CLINICAL PHARMACOLOGY SECTION

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Zolmitriptan binds with high affinity to human recombinant 5-HT1D and 5-HT1B receptors, and moderate affinity for 5-HT1A receptors. The N-desmethyl metabolite also has high affinity for 5-HT1B/1D and moderate affinity for 5-HT1A receptors.

Migraines are likely 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-HT1B/1D receptors on intracranial blood vessels (including the arteriovenous 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 is well absorbed after oral administration for both zolmitriptan tablets and the zolmitriptan orally disintegrating tablets. Zolmitriptan displays linear kinetics over the dose range of 2.5 to 50 mg.

The AUC and Cmax of zolmitriptan are similar following administration of zolmitriptan tablets and zolmitriptan orally disintegrating tablets, but the Tmax is somewhat later with zolmitriptan orally disintegrating tablets, with a median Tmax of 3 hours for zolmitriptan orally disintegrating tablet compared with 1.5 hours for the zolmitriptan tablet. The AUC, Cmax, and Tmax for the active N-desmethyl metabolite are similar for the two formulations.

During a moderate to severe migraine attack, mean AUC0-4 and Cmax for zolmitriptan, dosed as a zolmitriptan tablet, were decreased by 40% and 25%, respectively, and mean Tmax was delayed by one-half hour compared to the same patients during a migraine free period.

Food has no significant effect on the bioavailability of zolmitriptan. No accumulation occurred on multiple dosing.

Distribution

Mean absolute bioavailability is approximately 40%. The mean apparent volume of distribution is 7 L/kg. Plasma protein binding of zolmitriptan is 25% over the concentration range of 10 to 1000 ng/mL.

Metabolism

Zolmitriptan is converted to an active N-desmethyl metabolite; the metabolite concentrations are about two-thirds that of zolmitriptan. Because the 5-HT1B/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

Total radioactivity recovered in urine and feces was 65% and 30% of the administered dose, respectively. About 8% of the dose was recovered in the urine as unchanged zolmitriptan. Indole acetic acid metabolite accounted for 31% of the dose, followed by N-oxide (7%) and N-desmethyl (4%) metabolites. The indole acetic acid and N-oxide metabolites are inactive.

Mean total plasma clearance is 31.5 mL/min/kg, of which one-sixth is renal clearance. The renal clearance is greater than the glomerular filtration rate suggesting renal tubular secretion.

Special Populations

Hepatic Impairment

In patients with severe hepatic impairment, the mean Cmax, Tmax, and AUC0-∞ of zolmitriptan 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 mmHg elevations in systolic and/or diastolic blood pressure after a 10 mg zolmitriptan dose. Adjust the zolmitriptan dose in patients with moderate or severe hepatic impairment [see Dosage and Administration (2.3) and Use in Specific Populations (8.6)].

Renal Impairment

Clearance of zolmitriptan was reduced by 25% in patients with severe renal impairment (Clcr > 5 < 25 mL/min) compared to subjects with normal renal function (Clcr > = 70 mL/min); no significant change in clearance was observed in patients with moderate renal impairment (Clcr > 26 < 50 mL/min).

Age

Zolmitriptan pharmacokinetics in healthy elderly non-migraineur volunteers (age 65 to 76 years) was similar to those in younger non-migraineur volunteers (age 18 to 39 years).

Sex

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

Race

Retrospective analysis of pharmacokinetic data between Japanese and Caucasians revealed no significant differences.

Hypertensive Patients

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

Drug Interaction Studies

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.

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 Cmax and AUC for zolmitriptan and a 3-fold increase in the Cmax and AUC of the active Ndesmethyl metabolite of zolmitriptan. MAO inhibitors are contraindicated in zolmitriptan-treated patients [see Contraindications (4), Warnings and Precautions (5.7), and Drug Interactions (7.2, 7.4)].

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.

Cimetidine

Following the administration of cimetidine, the half-life and AUC of zolmitriptan (5 mg dose), and its active metabolite, were approximately doubled [see Dosage and Administration (2.4122), Drug Interactions (7.5)].

Fluoxetine

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

Propranolol

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

Acetaminophen

A single 1 gram dose of acetaminophen did not alter the pharmacokinetics of zolmitriptan and its N-desmethyl metabolite. However, zolmitriptan administration delayed the Tmax 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 Cmax and AUC of zolmitriptan were increased by 30% and 50%, respectively, and Tmax was delayed by one-half hour in women taking oral contraceptives. The effect of zolmitriptan on the pharmacokinetics of oral contraceptives has not been studied.

