Migatex

Migatex Tablets are indicated for the acute treatment of migraine attacks with or without aura.

Migatex tablets should be taken as early as possible after the onset of a migraine headache but they are effective if taken at a later stage.

Migatex Tablets are recommended as monotherapy for the acute treatment of a migraine attack.

Migatex Tablets should not be used prophylactically.

Posology

Adults (18-65 years of age)

The recommended dose of Migatex Tablets is a single 2.5mg tablet.

The total dose should not exceed two 2.5mg tablets in any 24 hour period.

If symptoms of migraine should recur, following an initial response, a second dose may be taken provided that there is a minimum interval of four hours between the two doses.

If a patient does not respond to a first dose of Migatex Tablets a second dose should not be taken for the same attack, as it is unlikely to be of benefit. However Migatex Tablets may be used for subsequent migraine attacks.

Adolescents (12-17 years of age)

Efficacy of Migatex Tablets at single doses of 0.25, 1.0 and 2.5mg was not demonstrated to be greater than placebo in a placebo-controlled study in adolescents (12 to 17 years). Therefore, the use of Migatex Tablets in patients under 18 years of age is not recommended.

Children (under 12 years of age)

There are no data available on the use of naratriptan in children under 12 years of age therefore its use in this age group is not recommended.

Elderly (over 65 years of age)

The safety and effectiveness of naratriptan in individuals over age 65 have not been evaluated and therefore, its use in this age group can not be recommended. There is a moderate decrease in clearance with age (see Pharmacokinetics).

Renal Impairment

Migatex should be used with caution in patients with renal impairment. The maximum dose in any 24 hour treatment period is a single 2.5mg tablet. The use of Migatex is contraindicated in patients with severe renal impairment (creatinine clearance < 15mL/min)

(See Contraindications and Pharmacokinetics).

Hepatic Impairment

Migatex should be used with caution in patients with hepatic impairment. The maximum dose in any 24 hour treatment period is a single 2.5mg tablet. The use of Migatex is contraindicated in patients with severe hepatic impairment (Child-Pugh grade C)

(See Contraindications and Pharmacokinetics).

Method of administration

Migatex Tablets should be swallowed whole with water.

As with other 5-hydroxytryptamine1 (5-HT1) receptor agonists naratriptan should not be used in patients who have had a myocardial infarction or have ischaemic heart disease, or Prinzmetal's angina/coronary vasospasm, peripheral vascular disease or patients who have symptoms or signs consistent with ischaemic heart disease.

Naratriptan should not be administered to patients with a history of cerebrovascular accident (CVA) or transient ischaemic attack (TIA).

The use of naratriptan in patients with moderate or severe hypertension, and mild uncontrolled hypertension is contraindicated.

The concomitant administration of ergotamine, derivatives or ergotamine (including methysergide) or/and any triptan/5-hydroxytryptamine₁ (5-HT₁) receptor agonist with naratriptan is contraindicated.

Naratriptan is contraindicated in patients with severely impaired renal (creatinine clearance <15 ml/min) or hepatic function (Child-Pugh grade C).

Naratriptan should only be used where there is a clear diagnosis of migraine.

Naratriptan is not indicated for use in the management of hemiplegic, basilar or ophthalmoplegic migraine.

As with other acute migraine therapies, before treating headaches in patients not previously diagnosed as migraineurs, and in migraineurs who present with atypical symptoms, care should be taken to exclude other potentially serious neurological conditions. It should be noted that migraineurs may be at risk of certain cerebrovascular events (eg. CVA or TIA).

The safety and efficacy of naratriptan when administered during the aura phase, prior to the onset of migraine headache, has yet to be established.

As with other 5-HT1 receptor agonists, naratriptan should not be given to patients with risk factors for ischaemic heart disease, including those patients who are heavy smokers or users of nicotine substitution therapy without prior cardiovascular evaluation. Special consideration should be given to postmenopausal women and males over 40 with these risk factors. These evaluations however, may not identify every patient who has cardiac disease and, in very rare cases, serious cardiac events have occurred in patients without underlying cardiovascular disease when 5-HT1 agonists have been administered.

Following administration, naratriptan can be associated with transient symptoms including chest pain and tightness which may be intense and involve the throat. Where such symptoms are thought to indicate ischaemic heart disease, no further doses of naratriptan should be taken and appropriate evaluation should be carried out.

Serotonin syndrome (including altered mental status, autonomic instability and neuromuscular abnormalities) has been reported following concomitant treatment with triptans and selective serotonin reuptake inhibitors (SSRIs)/serotonin noradrenaline reuptake inhibitors (SNRIs). If concomitant treatment with naratriptan and an SSRI/SNRI is clinically warranted, appropriate observation of the patient is advised, particularly during treatment initiation, with dose increases, or with addition of another serotonergic medication.

Naratriptan contains a sulphonamide component therefore there is a theoretical risk of a hypersensitivity reaction in patients with known hypersensitivity to sulphonamides.

The recommended dose of naratriptan should not be exceeded.

Prolonged use of any type of painkiller for headaches can make them worse. If this situation is experienced or suspected, medical advice should be obtained and treatment should be discontinued. The diagnosis of MOH should be suspected in patients who have frequent or daily headaches despite (or because of) the regular use of headache medications.

