Zolmitriptan (Page 4 of 7)

10 OVERDOSAGE

There is no experience with acute overdose. Clinical study subjects receiving single 50 mg oral doses of zolmitriptan commonly experienced sedation.

The elimination half-life of zolmitriptan is 3 hours [see Clinical Pharmacology (12.1) ] and therefore monitoring of patients after overdose with zolmitriptan should continue for at least 15 hours or while symptoms or signs persist.

There is no specific antidote to zolmitriptan. In cases of severe intoxication, intensive care procedures are recommended, including establishing and maintaining a patent airway, ensuring adequate oxygenation and ventilation, and monitoring and support of the cardiovascular system.

It is unknown what effect hemodialysis or peritoneal dialysis has on the plasma concentrations of zolmitriptan.

11 DESCRIPTION

Zolmitriptan Nasal Spray, USP contains zolmitriptan, which is a selective 5-hydroxytryptamine _1B/1D (5-HT_1B/1D ) receptor agonist. Zolmitriptan is chemically designated as (S)-4-[[3-[2-(dimethylamino)ethyl]-1H-indol-5-yl]methyl]-2-oxazolidinone and has the following chemical structure:

The empirical formula is C₁₆ H₂₁ N₃ O₂ , representing a molecular weight of 287.36. Zolmitriptan is a white to almost white powder that is readily soluble in water. Zolmitriptan Nasal Spray is supplied as a clear to pale yellow solution of zolmitriptan, buffered to a pH 5.0. Each Zolmitriptan Nasal Spray contains 2.5 mg or 5 mg of zolmitriptan in a 100-μL unit dose aqueous buffered solution containing citric acid, anhydrous, USP, disodium phosphate dodecahydrate USP, benzalkonium chloride solution NF and purified water USP.

Zolmitriptan Nasal Spray is hypertonic. The osmolarity of Zolmitriptan Nasal Spray for 2.5 mg is 358 to 396 mOsmol, and for 5 mg is 411 to 455 mOsmol.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Zolmitriptan binds with high affinity to human recombinant 5-HT_1D and 5-HT₁ B receptors, and moderate affinity for 5-HT_1A receptors. The N-desmethyl metabolite also has high affinity for 5-HT_1B/1D and moderate affinity for 5-HT_1A receptors.

Current theories proposed to explain the etiology of migraine headache suggest that symptoms are due to local cranial vasodilatation and/or to the release of sensory neuropeptides (vasoactive intestinal peptide, substance P and calcitonin gene-related peptide) through nerve endings in the trigeminal system. The therapeutic activity of zolmitriptan for the treatment of migraine headache is thought to be due to the agonist effects at the 5-HT_1B/1D receptors on intracranial blood vessels (including the arterio-venous anastomoses) and sensory nerves of the trigeminal system which result in cranial vessel constriction and inhibition of pro-inflammatory neuropeptide release.

12.3 Pharmacokinetics

Absorption, Distribution, Metabolism, and Excretion

Absorption

Zolmitriptan nasal spray is rapidly absorbed via the nasopharynx as detected in a Photon Emission Tomography (PET) study using ¹¹ C zolmitriptan. The mean relative bioavailability of the nasal spray formulation is 102%, compared with the oral tablet. Zolmitriptan was detected in plasma by 5 minutes and peak plasma concentration generally was achieved by 3 hours. The time at which maximum plasma concentrations were observed was similar after single (1 day) or multiple (4 days) nasal dosing. Plasma concentrations of zolmitriptan are sustained for 4 to 6 hours after dosing. Zolmitriptan and its active N-desmethyl metabolite display linear kinetics after single or multiple doses of zolmitriptan nasal spray over the dose range of 0.1 to 10 mg.

The pharmacokinetics of the N-desmethyl metabolite are similar to that of zolmitriptan for all nasal spray dosages. The N-desmethyl metabolite is detected in plasma by 15 minutes and peak plasma concentration is generally achieved by 3 hours after administration.

Food has no significant effect on the bioavailability of zolmitriptan.

Distribution

Plasma protein binding of zolmitriptan is 25% over the concentration range of 10-1000 ng/mL. The mean apparent volume of distribution for zolmitriptan nasal spray formulation is 8.4 L/kg.

Metabolism

Zolmitriptan is converted to an active N-desmethyl metabolite such that the metabolite concentrations are about two-thirds that of zolmitriptan. Because the 5HT_1B/1D potency of the metabolite is 2 to 6 times that of the parent compound, the metabolite may contribute a substantial portion of the overall effect after zolmitriptan administration.

Excretion

The mean elimination half-life for zolmitriptan and N-desmethyl metabolite following single or multiple nasal spray administration are approximately 3 hours, similar to the half-life values seen after oral tablet administration.

