Amerge

Dosage Forms And Strengths

1-mg white tablets, D-shaped, film-coated, and debossed with “GX CE3”

2.5-mg green tablets, D-shaped, film-coated, and debossed with “GX CE5”

Storage And Handling

AMERGE tablets containing 1 mg and 2.5 mg of naratriptan (base) as the hydrochloride salt.

AMERGE tablets, 1 mg, are white, D-shaped, film-coated tablets debossed with “GX CE3” on one side in blister packs of 9 tablets (NDC 0173-0561-00).

AMERGE tablets, 2.5 mg, are green, D-shaped, film-coated tablets debossed with “GX CE5” on one side in blister packs of 9 tablets (NDC 0173-0562-00).

Store at controlled room temperature, 20° to 25°C (68° to 77°F).

GlaxoSmithKline, Research Triangle Park, NC 27709. Revised: August 2015

AMERGE® is indicated for the acute treatment of migraine with or without aura in adults.

Limitations Of Use

• Use only if a clear diagnosis of migraine has been established. If a patient has no response to the first migraine attack treated with AMERGE, reconsider the diagnosis of migraine before AMERGE is administered to treat any subsequent attacks.
• AMERGE is not indicated for the prevention of migraine attacks.
• Safety and effectiveness of AMERGE have not been established for cluster headache.

Dosing Information

The recommended dose of AMERGE is 1 mg or 2.5 mg.

If the migraine returns or if the patient has only partial response, the dose may be repeated once after 4 hours, for a maximum dose of 5 mg in a 24-hour period.

The safety of treating an average of more than 4 migraine attacks in a 30-day period has not been established.

Dosage Adjustment In Patients With Renal Impairment

AMERGE is contraindicated in patients with severe renal impairment (creatinine clearance: < 15 mL/min) because of decreased clearance of the drug.

In patients with mild to moderate renal impairment, the maximum daily dose should not exceed 2.5 mg over a 24-hour period and a 1-mg starting dose is recommended.

Dosage Adjustment In Patients With Hepatic Impairment

AMERGE is contraindicated in patients with severe hepatic impairment (Child-Pugh Grade C) because of decreased clearance.

In patients with mild or moderate hepatic impairment (Child-Pugh Grade A or B), the maximum daily dose should not exceed 2.5 mg over a 24-hour period and a 1-mg starting dose is recommended.

AMERGE is contraindicated in patients with:

• Ischemic coronary artery disease (CAD) (angina pectoris, history of myocardial infarction, or documented silent ischemia) or coronary artery vasospasm, including Prinzmetal's angina
• Wolff-Parkinson-White syndrome or arrhythmias associated with other cardiac accessory conduction pathway disorders
• History of stroke or transient ischemic attack (TIA) or history of hemiplegic or basilar migraine because such patients are at a higher risk of stroke
• Peripheral vascular disease
• Ischemic bowel disease
• Uncontrolled hypertension
• Recent use (i.e., within 24 hours) of another 5-HT1 agonist, ergotamine-containing medication, ergot-type medication (such as dihydroergotamine or methysergide)
• Hypersensitivity to AMERGE (angioedema and anaphylaxis seen)
• Severe renal or hepatic impairment

WARNINGS

Included as part of the PRECAUTIONS section.

PRECAUTIONS

Myocardial Ischemia, Myocardial Infarction, And Prinzmetal's Angina

AMERGE is contraindicated in patients with ischemic or vasospastic CAD. There have been rare reports of serious cardiac adverse reactions, including acute myocardial infarction, occurring within a few hours following administration of AMERGE. Some of these reactions occurred in patients without known CAD. AMERGE may cause coronary artery vasospasm (Prinzmetal's angina) even in patients without a history of CAD.

Perform a cardiovascular evaluation in triptan-naive patients who have multiple cardiovascular risk factors (e.g., increased age, diabetes, hypertension, smoking, obesity, strong family history of CAD) prior to receiving AMERGE. If there is evidence of CAD or coronary artery vasospasm, AMERGE is contraindicated. For patients with multiple cardiovascular risk factors who have a negative cardiovascular evaluation, consider administering the first dose of AMERGE in a medically supervised setting and performing an electrocardiogram (ECG) immediately following administration of AMERGE. For such patients, consider periodic cardiovascular evaluation in intermittent long-term users of AMERGE.