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WARNINGS AND PRECAUTIONS SECTION

Highlight: * Myocardial Ischemia/Infarction, and Prinzmetal Angina : Perform cardiac evaluation in patients with multiple cardiovascular risk factors (5.1)

• Arrhythmias : Discontinue zolmitriptan if occurs (5.2)
• Chest/Throat/Neck/Jaw Pain, Tightness, and Pressure : Generally not associated with myocardial ischemia; evaluate for CAD in patients at high risk (5.3)
• Cerebral Hemorrhage, Subarachnoid Hemorrhage, and Stroke : Discontinue zolmitriptan if occurs (5.4)
• Gastrointestinal Ischemic Reactions and Peripheral Vasospastic Reactions : Discontinue zolmitriptan if occurs (5.5)
• Medication Overuse Headache : Detoxification may be necessary (5.6)
• Serotonin Syndrome : Discontinue zolmitriptan if occurs (5.7, 7.4)

5 WARNINGS AND PRECAUTIONS

5.1 Myocardial Ischemia, Myocardial Infarction, and Prinzmetal Angina

Zolmitriptan is contraindicated in patients with ischemic or vasospastic coronary artery disease (CAD). There have been rare reports of serious cardiac adverse reactions, including acute myocardial infarction, occurring within a few hours following administration of zolmitriptan. Some of these reactions occurred in patients without known CAD. 5-HT1 agonists including zolmitriptan may cause coronary artery vasospasm (Prinzmetal Angina), even in patients without a history of CAD.

Perform a cardiovascular evaluation in triptan-nave patients who have multiple cardiovascular risk factors (e.g., increased age, diabetes, hypertension, smoking, obesity, strong family history of CAD) prior to receiving zolmitriptan. Do not administer zolmitriptan if there is evidence of CAD or coronary artery vasospasm [see Contraindications (4)]. For patients with multiple cardiovascular risk factors who have a negative cardiovascular evaluation, consider administrating the first zolmitriptan dose in a medically-supervised setting and performing an electrocardiogram (ECG) immediately following zolmitriptan administration. For such patients, consider periodic cardiovascular evaluation in intermittent long-term users of zolmitriptan.

5.2 Arrhythmias

Life-threatening disturbances of cardiac rhythm including ventricular tachycardia and ventricular fibrillation leading to death have been reported within a few hours following the administration of 5-HT1 agonists. Discontinue zolmitriptan if these disturbances occur. Zolmitriptan is contraindicated in patients with Wolff-Parkinson-White syndrome or arrhythmias associated with other cardiac accessory conduction pathway disorders [see Contraindications (4)].

5.3 Chest, Throat, Neck and Jaw Pain/Tightness/Pressure

As with other 5-HT1 agonists, sensations of tightness, pain, and pressure in the chest, throat, neck, and jaw commonly occur after treatment with zolmitriptan and is usually non-cardiac in origin. However, perform a cardiac evaluation if these patients are at high cardiac risk. 5-HT1 agonists including zolmitriptan are contraindicated in patients with CAD or Prinzmetal's variant angina [see Contraindications (4)]

5.4 Cerebrovascular Events

Cerebral hemorrhage, subarachnoid hemorrhage, and stroke have occurred in patients treated with 5-HT1 agonists, and some have resulted in fatalities. In a number of cases, it appears possible that the cerebrovascular events were primary, the 5-HT1 agonist having been administered in the incorrect belief that the symptoms experienced were a consequence of migraine, when they were not.

As with other acute migraine therapies, before treating headaches in patients not previously diagnosed as migraineurs, and in migraineurs who present with symptoms atypical for migraine, exclude other potentially serious neurological conditions. Zolmitriptan is contraindicated in patients with a history of stroke or transient ischemic attack [see Contraindications (4)].

5.5 Other Vasospasm Reactions

5-HT1 agonists, including zolmitriptan, may cause non-coronary vasospastic reactions, such as peripheral vascular ischemia, gastrointestinal vascular ischemia and infarction (presenting with abdominal pain and bloody diarrhea), splenic infarction, and Raynaud's syndrome. In patients who experience symptoms or signs suggestive of a vasospastic reaction following the use of any 5-HT1 agonist, rule out a vasospastic reaction before receiving additional zolmitriptan doses [see Contraindications (4)].

Reports of transient and permanent blindness and significant partial vision loss have been reported with the use of 5-HT1 agonists. Since visual disorders may be part of a migraine attack, a causal relationship between these events and the use of 5-HT1 agonists have not been clearly established.

5.6 Medication Overuse Headache

Overuse of acute migraine drugs (e.g., ergotamine, triptans, opioids, or a combination of drugs for 10 or more days per month) may lead to exacerbation of headache (medication overuse headache). Medication overuse headache may present as migraine-like daily headaches or as a marked increase in frequency of migraine attacks. Detoxification of patients, including withdrawal of the overused drugs, and treatment of withdrawal symptoms (which often includes a transient worsening of headache) may be necessary.

