Imitrex Explained: Usage, Dosage, And Side Effects

Imitrex is a brand-name prescription medication (generic name: sumatriptan) used to treat migraine attacks, per WebMD. It is highly effective in helping to alleviate a variety of migraine symptom including throbbing headache, pain, nausea, and vomiting. Imitrex also relieves photophobia — sensitivity to light — which occurs in up to 90% of people living with migraines (via Medical News Today). 

According to Sumatriptan, Imitrex works by causing vasoconstriction (narrowing) of blood vessels in the brain and by blocking transmission of pain signals to the brain. Imitrex is FDA approved for the treatment of migraines in adults, but not in children and adolescents. Imitrex can be taken by mouth, as a nasal spray, or via injection. The injectable version is also approved to treat cluster headaches. Cluster headaches are severe headaches lasting 30-45 minutes and occurring in groups, up to eight per day, and persisting for weeks to several months before remission (via the Cleveland Clinic). 

The most common side effects of Imitrex are mild and resolve over time. These include dizziness, fatigue, and tingling in the fingers or toes. Serious symptoms requiring emergency assistance (e.g., heart attack, stroke, or shortness of breath) can also occur. New research suggests that Imitrex, apart from being a migraine medicine, may potentially be used in the treatment of inflammatory conditions such as nerve inflammation resulting from spinal cord injury (via a 2020 study in Neurological Research). 

How does Imitrex work for migraine headaches?

Imitrex belongs to a class of drugs known as triptans (hence the generic name sumatriptan), explains a 2014 summary of four reviews published in the Cochrane Data Base of Systematic Reviews. By binding to receptors for the brain neurotransmitter serotonin, Imitrex and other triptans mimic the actions of the serotonin in the brain. For example, Imitrex — like serotonin — causes narrowing of excessively dilated blood vessels in the brain. This relieves the migraine pain caused by distended blood vessels pushing up against nerve cells (per Office on Women's Health). Imitrex also works by blocking the release from overactive nerve cells of peptides that cause inflammation and pain (via Sumatriptan). In a third mechanism of action, Imitrex disrupts the transmission of pain signals within the trigeminal nerve in the brain. The trigeminal nerve transmits pain sensation from the face to the brain (via the Cleveland Clinic).

Using Imitrex with other drugs

In some cases of migraines treated with Imitrex, other drugs may be recommended as well, per Healthline. Over-the-counter (OTC) medicines for pain relief include Tylenol (acetaminophen), Excedrin (acetaminophen, aspirin, and caffeine), and NSAIDs such as Aleve (naproxen) and Advil (ibuprofen). For severe pain issues, stronger prescription medications such as Ultram (tramadol) may be necessary. Among other prescription painkillers are diclofenac, Fioricet (butalbital, acetaminophen, and caffeine), Fiorinal (butalbital, aspirin, and caffeine), and Tylenol with codeine (via Medical News Today). Zofran, Phenergan, and other drugs may be prescribed in cases of nausea. Caution is advised if pain relievers are used for 10 days or more per month, since overuse could backfire and cause headaches. 

Since Imitrex is used exclusively for the treatment of migraines and cluster headaches, other drugs may be recommended for their prevention, continues Medical News Today. Topamax (topiramate), Inderal (propranolol), and Neurontin (gabapentin) are some common prescription drugs used for migraine prevention. Other preventative medicines include Depakote (divalproex sodium), Calan (verapamil), Aimovig (erenumab), and Ajovy (fremanezumab-vfrm). 

Contraindications for using Imitrex

According to Sumatriptan, Imitrex should not be used in people with severe liver disease. It is also contraindicated in various circulatory disorders such as peripheral arterial disease, cerebrovascular syndrome, or high blood pressure that is not controlled. People with ischemic heart disease can use Imitrex, but with caution. Some examples of ischemic heart disease are heart attack, coronary artery vasospasm, and angina pectoris (chest pain). 

Per WebMD, Imitrex cannot be taken by people on antidepressant medications known as MAO (monoamine oxidase) inhibitors, including isocarboxazid, phenelzine, selegiline, and tranylcypromine. Also, MAO inhibitors should be discontinued for two weeks before starting Imitrex. Other types of antidepressant medications that are contraindicated with Imitrex are the SSRIs (selective serotonin reuptake inhibitors) Prozac (fluoxetine) and Paxil (paroxetine) as well as the street drug ecstasy and the herb St. John's wort. Since both MAO inhibitors and SSRIs increase serotonin, taking these drugs with Imitrex (which mimics serotonin) can lead to serotonin syndrome. 