Undesirable effects may be more common during concomitant use of triptans and herbal preparations containing St John's Wort (Hypericum perforatum).

This medicinal product contains anhydrous lactose, patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Drowsiness may occur as a result of migraine or its treatment with naratriptan. Caution is recommended when skilled tasks are to be performed (e.g. driving or operating machinery).

At therapeutic doses of naratriptan the incidence of side effects reported in clinical trials was similar to placebo. Some of the symptoms may be part of the migraine attack.

Undesirable effects are ranked under headings of frequency using the following convention: Very common (>1/10), common (>1/100 and <1/10), uncommon (>1/1,000 and <1/100), rare (>1/10,000 and <1/1,000) and very rare (<1/10,000).

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.

Administration of a high dose of 25 mg naratriptan in one healthy male subject increased blood pressure by up to 71 mmHg and resulted in adverse events including light-headedness, tension in the neck, tiredness and a loss of co-ordination. Blood pressure returned to baseline by 8 hours after dosing without other pharmacological intervention.

It is unknown what effect haemodialysis or peritoneal dialysis has on the plasma concentrations of naratriptan.

Treatment

If overdosage with naratriptan occurs, the patient should be monitored for at least 24 hours and standard supportive treatment applied as required.

Mechanism of action

Naratriptan has been shown to be a selective agonist for 5 hydroxytryptamine1 (5-HT₁) receptors mediating vascular contraction. This receptor is found predominantly in intracranial (cerebral and dural) blood vessels. Naratriptan has high affinity for human cloned 5-HT_1B and 5-HT_1D receptors, the human 5-HT_1B receptor is thought to correspond to the vascular 5-HT₁ receptor mediating contraction of intracranial blood vessels. Naratriptan has little or no effect at other 5-HT receptor (5-HT₂, 5-HT₃, 5-HT₄ and 5-HT₇) subtypes.

Pharmacodynamic effect

In animals, naratriptan selectively constricts the carotid arterial circulation. This circulation supplies blood to the extracranial and intracranial tissues such as the meninges, and dilatation and/or oedema formation in these vessels is thought to be the underlying mechanism of migraine in man. In addition, experimental evidence suggests that naratriptan inhibits trigeminal nerve activity. Both these actions may contribute to the anti-migraine action of naratriptan in humans.

Clinical efficacy and safety

In man, a meta-analysis of BP recordings in 15 studies showed that the population average maximum increases in systolic and diastolic blood pressure after a 2.5mg dose of naratriptan tablets would be less than 5mmHg and 3mmHg respectively. The blood pressure response was unaffected by age, weight, hepatic or renal impairment.

Absorption

Following oral administration, naratriptan is rapidly absorbed with maximum plasma concentrations observed at 2-3 hours. After administration of a 2.5mg naratriptan tablet Cmax is approximately 8.3ng/mL (95% Cl: 6.5 to 10.5ng/mL) in women and 5.4ng/mL (95% Cl: 4.7 to 6.1ng/mL) in men.

The oral bioavailability is 74% in women and 63% in men with no differences in efficacy and tolerability in clinical use. Therefore a gender related dose adjustment is not required.

Distribution

Naratriptan is distributed in a volume of 170L. Plasma protein binding is low (29%).

Biotransformation

Mean clearance after intravenous administration was 470mL/min in men and 380mL/min in women. Renal clearance is similar in men and women at 220mL/min and is higher than the glomerular filtration rate suggesting that naratriptan is actively secreted in the renal tubules. Naratriptan is predominantly excreted in the urine with 50% of the dose recovered as unchanged naratriptan and 30% recovered as inactive metabolites. In vitro naratriptan was metabolised by a wide range of cytochrome P450 isoenzymes. Consequently significant metabolic drug interactions with naratriptan are not anticipated.

Elimination

The mean elimination half-life (t_1/2) is 6 hours.

Special Patient Populations

Elderly

In healthy elderly subjects (n=12), clearance was decreased by 26% when compared to healthy young subjects (n=12) in the same study (See Posology and method of administration).

Gender

The naratriptan AUC and Cmax were approximately 35% lower in males compared to females however, with no differences in efficacy and tolerability in clinical use.

Therefore a gender related dose adjustment is not required (see Posology and method of administration).

Renal impairment

Renal excretion is the major route for the elimination of naratriptan. Accordingly exposure to naratriptan may be increased in patients with renal disease.

In a study in male and female renally impaired patients (creatinine clearance 18 to 115mL/min; n=15) matched for sex, age and weight with healthy subjects (n=8), renally impaired patients had an approximately 80% increase in t_1/2 and an approximately 50% reduction in clearance (See Posology and method of administration).

Hepatic impairment

The liver plays a lesser role in the clearance of orally administered naratriptan. In a study in male and female hepatically impaired patients (Child-Pugh grade A or B n=8) matched for sex, age and weight with healthy subjects who received oral naratriptan, hepatically impaired patients had an approximately 40% increase in t_1/2 and an approximately 30% reduction in clearance (See Posology and method of administration).

No clinically relevant findings were observed in preclinical studies.

None reported

No special requirements for disposal.