5.7 Serotonin Syndrome

Serotonin syndrome may occur with triptans, including zolmitriptan, particularly during coadministration with selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), and MAO inhibitors [see Drug Interactions (7.5)]. Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, coma), autonomic instability (e.g., tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g., hyperreflexia, incoordination), and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). The onset of symptoms usually rapidly occurs within minutes to hours of receiving a new or a greater dose of a serotonergic medication. Discontinue zolmitriptan if serotonin syndrome is suspected [see Drug Interactions (7.4)].

5.8 Increase in Blood Pressure

Significant elevations in systemic blood pressure have been reported in patients treated with 5-HT1 agonists including patients without a history of hypertension; very rarely, these increases in blood pressure have been associated with serious adverse reactions. In healthy subjects treated with 5 mg of zolmitriptan, an increase of 1 and 5 mmHg in the systolic and diastolic blood pressure, respectively, was seen. In a study of patients with moderate to severe liver impairment, 7 of 27 patients experienced 20 to 80 mmHg elevations in systolic and/or diastolic blood pressure after a dose of 10 mg of zolmitriptan.

As with all triptans, blood pressure should be monitored in zolmitriptan- treated patients. Zolmitriptan is contraindicated in patients with uncontrolled hypertension [see Contraindications (4)].

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USE IN SPECIFIC POPULATIONS SECTION

Highlight: Pregnancy: Based on animal data, may cause fetal harm (8.1)

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category C

There are no adequate and well- controlled studies in pregnant women; therefore, zolmitriptan should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. In reproductive toxicity studies in rats and rabbits, oral administration of zolmitriptan to pregnant animals resulted in embryolethality and fetal abnormalities (malformations and variations) at clinically relevant exposures.

When zolmitriptan was administered to pregnant rats during the period of organogenesis at oral doses of 100, 400, and 1200 mg/kg/day (plasma exposures (AUCs) ≈280, 1100, and 5000 times the human AUC at the maximum recommended human dose (MRHD) of 10 mg/day), there was a dose-related increase in embryolethality. A no-effect dose for embryolethality was not established. When zolmitriptan was administered to pregnant rabbits during the period of organogenesis at oral doses of 3, 10, and 30 mg/kg/day (plasma AUCs ≈1, 11, and 42 times the human AUC at the MRHD), there were increases in embryolethality and in fetal malformations and variations. The no-effect dose for adverse effects on embryo-fetal development was associated with a plasma AUC similar to that in humans at the MRHD. When female rats were given zolmitriptan during gestation, parturition, and lactation at oral doses of 25, 100, and 400 mg/kg/day (plasma AUCs ≈70, 280, and 1100 times that in human at the MRHD), an increased incidence of hydronephrosis was found in the offspring. The no-effect dose was associated with a plasma AUC ≈280 times that in humans at the MRHD.

8.3 Nursing Mothers

It is not known whether zolmitriptan is excreted in human milk. Because many drugs are excreted in human milk, and because of the potential for serious adverse reactions in nursing infants from zolmitriptan, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

In rats, oral dosing with zolmitriptan resulted in levels in milk up to 4 times higher than in plasma.

8.4 Pediatric Use

The safety and effectiveness in pediatric patients have not been established. Therefore, zolmitriptan is not recommended for use in patients under 18 years of age.

One randomized, placebo-controlled clinical trial of zolmitriptan tablets (2.5, 5 and 10 mg) evaluated 696 pediatric patients (aged 12 to 17 years) with migraines. This study did not demonstrate the efficacy of zolmitriptan compared to placebo in the treatment of migraine in adolescents. Adverse reactions in the adolescent patients treated with zolmitriptan were similar in nature and frequency to those reported in clinical trials in adults treated with zolmitriptan. Zolmitriptan has not been studied in pediatric patients less than 12 years old.

In the postmarketing experience with triptans, including zolmitriptan, there were no additional adverse reactions seen in pediatric patients that were not seen in adults.

8.5 Geriatric Use

Clinical studies of zolmitriptan did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

A cardiovascular evaluation is recommended for geriatric patients who have other cardiovascular risk factors (e.g., diabetes, hypertension, smoking, obesity, strong family history of coronary artery disease) prior to receiving zolmitriptan [see Warnings and Precautions (5.1)].

The pharmacokinetics of zolmitriptan were similar in geriatric patients (aged

65 years) compared to younger patients [see Clinical Pharmacology (12.3)].

8.6 Patients with Hepatic Impairment:

After oral zolmitriptan administration, zolmitriptan blood levels were increased in patients with moderate to severe hepatic impairment, and significant elevation in blood pressure was observed in some of these patients [see Warnings and Precautions (5.8)]. Therefore, adjust the zolmitriptan dose and administer with caution in patients with moderate or severe hepatic impairment [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)].

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