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 AMERGE if these disturbances occur. AMERGE is contraindicated in patients with Wolff-Parkinson-White syndrome or arrhythmias associated with other cardiac accessory conduction pathway disorders.

Chest, Throat, Neck, And/Or Jaw Pain/Tightness/Pressure

Sensations of tightness, pain, and pressure in the chest, throat, neck, and jaw commonly occur after treatment with AMERGE and are usually non-cardiac in origin. However, perform a cardiac evaluation if these patients are at high cardiac risk. 5-HT1 agonists, including AMERGE, are contraindicated in patients with CAD and those with Prinzmetal's variant angina.

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. Also, patients with migraine may be at increased risk of certain cerebrovascular events (e.g., stroke, hemorrhage, TIA). Discontinue AMERGE if a cerebrovascular event occurs.

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. AMERGE is contraindicated in patients with a history of stroke or TIA.

Other Vasospasm Reactions

AMERGE 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 non-coronary vasospasm reaction following the use of any 5-HT1 agonist, rule out a vasospastic reaction before receiving additional doses of AMERGE.

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.

Medication Overuse Headache

Overuse of acute migraine drugs (e.g., ergotamine, triptans, opioids, or combination of these 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.

Serotonin Syndrome

Serotonin syndrome may occur with AMERGE, particularly during co-administration with selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), and monoamine oxidase (MAO) inhibitors. 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 occurs within minutes to hours of receiving a new or a greater dose of a serotonergic medication. Discontinue AMERGE if serotonin syndrome is suspected.

Increase In Blood Pressure

Significant elevation in blood pressure, including hypertensive crisis with acute impairment of organ systems, has been reported on rare occasions in patients treated with 5-HT1 agonists, including patients without a history of hypertension. Monitor blood pressure in patients treated with AMERGE. AMERGE is contraindicated in patients with uncontrolled hypertension.

Anaphylactic/Anaphylactoid Reactions

There have been reports of anaphylaxis and anaphylactoid and hypersensitivity reactions, including angioedema, in patients receiving AMERGE. Such reactions can be life threatening or fatal. In general, anaphylactic reactions to drugs are more likely to occur in individuals with a history of sensitivity to multiple allergens. AMERGE is contraindicated in patients with a history of hypersensitivity reaction to AMERGE.

Patient Counseling Information

Advise the patient to read the FDA-approved patient labeling (PATIENT INFORMATION).

Risk of Myocardial Ischemia and/or Infarction, Prinzmetal's Angina, Other Vasospasm-Related Events, Arrhythmias, and Cerebrovascular Events

Inform patients that AMERGE may cause serious cardiovascular side effects such as myocardial infarction or stroke. Although serious cardiovascular events can occur without warning symptoms, patients should be alert for the signs and symptoms of chest pain, shortness of breath, irregular heartbeat, significant rise in blood pressure, weakness, and slurring of speech and should ask for medical advice if any indicative sign or symptoms are observed. Apprise patients of the importance of this follow-up.

Anaphylactic/Anaphylactoid Reactions

Inform patients that anaphylactic/anaphylactoid reactions have occurred in patients receiving AMERGE. Such reactions can be life threatening or fatal. In general, anaphylactic reactions to drugs are more likely to occur in individuals with a history of sensitivity to multiple allergens.

Concomitant Use with Other Triptans or Ergot Medications

Inform patients that use of AMERGE within 24 hours of another triptan or an ergot-type medication (including dihydroergotamine or methysergide) is contraindicated.

Serotonin Syndrome

Caution patients about the risk of serotonin syndrome with the use of AMERGE or other triptans, particularly during combined use with SSRIs, SNRIs, TCAs, and MAO inhibitors.

Medication Overuse Headache

Inform patients that use of acute migraine drugs for 10 or more days per month may lead to an exacerbation of headache and encourage patients to record headache frequency and drug use (e.g., by keeping a headache diary).

