Imitrex 50 mg Tablets

Brand Name

The medication is marketed under the brand name Imitrex, a widely recognized label in the field of neurological and pain management therapies.

International Nonproprietary Name (INN)

The active ingredient in this product is identified globally as sumatriptan, a name standardized for consistency across international pharmacological practices.

Form of Release

Imitrex is available in multiple forms, including oral tablets, nasal spray, and subcutaneous injection. Tablets come in strengths of 25 mg, 50 mg, and 100 mg, while the nasal spray is offered in 5 mg and 20 mg doses per spray, and the injection provides 4 mg or 6 mg per 0.5 mL dose, typically in prefilled syringes or autoinjectors.

Composition

Each tablet of Imitrex contains sumatriptan succinate as the primary active substance, with dosages varying by strength (25 mg, 50 mg, or 100 mg, equivalent to sumatriptan base). The formulation includes several inactive ingredients, such as microcrystalline cellulose, which provides structural support, and lactose monohydrate, acting as a filler. Additional excipients like croscarmellose sodium facilitate disintegration, while magnesium stearate serves as a lubricant. The nasal spray includes sodium phosphate and sulfuric acid for pH adjustment, and the injection contains sodium chloride for isotonicity. These components ensure effective delivery across all administration routes.

Pharmacologic Properties

Pharmacodynamics

Imitrex functions as a selective serotonin (5-HT1B/1D) receptor agonist, targeting receptors in cranial blood vessels and sensory nerves of the trigeminal system. It relieves migraine symptoms by constricting dilated extracerebral blood vessels, a key feature of migraine pathophysiology, and inhibiting the release of pro-inflammatory neuropeptides like calcitonin gene-related peptide (CGRP). This dual action reduces vascular inflammation and blocks pain signal transmission in the brainstem, effectively aborting migraine attacks with or without aura.

The medication does not prevent migraines but acts acutely to halt progression once symptoms begin. Clinical studies show it alleviates headache, nausea, photophobia, and phonophobia in 50–70% of patients within 2 hours of oral dosing, with faster onset via injection. Its specificity for 5-HT1 receptors minimizes effects on other serotonin subtypes, reducing systemic side effects compared to non-selective agents. This targeted mechanism underpins its efficacy in acute migraine management.

Pharmacokinetics

Following oral administration, Imitrex is absorbed from the gastrointestinal tract, with peak plasma concentrations reached within 1 to 2 hours. Bioavailability is approximately 15% due to extensive first-pass metabolism, and food slightly delays absorption without altering extent. The nasal spray achieves peak levels in 0.5 to 1.5 hours with 10–20% bioavailability, while subcutaneous injection peaks within 10–15 minutes, offering nearly 97% bioavailability.

Distribution includes moderate plasma protein binding (14–21%), allowing penetration into peripheral tissues, though it crosses the blood-brain barrier minimally. Metabolism occurs primarily in the liver via monoamine oxidase (MAO)-A, converting sumatriptan into an inactive indole acetic acid metabolite. The half-life is about 2 hours across all forms, with elimination predominantly renal—60% of the oral dose appears in urine as metabolites, and 40% unchanged via feces—supporting short-term action and repeat dosing if needed.

Indications for Use

Imitrex is prescribed for the acute treatment of migraine attacks with or without aura in adults. It addresses the headache phase and associated symptoms like nausea, vomiting, and sensitivity to light or sound, offering rapid relief when taken at onset. The injection form is also indicated for cluster headaches, a severe condition marked by unilateral pain and autonomic symptoms, providing swift resolution in this context.

It is not intended for migraine prophylaxis or management of hemiplegic or basilar migraines, which involve distinct neurological risks. The medication suits patients with moderate to severe attacks unresponsive to over-the-counter analgesics, restoring function during acute episodes. Its multi-form availability enhances accessibility for diverse patient needs and preferences in managing these debilitating conditions.

Contraindications

Imitrex is contraindicated in patients with ischemic heart disease, such as angina, myocardial infarction, or silent ischemia, due to its vasoconstrictive effects, which could precipitate cardiac events. It is also prohibited in those with a history of stroke, transient ischemic attack, or peripheral vascular disease, where vascular risks are heightened.

Uncontrolled hypertension, severe liver impairment, or hypersensitivity to sumatriptan or any formulation component (e.g., lactose in tablets) preclude its use. Co-administration with monoamine oxidase inhibitors (MAOIs) or within 2 weeks of discontinuation is forbidden due to metabolic interference. Patients with Wolff-Parkinson-White syndrome or other cardiac accessory conduction pathway disorders should avoid it, as should those with a history of serotonin syndrome when combined with similar agents.

