Timothy Grass Pollen Allergen Extract

What is Grastek?

Grastek (Timothy Grass pollen allergen extract) is a sublingual tablet used as a form of immunotherapy for the treatment of allergy symptoms (allergic rhinitis) caused by Timothy and related grasses. Timothy grass is a common grass in the U.S. and is also cross reactive with Orchard grass, Kentucky blue grass, meadow fescue, sweet vernal, and redtop grasses. Grastek is made by the drug company Merck and is available only by prescription.

Treatment of Timothy grass allergies with Grastek should be supervised by a physician, typically a specialist in allergies called an immunologist. Grastek works in the same manner as allergy shots but is less painful and more convenient. Grastek does not provide immediate relief of allergy symptoms but may decrease the severity of allergy symptoms over time in some individuals.

How is Grastek Taken?

As previously mentioned Grastek comes in the form of a sublingual tablet. The tablet is dissolved under the tongue. Grastek should not be taken with food, and you should not swallow for one minute after the tablet has dissolved. The first dose of Grastek is taken in your healthcare providers office so that you can be monitored for a serious allergic reaction. You should remain in your healthcare provider's office for at least 30 minutes after taking your first dose of Grastek. If no reaction occurs Grastek can then be taken at home as a once daily dose.

Treatment with Grastek should be initiated at least 12 weeks before the onset and continue throughout the grass allergy season. Due to the risk of severe allergic reaction or anaphylaxis with immunotherapy all individuals who use Grastek should also be given a prescription for auto-injectable epinephrine and instructed on it's use as well as the signs and symptoms of a severe allergic reaction or anaphylaxis.

Who Can Take Grastek?

Grastek is only effective for individuals who have confirmed allergies to Timothy or related grasses. This must be confirmed via positive skin test, or positive blood tests for IgE antibodies. It is approved for individuals aged 5-65 years.

Grastek should not be taken by individuals who have severe or unstable asthma. It should also not be taken by individuals with a history of eosinophilic esophagitis, severe allergic reaction or anaphylaxis. You should notify your doctor of any health conditions you have as well as any medications you are taking before starting Grastek.

Notify your doctor if you are pregnant or breastfeeding before taking Grastek. Grastek is a pregnancy category B medication and it is not currently known if Grastek is excreted in breastmilk.

Side Effects of Grastek

The most commonly reported side effects that were reported with the use of Grastek were: itching (specifically of the ears, mouth, and tongue), mouth edema and throat irritation.

Less commonly reported side effects included: headache, dry throat, throat tightness, nasal discomfort, dyspnea, nausea, chest discomfort, fatigue, urticaria, glossodynia, and tongue disorders.

This list is not all inclusive.

As previously mentioned, a serious allergic reaction or even anaphylaxis can occur with the use of Grastek. If you experience symptoms of an anaphylactic reaction you should use injectable epinephrine as instructed and seek immediate medical attention.

Sources: Grastek. Accessed: May 28, 2015 from FDA Approves Merck's Grastek Sublingual Tablet as Immunotherapy to Grass Pollen Induced Allergic Rhinitis with or without Conjunctivitis in Children and Adults. Accessed: May 28, 2015 from Grastek Prescribing Information. Accessed: May 28, 2015 from

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