Pregnancy

Inform patients that AMERGE should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus.

Nursing Mothers

Advise patients to notify their healthcare provider if they are breastfeeding or plan to breastfeed.

Ability to Perform Complex Tasks

Treatment with AMERGE may cause somnolence and dizziness; instruct patients to evaluate their ability to perform complex tasks after administration of AMERGE.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Carcinogenesis

In carcinogenicity studies, mice and rats were given naratriptan by oral gavage for 104 weeks. There was no evidence of an increase in tumors related to naratriptan administration in mice receiving up to 200 mg/kg/day. That dose was associated with a plasma (AUC) exposure that was 110 times the exposure in humans receiving the MRDD of 5 mg. Two rat studies were conducted, one using a standard diet and the other a nitrite-supplemented diet (naratriptan can be nitrosated in vitro to form a mutagenic product that has been detected in the stomachs of rats fed a high-nitrite diet). Doses of 5, 20, and 90 mg/kg were associated with AUC exposures that in the standard-diet study were 7, 40, and 236 times, respectively, and in the nitrite-supplemented–diet study were 7, 29, and 180 times, respectively, the exposure in humans at the MRDD. In both studies, there was an increase in the incidence of thyroid follicular hyperplasia in high-dose males and females and in thyroid follicular adenomas in high-dose males. In the standard-diet study only, there was also an increase in the incidence of benign c-cell adenomas in the thyroid of high-dose males and females. The exposures achieved at the no-effect dose for thyroid tumors were 40 (standard diet) and 29 (nitrite-supplemented diet) times the exposure achieved in humans at the MRDD. In the nitrite-supplemented–diet study only, the incidence of benign lymphocytic thymoma was increased in all treated groups of females. It was not determined if the nitrosated product is systemically absorbed. However, no changes were seen in the stomachs of rats in that study.

Mutagenesis

Naratriptan was not mutagenic when tested in in vitro gene mutation (Ames and mouse lymphoma tk) assays. Naratriptan was also negative in the in vitro human lymphocyte assay and the in vivo mouse micronucleus assay. Naratriptan can be nitrosated in vitro to form a mutagenic product (WHO nitrosation assay) that has been detected in the stomachs of rats fed a nitrite-supplemented diet.

Impairment Of Fertility

In a reproductive toxicity study in which male and female rats were administered naratriptan orally prior to and throughout the mating period (10, 60, 170, or 340 mg/kg/day; plasma exposures [AUC] approximately 11, 70, 230, and 470 times, respectively, the human exposure at the MRDD), there was a treatment-related decrease in the number of females exhibiting normal estrous cycles at doses of 170 mg/kg/day or greater and an increase in pre-implantation loss at 60 mg/kg/day or greater. In high-dose males, testicular/epididymal atrophy accompanied by spermatozoa depletion reduced mating success and may have contributed to the observed pre-implantation loss. The exposures achieved at the no-effect doses for pre-implantation loss, anestrus, and testicular effects were approximately 11, 70, and 230 times, respectively, the exposures in humans at the MRDD.

In a study in which rats were dosed orally with naratriptan (10, 60, or 340 mg/kg/day) for 6 months, changes in the female reproductive tract including atrophic or cystic ovaries and anestrus were seen at the high dose. The exposure at the no-effect dose of 60 mg/kg was approximately 85 times that in humans at the MRDD.

Use In Specific Populations

Pregnancy

Pregnancy Category C

There are no adequate and well-controlled trials in pregnant women. AMERGE 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 naratriptan was associated with developmental toxicity (embryolethality, fetal abnormalities, pup mortality, offspring growth retardation) at doses producing maternal plasma drug exposures as low as 11 and 2.5 times, respectively, the exposure in humans receiving the maximum recommended daily dose (MRDD) of 5 mg.

