (see CONTRAINDICATIONS). No pharmacokinetic interactions involving other cytochrome P450 isoenzymes are known.
CYP3A4 Inhibitors (e.g., Macrolide Antibiotics and Protease Inhibitors) (see CONTRAINDICATIONSand WARNINGS)
Risk Summary
Available data from published literature indicated an increased risk of preterm delivery with Dihydroergotamine Mesylate Injection, USP use during pregnancy. Avoid use of Dihydroergotamine Mesylate Injection, USP during pregnancy (see WARNINGS). Data collected over decades have shown no increased risk of major birth defects or miscarriage with the use of dihydroergotamine mesylate during pregnancy.
In animal reproduction studies, adverse effects on development were observed following intranasal administration of dihydroergotamine mesylate during pregnancy (decreased fetal body weight and/or skeletal ossification) in rats and rabbits or during pregnancy and lactation in rats (decreased body weight and impaired reproductive function in the offspring) at doses that were not associated with maternal toxicity (see Data).
The estimated rate of major birth defects (2.2% to 2.9%) and miscarriage (17%) among deliveries to women with migraine are similar to rates reported in women without migraine. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriages in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.
Data
Animal Data
Intranasal administration of dihydroergotamine mesylate to pregnant rats throughout the period of organogenesis resulted in decreased fetal body weight and/or skeletal ossification at doses of 0.16 mg/day and greater. A no-effect level for adverse effects on embryofetal development was not identified in rats. Intranasal administration of dihydroergotamine mesylate to pregnant rabbits throughout organogenesis resulted in decreased skeletal ossification of 3.6 mg/day. The no-effect dose for adverse effects on embryofetal development in rabbits was 1.2 mg/day.
Intranasal administration of dihydroergotamine mesylate to female rats throughout pregnancy and lactation resulted in decreased body weight and impaired reproductive function (decreased mating indices) in the offspring at doses of 0.16 mg/day or greater. A no-effect dose for adverse effects on pre- and postnatal development in rats was not established. Effects on offspring development occurred at doses below those that produced evidence of maternal toxicity in these studies.
Dihydroergotamine-induced intrauterine growth retardation has been attributed to reduced uteroplacental blood flow resulting from prolonged vasoconstriction of the uterine vessels and/or increased myometrial tone.