Naratriptan

The recommended dose of naratriptan tablets 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.

Naratriptan tablets are contraindicated in patients with severe renal impairment (creatinine clearance: <15 mL/min) because of decreased clearance of the drug [see Contraindications (4), Use in Specific Populations (8.6), Clinical Pharmacology (12.3)].

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 [see Use in Specific Populations (8.6), Clinical Pharmacology (12.3)].

Naratriptan tablets are contraindicated in patients with severe hepatic impairment (Child-Pugh Grade C) because of decreased clearance [see Contraindications (4), Use in Specific Populations (8.7), Clinical Pharmacology (12.3)].

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 [see Use in Specific Populations (8.7), Clinical Pharmacology (12.3)].

Naratriptan tablets are 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 naratriptan tablets. Some of these reactions occurred in patients without known CAD. Naratriptan tablets 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 naratriptan tablets. If there is evidence of CAD or coronary artery vasospasm, naratriptan tablets are contraindicated. For patients with multiple cardiovascular risk factors who have a negative cardiovascular evaluation, consider administering the first dose of naratriptan tablets in a medically supervised setting and performing an electrocardiogram (ECG) immediately following administration of naratriptan tablets. For such patients, consider periodic cardiovascular evaluation in intermittent long-term users of naratriptan tablets.

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 naratriptan tablets if these disturbances occur. Naratriptan tablets are contraindicated in patients with Wolff-Parkinson-White syndrome or arrhythmias associated with other cardiac accessory conduction pathway disorders.

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

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 naratriptan tablets 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. Naratriptan tablets are contraindicated in patients with a history of stroke or TIA.

Naratriptan tablets 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 naratriptan tablets.

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.

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 may occur with naratriptan tablets, particularly during co-administration with selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), and monoamine oxidase (MAO) inhibitors [see Drug Interactions (7.3)]. 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 naratriptan tablets if serotonin syndrome is suspected.

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 naratriptan tablets. Naratriptan tablets are contraindicated in patients with uncontrolled hypertension.

There have been reports of anaphylaxis and hypersensitivity reactions, including angioedema, in patients receiving naratriptan tablets. 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. Naratriptan tablets are contraindicated in patients with a history of hypersensitivity reaction to naratriptan tablets.

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 naratriptan tablets in adult patients with migraine. Only reactions that occurred at a frequency of 2% or more in groups treated with naratriptan tablets 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 Naratriptan Tablets 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.

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 naratriptan tablets within 24 hours of each other is contraindicated.

Concomitant use of other 5-HT_1B/1D agonists (including triptans) within 24 hours of treatment with naratriptan tablets is contraindicated because the risk of vasospastic reactions may be additive.

Cases of serotonin syndrome have been reported during co-administration of triptans and SSRIs, SNRIs, TCAs, and MAO inhibitors [see Warnings and Precautions (5.7)].

Teratogenic Effects:

Risk Summary
There are no adequate data on the developmental risk associated with use of naratriptan tablets in pregnant women. Data from a prospective pregnancy exposure registry and epidemiological studies of pregnant women have documented outcomes in women exposed to naratriptan during pregnancy; however, due to small sample sizes, no definitive conclusions can be drawn regarding the risk of birth defects following exposure to naratriptan [see Data]. In animal studies, naratriptan produced developmental toxicity (including embryolethality and fetal abnormalities) when administered to pregnant rats and rabbits. The lowest doses producing evidence of developmental toxicity in animals were associated with plasma exposures 2.5 (rabbit) to 11 (rat) times that in humans at the maximum recommended daily dose (MRDD) [see Data].

In the U.S. general population, the estimated background risk of major birth defects and of miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The reported rate of major birth defects among deliveries to women with migraine ranged from 2.2% to 2.9% and of miscarriage was 17%, which were similar to rates reported in women without migraine.

Clinical Considerations
Disease-Associated Maternal and/or Embryo/Fetal Risk
Several studies have suggested that women with migraine may be at increased risk of preeclampsia during pregnancy.