When naratriptan was administered to pregnant rats during the period of organogenesis at doses of 10, 60, or 340 mg/kg/day, there was a dose-related increase in embryonic death; incidences of fetal structural variations (incomplete/irregular ossification of skull bones, sternebrae, ribs) were increased at all doses. The maternal plasma exposures (AUC) at these doses were approximately 11, 70, and 470 times the exposure in humans at the MRDD. The high dose was maternally toxic, as evidenced by decreased maternal body weight gain during gestation. A no-effect dose for developmental toxicity in rats exposed during organogenesis was not established.

When naratriptan was administered orally (1, 5, or 30 mg/kg/day) to pregnant Dutch rabbits throughout organogenesis, the incidence of a specific fetal skeletal malformation (fused sternebrae) was increased at the high dose, and increased incidences of embryonic death and fetal variations (major blood vessel variations, supernumerary ribs, incomplete skeletal ossification) were observed at all doses (4, 20, and 120 times, respectively, the MRDD on a body surface area basis). Maternal toxicity (decreased body weight gain) was evident at the high dose in this study. In a similar study in New Zealand White rabbits (1, 5, or 30 mg/kg/day throughout organogenesis), decreased fetal weights and increased incidences of fetal skeletal variations were observed at all doses (maternal exposures equivalent to 2.5, 19, and 140 times exposure in humans receiving the MRDD), while maternal body weight gain was reduced at 5 mg/kg or greater. A no-effect dose for developmental toxicity in rabbits exposed during organogenesis was not established.

When female rats were treated orally with naratriptan (10, 60, or 340 mg/kg/day) during late gestation and lactation, offspring behavioral impairment (tremors) and decreased offspring viability and growth were observed at doses of 60 mg/kg or greater, while maternal toxicity occurred only at the highest dose. Maternal exposures at the no-effect dose for developmental effects in this study were approximately 11 times the exposure in humans receiving the MRDD.

Nursing Mothers

Naratriptan is excreted in rat milk. It is not known whether naratriptan 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 AMERGE, 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.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Therefore, AMERGE is not recommended for use in patients younger than 18 years of age.

One controlled clinical trial evaluated AMERGE (0.25 to 2.5 mg) in 300 adolescent migraineurs aged 12 to 17 years who received at least 1 dose of AMERGE for an acute migraine. In this study, 54% of the patients were female and 89% were Caucasian. There were no statistically significant differences between any of the treatment groups. The headache response rates at 4 hours (n) were 65% (n = 74), 67% (n = 78), and 64% (n = 70) for placebo, 1-mg, and 2.5-mg groups, respectively. This trial did not establish the efficacy of AMERGE compared with placebo in the treatment of migraine in adolescents. Adverse reactions observed in this clinical trial were similar in nature to those reported in clinical trials in adults.

Geriatric Use

Clinical trials of AMERGE did not include sufficient numbers of patients aged 65 and older to determine whether they respond differently from younger patients. 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.

Naratriptan is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in elderly patients who have reduced renal function. In addition, elderly patients are more likely to have decreased hepatic function, they are at higher risk for CAD, and blood pressure increases may be more pronounced in the elderly.

A cardiovascular evaluation is recommended for geriatric patients who have other cardiovascular risk factors (e.g., diabetes, hypertension, smoking, obesity, strong family history of CAD) prior to receiving AMERGE.

Renal Impairment

The use of AMERGE is contraindicated in patients with severe renal impairment (creatinine clearance: < 15 mL/min) because of decreased clearance of the drug. In patients with mild to moderate renal impairment, the recommended starting dose is 1 mg, and the maximum daily dose should not exceed 2.5 mg over a 24-hour period.

Hepatic Impairment

The use of AMERGE is contraindicated in patients with severe hepatic impairment (Child-Pugh Grade C) because of decreased clearance. In patients with mild or moderate hepatic impairment (Child-Pugh Grade A or B), the recommended starting dose is 1 mg, and the maximum daily dose should not exceed 2.5 mg over a 24-hour period.

SIDE EFFECTS

The following adverse reactions are discussed in more detail in other sections of the prescribing information:

• Myocardial ischemia, myocardial infarction, and Prinzmetal's angina
• Arrhythmias
• Chest, throat, neck, and/or jaw pain/tightness/pressure
• Cerebrovascular events
• Other vasospasm reactions
• Medication overuse headache
• Serotonin syndrome
• Increase in blood pressure
• Hypersensitivity reactions

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In a long-term open-label trial where patients were allowed to treat multiple migraine attacks for up to 1 year, 15 patients (3.6%) discontinued treatment due to adverse reactions.