Serotonin syndrome

Serotonin syndrome is a potentially fatal condition that develops as a result of high levels of serotonin in the body (via the Mayo Clinic). Imitrex mimics serotonin by acting on the same receptors in the body, and thus exerting similar effects. Imitrex taken together with antidepressants and other drugs can cause serotonin to accumulate, resulting in serotonin syndrome. In addition to SSRIs and MAO inhibitors, other antidepressants that increase serotonin include SNRIs (serotonin and norepinephrine reuptake inhibitors) such as Pristiq, Cymbalta, and Effexor. The tricyclic antidepressants (e.g., amitriptyline and nortriptyline) as well as Wellbutrin and Zyban also affect serotonin. Some pain medications, anti-nausea drugs, lithium, the antibiotic Zyvox, and the HIV drug Norvir can impact serotonin levels as well. 

Symptoms of serotonin syndrome include confusion, insomnia, high blood pressure, dilated pupils, trembling, profuse sweating, diarrhea, and muscle twitching. In serious cases, high fever, abnormal heartbeat, seizures, muscle rigidity, and unconsciousness can occur. Untreated serotonin syndrome can be lethal. Discontinuing a drug that causes symptoms may cause mild versions of serotonin syndrome to fade away within a couple of days. A greater risk of serotonin syndrome is associated with taking a higher dose of a single drug, multiple drugs, herbal supplements, or illicit drugs that increase serotonin. 

Mild side effects

When administered as tablets or nasal spray, Imitrex can cause mild adverse effects that disappear within a few days to a couple of weeks. These include a burning or "pins and needles" sensation on the skin, sleepiness, and vertigo. Some people on tablets or injections of Imitrex may feel cold or warm, become very tired, experience jaw or neck pain, or sense tightness, heaviness, or pressure in the chest. Injection site reactions include bleeding, bruising, redness, and swelling. Others who use the nasal spray may experience an unpleasant taste in the mouth or an uncomfortable sensation in the nose, sinuses, or throat. The Imitrex nasal spray can cause nausea and vomiting as well.

It's important for people on Imitrex to be mindful of any side effects of Imitrex. For example, people who become sleepy with Imitrex — a common occurrence — must be cautious about partaking in activities such as driving or using machinery. Some people, particularly the elderly, may get dizzy or faint if they stand or sit up too fast. Keeping track of headaches and medication with a diary is advised. Overuse of migraine medicine can make the condition worse. 

Some less common adverse effects caused by Imitrex include changes in color vision or hearing, insomnia, painful or swollen joints, sensitivity to UV rays from sunlight, heartburn, and poor concentration.

Serious side effects

Though uncommon, serious side effects from Imitrex may need emergency medical treatment. For example, a person may suffer a heart attack, stroke, or have a seizure. A severe allergic reaction can occur, causing shortness of breath or swelling of the tongue, mouth, or throat. Other serious effects include irregular heartbeat, a spike in blood pressure, and rebound headaches. 

Some people on Imitrex may develop Raynaud's syndrome, where blood flow to the extremities is diminished. This causes numbness and pain as well as color changes (white to blue to purple) in the fingers and toes. Weight loss, severe stomach pain, bloody diarrhea, constipation, and fever can result from decreased blood flow to the stomach and intestine. 

Some severe symptoms may occur as a consequence of serotonin syndrome. Among these symptoms are rapid heartbeat, sweating, muscle stiffness, loss of balance, restlessness, and hallucinations. Though usually mild, injection reactions can be more concerning if they involve intense soreness or swelling, or if they persist beyond a few days. 

Oral dosage

For oral use, Imitrex is comes in 25-, 50-, or 100-mg single doses for adults, per the Mayo Clinic. It is taken with or without food according to the prescribing doctor's instructions. Imitrex should be taken at the first sign of actual headache pain, not when flashing lights or other warning signs appear. Regular doctor visits are important to assess the drug's effectiveness. A doctor should also be notified if the medicine did not work or caused a worsening or more frequent occurrence of headaches. An alternative medication should be available if Imitrex does not provide headache relief. If a headache returns after relief with the first dose, a second dose can be taken, but no sooner than two hours following the initial dose, notes WebMD. The maximum dose of Imitrex per day is 200 mg. Imitrex tablets may also be prescribed as a home backup treatment for injection of the medication under the skin. 