Method of Administration and Dosage

Administration Guidelines

Oral tablets should be taken with water, with or without food, at the first sign of a migraine. The nasal spray is administered as a single spray into one nostril, avoiding inhalation or multiple sprays unless directed. Subcutaneous injection is delivered into the thigh or upper arm using a prefilled device, ensuring rapid onset. Patients should not mix forms in a single attack unless advised by a healthcare provider.

Dosage for Adults and Children

For adults with migraines, the oral dose of Imitrex is 25 mg, 50 mg, or 100 mg, with 50 mg as the usual starting point, repeatable after 2 hours if needed, up to 200 mg daily. The nasal spray uses 5 mg, 10 mg, or 20 mg per attack, with a maximum of 40 mg daily, while the injection starts at 6 mg, repeatable once after 1 hour, up to 12 mg daily. Cluster headaches use 6 mg injections, with the same daily limit. Children under 18 are not typically prescribed this therapy, as safety and efficacy remain unestablished in pediatric populations.

Dose Adjustment in Specific Conditions

In mild to moderate liver impairment, oral doses should not exceed 50 mg per attack due to reduced clearance, while severe impairment contraindicates use. Renal dysfunction does not require adjustment, as kidney excretion is secondary. Elderly patients or those with cardiovascular risk factors may need lower starting doses and close monitoring. Repeat dosing should align with symptom recurrence, not exceed daily limits, and be guided by response and tolerance.

Side Effects

Imitrex may cause various side effects, though many patients experience only mild or short-lived reactions. Common issues include tingling, warmth, or pressure sensations, particularly with injections, reflecting its vascular effects. Dizziness, fatigue, or nausea are also reported, often resolving within hours post-dose.

Less frequent effects include chest tightness, neck pain, or muscle stiffness, which may mimic cardiac symptoms but are typically benign. Rare but serious reactions, such as coronary vasospasm, arrhythmias, or serotonin syndrome (with serotonergic drugs), require immediate cessation and medical attention. Injection site reactions or nasal irritation may occur with non-oral forms. Monitoring during initial use helps distinguish transient effects from concerning symptoms.

Overdose

Symptoms of Overdose

Excessive intake of Imitrex may amplify typical side effects, including severe dizziness, tremors, or chest pressure, with rare reports of seizures or hypertension. Doses exceeding 200 mg orally or 12 mg injected have shown no consistent acute toxicity pattern, but symptoms reflect exaggerated vasoconstriction and serotonin activity.

First Aid Measures

In case of overdose, medical consultation is advised, with monitoring for cardiovascular or neurological changes. No specific antidote exists, so treatment focuses on supportive care, such as hydration or rest, and symptomatic relief (e.g., antihypertensives if needed). Dialysis is ineffective due to rapid metabolism, and observation continues until symptoms subside, typically within hours.

Drug Interactions

Effects on Other Medications

Imitrex is metabolized by MAO-A, so co-use with MAOIs increases sumatriptan levels, risking toxicity, and is contraindicated. Combining with other serotonergic drugs, like SSRIs or SNRIs, may precipitate serotonin syndrome, marked by agitation or hyperthermia, requiring careful monitoring. Ergotamines or other triptans within 24 hours heighten vasoconstriction risk, necessitating spacing.

It does not significantly affect cytochrome P450 enzymes, minimizing interactions with drugs like warfarin or theophylline. Patients should report all medications to their healthcare provider to avoid additive effects, particularly in polypharmacy settings.

Compatibility with Alcohol and Food

Moderate alcohol use does not directly alter the drug’s efficacy, though it may exacerbate migraine triggers or side effects like dizziness. Food delays oral absorption slightly but does not reduce overall effect, allowing flexibility in timing, though injections and sprays are unaffected.

Special Precautions

Use During Pregnancy and Breastfeeding

Imitrex is Category C in pregnancy, with animal studies suggesting potential fetal risks but limited human data. Use is reserved for cases where benefits outweigh risks, guided by medical advice. It passes into breast milk in small amounts, so breastfeeding should be paused for 12 hours post-dose to minimize infant exposure, with alternatives considered if frequent use is needed.

Women of childbearing age should confirm non-pregnant status before use and consider contraception during therapy to avoid unintended fetal exposure.

Impact on Driving and Operating Machinery

The medication may cause dizziness or drowsiness in some patients, suggesting caution with driving or machinery until tolerance is clear. Most individuals resume normal activities post-dose once migraine resolves, but initial use warrants observation for sedative effects.

Considerations for Elderly and Pediatric Populations

Elderly patients tolerate Imitrex well, though cardiovascular risk assessment is critical, and lower doses may be preferred. Children under 18 are not typically prescribed this therapy, as safety and efficacy remain untested, limiting its use to adults unless exceptional circumstances apply.