In controlled clinical trials, the most common adverse reactions were paresthesias, dizziness, drowsiness, malaise/fatigue, and throat/neck symptoms, which occurred at a rate of 2% and at least 2 times placebo rate.

Table 1 lists the adverse reactions that occurred in 5 placebo-controlled clinical trials of approximately 1,752 exposures to placebo and AMERGE in adult patients with migraine. Only reactions that occurred at a frequency of 2% or more in groups treated with AMERGE 2.5 mg and that occurred at a frequency greater than the placebo group in the 5 pooled trials are included in Table 1.

Table 1: Adverse Reactions Reported by at Least 2% of Patients Treated with AMERGE and at a Frequency Greater than Placebo

The incidence of adverse reactions in controlled clinical trials was not affected by age or weight of the patients, duration of headache prior to treatment, presence of aura, use of prophylactic medications, or tobacco use. There were insufficient data to assess the impact of race on the incidence of adverse reactions.

DRUG INTERACTIONS

Ergot-Containing Drugs

Ergot-containing drugs have been reported to cause prolonged vasospastic reactions. Because these effects may be additive, use of ergotamine-containing or ergot-type medications (like dihydroergotamine or methysergide) and AMERGE within 24 hours of each other is contraindicated.

Other 5-HT1 Agonists

Concomitant use of other 5-HT1B/1D agonists (including triptans) within 24 hours of treatment with AMERGE is contraindicated because the risk of vasospastic reactions may be additive.

Selective Serotonin Reuptake Inhibitors/Serotonin Norepinephrine Reuptake Inhibitors And Serotonin Syndrome

Cases of serotonin syndrome have been reported during co-administration of triptans and SSRIs, SNRIs, TCAs, and MAO inhibitors.

Pregnancy Category C

There are no adequate and well-controlled trials in pregnant women. AMERGE 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 naratriptan was associated with developmental toxicity (embryolethality, fetal abnormalities, pup mortality, offspring growth retardation) at doses producing maternal plasma drug exposures as low as 11 and 2.5 times, respectively, the exposure in humans receiving the maximum recommended daily dose (MRDD) of 5 mg.

When naratriptan was administered to pregnant rats during the period of organogenesis at doses of 10, 60, or 340 mg/kg/day, there was a dose-related increase in embryonic death; incidences of fetal structural variations (incomplete/irregular ossification of skull bones, sternebrae, ribs) were increased at all doses. The maternal plasma exposures (AUC) at these doses were approximately 11, 70, and 470 times the exposure in humans at the MRDD. The high dose was maternally toxic, as evidenced by decreased maternal body weight gain during gestation. A no-effect dose for developmental toxicity in rats exposed during organogenesis was not established.

When naratriptan was administered orally (1, 5, or 30 mg/kg/day) to pregnant Dutch rabbits throughout organogenesis, the incidence of a specific fetal skeletal malformation (fused sternebrae) was increased at the high dose, and increased incidences of embryonic death and fetal variations (major blood vessel variations, supernumerary ribs, incomplete skeletal ossification) were observed at all doses (4, 20, and 120 times, respectively, the MRDD on a body surface area basis). Maternal toxicity (decreased body weight gain) was evident at the high dose in this study. In a similar study in New Zealand White rabbits (1, 5, or 30 mg/kg/day throughout organogenesis), decreased fetal weights and increased incidences of fetal skeletal variations were observed at all doses (maternal exposures equivalent to 2.5, 19, and 140 times exposure in humans receiving the MRDD), while maternal body weight gain was reduced at 5 mg/kg or greater. A no-effect dose for developmental toxicity in rabbits exposed during organogenesis was not established.