Proper storage and disposal of Imitrex is important, notes MedlinePlus. Tablets should be protected from heat and moisture by closing bottles securely and avoiding storage in the bathroom. Keeping the medication out of sight and reach of children is vital since they can easily open containers such as pill organizers. Care should also be given to the expedient disposal of unneeded tablets so that they are inaccessible to children or pets. However, tablets should never be flushed down the toilet. Ideally, unused tablets should be disposed of through a medicine take-back program. 

Nasal spray dosage

Imitrex nasal spray comes in single doses of 5, 10, or 20 mg for adults (via DailyMed). Some people may use their first dose of nasal spray in a medical setting. While the 20-mg dose is the most effective, it carries a higher risk of side effects. The 10-mg dose is given by spraying each nostril with a single 5-mg dose, while the 5-mg and 20-mg doses are sprayed into one nostril. Dosages should not be changed without first consulting the prescribing physician. As with the Imitrex tablets, an additional dose of the Imitrex spray can be given at least two hours following the first nasal spray, if necessary and at your doctor's discretion. The maximum daily dose of Imitrex nasal spray is 40 mg. Since each sprayer contains one dose of Imitrex, it should not be tested before use. Imitrex nasal spray should be stored in a cool, dark location. 

Injection dosage

Unlike the tablets or nasal spray that are only approved for migraines, injectable Imitrex can be used to treat cluster headaches as well as migraines, per DailyMed. Though Imitrex can be injected at any time during a headache, it's best given at the onset of a migraine or cluster headache attack. Injectable Imitrex comes in 4-mg or 6-mg single-dose prefilled syringe cartridges that are used with an autoinjector device (Imitrex STAT dose Pen). If an initial 6-mg dose has some effect, a second 6-mg dose can be injected at least an hour later. The maximum daily dose is 12 mg per day. Detailed instructions are given to people who are able to self-administer injectable Imitrex without medical supervision. Some people may need to take their first Imitrex injection in a medical setting. 

Imitrex is injected under the skin in an area of fatty tissue. The site should have skin thick enough to accommodate needle penetration of about a quarter of an inch, so will usually be in the upper arms or thighs. Imitrex should not be injected into a muscle or vein. 

Imitrex use in pregnant and breastfeeding people

The safety and effectiveness of Imitrex for pregnant women has not been evaluated in clinical trials, notes Medical News Today. In an observational study conducted between 1996 and 2012, health information was collected on outcomes of infants exposed to Imitrex during gestation. The data did not indicate an increased frequency of birth defects resulting from Imitrex exposure. Other population studies compared pregnancy outcomes in women who used Imitrex during pregnancy and in those who did not. No increase in the risk of birth defects was associated with use of Imitrex. In contrast, toxicity studies have shown that administering Imitrex to pregnant animals resulted in birth defects. Ultimately, pregnant women considering the use of Imitrex to treat migraines should discuss the risks with their physician. 

Since, as in pregnant women, no studies have been performed on the use of Imitrex in lactating women, its safety for use by women who are breastfeeding is uncertain as well. Though the drug is excreted into breast milk, its effects on the breastfed infant are unknown. Avoiding breastfeeding for 12 hours after taking Imitrex will reduce the infant's exposure to the drug. 

Imitrex for inflammation

According to a 2021 systematic review published in the journal Drug Development Research, sumatriptan (Imitrex) not only functions as a pain reliever for migraines, but wields anti-inflammatory activity as well. Studies have shown that low doses of sumatriptan can suppress markers of inflammation such as tumor necrosis factor-alpha (TNF-alpha) and nuclear factor-kappa B — a master regulator of inflammatory responses in the body. Animal models of various inflammatory conditions suggest a protective effect from sumatriptan. These conditions include spinal cord injury, mouth and skin inflammation, and ischemia-reperfusion injury (tissue damage resulting from restoration of blood flow after a temporary blockage). Since low doses of sumatriptan are effective, it may be used as a safer alternative to steroids and other immunosuppressive drugs.  

Pain emanating from inflamed internal organs is often treated with opioid medications, per a study published in a 2008 edition of Gastroenterology. However, their use is limited by constipation and other side effects as well as the risk of addiction and dependence. When sumatriptan is used to treat migraines, it targets specific serotonin receptors that are found throughout the nervous system and not just in the head. Thus, in addition to treating headache pain, the drug may potentially be used in lieu of opioid drugs to treat other types of pain. In fact, in an animal model of pancreatitis, sumatriptan was effective in suppressing pain associated with inflammation.