Data
Human Data: The numbers of exposed pregnancy outcomes accumulated during the Sumatriptan/Naratriptan/Treximet^®(sumatriptan and naproxen sodium) Pregnancy Registry, a population-based international prospective study that collected data from October 1997 to September 2012, and smaller observational studies, were insufficient to define a level of risk for naratriptan in pregnant women. The Registry documented outcomes of 57 infants and fetuses exposed to naratriptan during pregnancy (52 exposed during the first trimester and 5 exposed during the second trimester). The occurrence of major birth defects (excluding fetal deaths and induced abortions without reported defects and all spontaneous pregnancy losses) during first-trimester exposure to naratriptan was 2.2% (1/46 [95% CI: 0.1% to 13%]) and during any trimester of exposure was 2% (1/51 [95% CI: 0.1% to 11.8%]). Seven infants were exposed to both naratriptan and sumatriptan in utero, and one of these infants with first-trimester exposure was born with a major birth defect (ventricular septal defect). The sample size in this study had 80% power to detect at least a 3.8 to 4.6 fold increase in the rate of major malformations.

In a study using data from the Swedish Medical Birth Register, women who used triptans or ergots during pregnancy were compared with women who did not. Of the 22 births with first-trimester exposure to naratriptan, one infant was born with a malformation (congenital deformity of the hand).

Animal Data: 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, the incidence of fetal variations (major blood vessel variations, supernumerary ribs, incomplete skeletal ossification) was increased at the mid and high doses, and embryonic death was increased 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 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.

Risk Summary
There are no data on the presence of naratriptan in human milk, the effects of naratriptan on the breastfed infant, or the effects of naratriptan on milk production. Naratriptan is present in rat milk.

The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for naratriptan tablets and any potential adverse effects on the breastfed infant from naratriptan or from the underlying maternal condition.

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

One controlled clinical trial evaluated naratriptan tablets (0.25 to 2.5 mg) in 300 adolescent migraineurs aged 12 to 17 years who received at least 1 dose of naratriptan tablets 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 naratriptan tablets 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.

Clinical trials of naratriptan tablets 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 naratriptan tablets [see Warnings and Precautions (5.1)].

The use of naratriptan tablets 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 [see Dosage and Administration (2.2), Clinical Pharmacology (12.3)].

The use of naratriptan tablets 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 [see Dosage and Administration (2.3), Clinical Pharmacology (12.3)].

Naratriptan binds with high affinity to human cloned 5-HT_1B/1D receptors. Migraines are likely due to local cranial vasodilatation and/or to the release of sensory neuropeptides (including substance P and calcitonin gene-related peptide) through nerve endings in the trigeminal system. The therapeutic activity of naratriptan tablets 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.

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 [see Contraindications (4)].

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 C_max 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 T_max 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.

Special Populations

Age: A small decrease in clearance (approximately 26%) was observed in healthy elderly subjects (65 to 77 years) compared with younger subjects, resulting in slightly higher exposure [see Use in Specific Populations (8.5)].

Race: The effect of race on the pharmacokinetics of naratriptan has not been examined.

Renal Impairment: Clearance of naratriptan was reduced by 50% in subjects with moderate renal impairment (creatinine clearance: 18 to 39 mL/min) compared with the normal group. Decrease in clearances resulted in an increase of mean half-life from 6 hours (healthy) to 11 hours (range: 7 to 20 hours). The mean C_max increased by approximately 40%. The effects of severe renal impairment (creatinine clearance:≤15 mL/min) on the pharmacokinetics of naratriptan have not been assessed [see Contraindications (4)].

Hepatic Impairment: Clearance of naratriptan was decreased by 30% in subjects with moderate hepatic impairment (Child-Pugh grade A or B). This resulted in an approximately 40% increase in the half-life (range: 8 to 16 hours). The effects of severe hepatic impairment (Child-Pugh grade C) on the pharmacokinetics of naratriptan have not been assessed [see Contraindications (4)].

Drug Interaction Studies

From population pharmacokinetic analyses, co-administration of naratriptan and fluoxetine, beta-blockers, or tricyclic antidepressants did not affect the clearance of naratriptan.

Oral Contraceptives: Oral contraceptives reduced clearance by 32% and volume of distribution by 22%, resulting in slightly higher concentrations of naratriptan. Hormone replacement therapy had no effect on pharmacokinetics in older female patients.

Monoamine Oxidase and P450 Inhibitors: Naratriptan does not inhibit monoamine oxidase (MAO) enzymes and is a poor inhibitor of P450; metabolic interactions between naratriptan and drugs metabolized by P450 or MAO are therefore unlikely.

Smoking: Smoking increased the clearance of naratriptan by 30%.

Alcohol: In normal volunteers, co-administration of single doses of naratriptan tablets and alcohol did not result in substantial modification of naratriptan pharmacokinetic parameters.

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 drug-related decrease in the number of females exhibiting normal estrous cycles at doses of 170 mg/kg/day or greater and an increase in preimplantation 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 preimplantation loss. The exposures achieved at the no-effect doses for preimplantation 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.