Rizatriptan Benzoate

Description

Rizatriptan Benzoate is a selective 5-hydroxytryptamine (5-HT1) receptor agonist.

Mechanism of Action

Rizatriptan binds with high affinity to human cloned 5-HT1B and 5-HT1D receptors. Activation of these receptors results in cranial vessel constriction, inhibition of neuropeptide release and reduced transmission in trigeminal pain pathways.

Pharmacokinetics

Rizatriptan is completely absorbed following oral administration. The mean oral absolute bioavailability is about 45 per cent and mean peak plasma concentrations (Cmax ) are reached in approximately 1-1.5 hours (Tmax). Food has no significant effect on the bioavailability of rizatriptan but delays the time to reach peak concentration by an hour. The plasma half-life of rizatriptan in males and females averages 2-3 hours. No accumulation occurred on multiple dosing.

Rizatriptan is metabolised, primarily by monoamine oxidase type A to the inactive indole acetic acid derivative. The active metabolite N-monodesmethyl-rizatriptan is formed to a minor degree; other minor metabolites are also produced. About 14 per cent of an oral dose is excreted in the urine as unchanged rizatriptan, 51 per cent as the indole acetic acid metabolite and 1 per cent as N-monodesmethyl-rizatriptan. The plasma half-life is about 2 to 3 hours.

Composition

Each film-coated tablet contains Rizatriptan Benzoate INN equivalent to 5 mg of Rizatriptan.

Indications

Rizatriptan Benzoate is indicated for the acute treatment of migraine attacks in adults. But it is not intended for the prophylactic therapy of migraine.

Dosage and Administration

Single doses of 5 mg or 10 mg tablets are effective for acute treatment of migraine in adults.

More than 30 mg of Rizatriptan should not be taken in any 24 hour period. Dosage interval should be at least 2 hours.

In patients receiving propranolol, the 5 mg dose of RIZAT should be used, up to a maximum of 3 doses in any 24 hour period.

Contraindications

Rizatriptan is contraindicated in patients who are hypersensitive to Rizatriptan or any of its ingredients.

Rizatriptan should not be given to patients with ischemic heart disease (e.g. angina pectoris, history of myocardial infarction or documented silent ischemia) or to patients who have symptoms or findings consistent with ischemic heart disease, coronary artery vasospasm, including prinzmetal's variant angina or other significant underlying cardiovascular diseases.

It should not be used within 24 hours of treatment with another 5-HT1 agonist or an ergotamine containing or ergot-type medications like dihydroergotamine or methysergide.

Rizatriptan should not be administered to patients with hemiplegic or basilar migraine. Concurrent administration of MAO inhibitors or use of Rizatriptan within 2 weeks of discontinuation of MAO inhibitor therapy is also contraindicated.

Because Rizatriptan may increase blood pressure, it should not be given to patients with uncontrolled hypertension.

Side Effects

Side effects of Rizatriptan that may occur while taking this medicine include dizziness, drowsiness, nausea, fatigue, palpitation, tachycardia, dry mouth, diarrhoea, dyspepsia, thirst, pharyngeal discomfort, dyspnea, headache, decreased alertness, insomnia, tremor, ataxia, nervousness, vertigo, myalgia and muscle weakness, sweating, urticaria, pruritus, blurred vision, hypertension, hypersensitivity reactions (including rash, angioedema and toxic epidermal necrolysis) and taste disturbance.

Use in Pregnancy and Lactation

There are no adequate and well-controlled studies in pregnant women. Rizatriptan crosses the placenta in animals. Thus Rizatriptan should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus (Pregnancy category C).

It is not known whether this drug is excreted in human milk. So, caution should be exercised when Rizatriptan is administered to women who are breast feeding.

Use in Children and Elderly

Safety and effectiveness of Rizatriptan in pediatric patients have not been established; therefore, it is not recommended in children and adolescents under 18 years.

Rizatriptan does not cause different side effects in older people (over 65 years) than it does in younger adults. There are no apparent differences in efficacy of it between adults and elderly.

Precautions

Rizatriptan should be used with caution in conditions that predispose to coronary artery disease, and hepatic impairment. In case of renal impairment it should not be taken until 24 hours after stopping an ergotamine type preparation. Rizatriptan is recommended as monotherapy and should not be taken concurrently with other acute migraine therapies.

Drug Interactions

Propranolol:

Concurrent administration of propranolol and Rizatriptan increases mean plasma AUC for Rizatriptan. The AUC of the active N-monodesmethyl metabolite of Rizatriptan is not affected by propranolol.

Nadolol/Metoprolol:

No pharmacokinetic interactions are observed.

Paroxetine:

Neither the plasma concentrations of Rizatriptan nor its safety profile is affected by paroxetine when concurrently used with Rizatriptan.

Oral Contraceptive:

Concurrent administration of Rizatriptan with an oral contraceptive does not affect plasma concentrations of ethinyl estradiol or norethindrone.

Overdosage

Hypertension or other more serious cardiovascular symptoms could occur after overdose of Rizatriptan. Symptoms of overdose may include unusual dizziness or drowsiness, slow, fast or irregular heartbeat and vomiting.

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