When female rats were treated orally with naratriptan (10, 60, or 340 mg/kg/day) during late gestation and lactation, offspring behavioral impairment (tremors) and decreased offspring viability and growth were observed at doses of 60 mg/kg or greater, while maternal toxicity occurred only at the highest dose. Maternal exposures at the no-effect dose for developmental effects in this study were approximately 11 times the exposure in humans receiving the MRDD.

The following adverse reactions are discussed in more detail in other sections of the prescribing information:

• Myocardial ischemia, myocardial infarction, and Prinzmetal's angina
• Arrhythmias
• Chest, throat, neck, and/or jaw pain/tightness/pressure
• Cerebrovascular events
• Other vasospasm reactions
• Medication overuse headache
• Serotonin syndrome
• Increase in blood pressure
• Hypersensitivity reactions

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In a long-term open-label trial where patients were allowed to treat multiple migraine attacks for up to 1 year, 15 patients (3.6%) discontinued treatment due to adverse reactions.

In controlled clinical trials, the most common adverse reactions were paresthesias, dizziness, drowsiness, malaise/fatigue, and throat/neck symptoms, which occurred at a rate of 2% and at least 2 times placebo rate.

Table 1 lists the adverse reactions that occurred in 5 placebo-controlled clinical trials of approximately 1,752 exposures to placebo and AMERGE in adult patients with migraine. Only reactions that occurred at a frequency of 2% or more in groups treated with AMERGE 2.5 mg and that occurred at a frequency greater than the placebo group in the 5 pooled trials are included in Table 1.

Table 1: Adverse Reactions Reported by at Least 2% of Patients Treated with AMERGE and at a Frequency Greater than Placebo

The incidence of adverse reactions in controlled clinical trials was not affected by age or weight of the patients, duration of headache prior to treatment, presence of aura, use of prophylactic medications, or tobacco use. There were insufficient data to assess the impact of race on the incidence of adverse reactions.

Adverse reactions observed after overdoses of up to 25 mg included increases in blood pressure resulting in lightheadedness, neck tension, tiredness, and loss of coordination. Also, ischemic ECG changes likely due to coronary artery vasospasm have been reported.

The elimination half-life of naratriptan is about 6 hours , and therefore monitoring of patients after overdose with AMERGE should continue for at least 24 hours or while symptoms or signs persist. There is no specific antidote to naratriptan. It is unknown what effect hemodialysis or peritoneal dialysis has on the serum concentrations of naratriptan.

In the anesthetized dog, naratriptan has been shown to reduce the carotid arterial blood flow with little or no effect on arterial blood pressure or total peripheral resistance. While the effect on blood flow was selective for the carotid arterial bed, increases in vascular resistance of up to 30% were seen in the coronary arterial bed. Naratriptan has also been shown to inhibit trigeminal nerve activity in rat and cat.

In 10 subjects with suspected CAD undergoing coronary artery catheterization, there was a 1% to 10% reduction in coronary artery diameter following subcutaneous injection of 1.5 mg of naratriptan.

Absorption

Naratriptan is well absorbed, with about 70% oral bioavailability. Following administration of a 2.5-mg tablet, the peak concentrations are obtained in 2 to 3 hours. After administration of 1- or 2.5-mg tablets, the Cmax is somewhat (about 50%) higher in women (not corrected for milligram-per-kilogram dose) than in men. During a migraine attack, absorption is slower, with a Tmax of 3 to 4 hours. Food does not affect the pharmacokinetics of naratriptan. Naratriptan displays linear kinetics over the therapeutic dose range.

Distribution

The steady-state volume of distribution of naratriptan is 170 L. Plasma protein binding is 28% to 31% over the concentration range of 50 to 1,000 ng/mL.

Metabolism

In vitro, naratriptan is metabolized by a wide range of cytochrome P450 isoenzymes into a number of inactive metabolites.

Elimination

Naratriptan is predominantly eliminated in urine, with 50% of the dose recovered unchanged and 30% as metabolites in urine. The mean elimination half-life of naratriptan is 6 hours. The systemic clearance of naratriptan is 6.6 mL/min/kg. The renal clearance (220 mL/min) exceeds glomerular filtration rate, indicating active tubular secretion. Repeat administration of naratriptan tablets does not result in drug accumulation.