In a study with orally administered zolmitriptan, total radioactivity recovered in urine and feces was 65% and 30% of the administered dose, respectively. In urine, unchanged zolmitriptan and N-desmethyl metabolite accounted for 8% and 4% of the dose, respectively, whereas the inactive indole acetic acid and N-oxide metabolites accounted for 31% and 7% of the dose, respectively.

Mean total plasma clearance for zolmitriptan nasal spray is 25.9 mL/min/kg, of which one-sixth is renal clearance. The renal clearance is greater than the glomerular filtration rate suggesting renal tubular secretion.

Specific Populations

Age:

The pharmacokinetics of orally administered zolmitriptan in healthy elderly non-migraineur volunteers (age 65-76 yrs) was similar to those in younger non-migraineur volunteers (age 18-39 yrs).

Sex:

Mean plasma concentrations of orally administered zolmitriptan were up to 1.5-fold higher in females than males.

Race:

There are no significant differences in the pharmacokinetics of orally administered zolmitriptan in Japanese and Caucasians.

Renal Impairment:

The effect of renal impairment on the pharmacokinetics of zolmitriptan nasal spray has not been evaluated. After orally dosing zolmitriptan, renal clearance was reduced by 25% in patients with severe renal impairment (Clcr ≥ 5 ≤ 25 mL/min) compared with the normal group (Clcr ≥ 70 mL/min); no significant change in clearance was observed in the moderately renally impaired group (Clcr ≥ 26 ≤ 50 mL/min).

Hepatic Impairment:

The effect of hepatic disease on the pharmacokinetics of zolmitriptan nasal spray has not been evaluated. In patients with severe hepatic impairment, the mean C_max , T_max , and AUC of zolmitriptan dosed orally were increased 1.5-fold, 2-fold (2 vs. 4 hours), and 3-fold, respectively, compared to subjects with normal hepatic function. Seven out of 27 patients experienced 20 to 80 mm Hg elevations in systolic and/or diastolic blood pressure after a 10 mg zolmitriptan dose [see Dosage and Administration (2.2) and Use in Specific Populations (8.6) ].

Hypertensive Patients:

No differences in the pharmacokinetics of oral zolmitriptan or its effects on blood pressure were seen in mild to moderate hypertensive volunteers compared with normotensive controls.

Drug Interactions

All drug interaction studies were performed in healthy volunteers using a single 10 mg dose of zolmitriptan and a single dose of the other drug except where otherwise noted. Eight drug interaction studies have been performed with zolmitriptan tablets and one study (xylometazoline) was performed with nasal spray.

Xylometazoline:

An in vivo drug interaction study with zolmitriptan nasal spray indicated that 1 spray (100 μL dose) of xylometazoline (0.1% w/v), a decongestant, administered 30 minutes prior to a 5 mg nasal dose of zolmitriptan did not alter the pharmacokinetics of zolmitriptan.

Fluoxetine:

The pharmacokinetics of zolmitriptan, as well as its effect on blood pressure, were unaffected by 4 weeks of pre-treatment with oral fluoxetine (20 mg/day).

MAO Inhibitors:

Following one week of administration of moclobemide (150 mg twice-daily), a specific MAO-A inhibitor, there was an increase of about 25% in both C_max and AUC for zolmitriptan and a 3-fold increase in the C_max and AUC of the active N-desmethyl metabolite of zolmitriptan [see Contraindications (4) and Drug Interactions (7.2)].

Selegiline, a selective MAO-B inhibitor, at a dose of 10 mg/day for 1 week, had no effect on the pharmacokinetics of zolmitriptan and its metabolite.

Propranolol:

C_max and AUC of zolmitriptan increased 1.5-fold after one week of dosing with propranolol (160 mg/day). C_max and AUC of the N-desmethyl metabolite were reduced by 30% and 15%, respectively. There were no interactive effects on blood pressure or pulse rate following administration of propranolol with zolmitriptan.

Acetaminophen:

A single 1g dose of acetaminophen does not alter the pharmacokinetics of zolmitriptan and its N-desmethyl metabolite. However, zolmitriptan delayed the T_max of acetaminophen by one hour.

Metoclopramide:

A single 10 mg dose of metoclopramide had no effect on the pharmacokinetics of zolmitriptan or its metabolites.

Oral Contraceptives:

Retrospective analysis of pharmacokinetic data across studies indicated that mean C_max and AUC of zolmitriptan were 30% and 50% higher, respectively, and T_max was delayed by one-half hour in females taking oral contraceptives compared to females not taking oral contraceptives. The effect of zolmitriptan on the pharmacokinetics of oral contraceptives has not been studied.

Cimetidine:

Following the administration of cimetidine, the half-life and AUC of a 5 mg dose of zolmitriptan and its active metabolite were approximately doubled. A dosage adjustment is therefore required [see Drug Interactions (7.4) ].